Fossil cast of a fin from a juvenile Sauripterus taylori, a late Devonian fish with primitive features of tetrapods. (Image: Matt Wood)
Research on fossilized fish from the late Devonian period, roughly 375 million years ago, details the evolution of fins as they began to transition into limbs fit for walking on land.
The new study by paleontologists from the University of Chicago, published this week in the Proceedings of the National Academy of Sciences, uses CT scanning to examine the shape and structure of fin rays while still encased in surrounding rock. The imaging tools allowed the researchers to construct digital 3D models of the entire fin of the fishapod Tiktaalik roseae and its relatives in the fossil record for the first time. They could then use these models to infer how the fins worked and changed as they evolved into limbs.
Much of the research on fins during this key transitional stage focuses on the large, distinct bones and pieces of cartilage that correspond to those of our upper arm, forearm, wrist, and digits. Known as the “endoskeleton,” researchers trace how these bones changed to become recognizable arms, legs and fingers in tetrapods, or four-legged creatures.
The delicate rays and spines of a fish’s fins form a second, no less important “dermal” skeleton, which was also undergoing evolutionary changes in this period. These pieces are often overlooked because they can fall apart when the animals are fossilized or because they are removed intentionally by fossil preparators to reveal the larger bones of the endoskeleton. Dermal rays form most of the surface area of many fish fins but were completely lost in the earliest creatures with limbs.
“We’re trying to understand the general trends and evolution of the dermal skeleton before all those other changes happened and fully-fledged limbs evolved,” said Thomas Stewart, PhD, a postdoctoral researcher who led the new study. “If you want to understand how animals were evolving to use their fins in this part of history, this is an important data set.”
Seeing ancient fins in 3D
Stewart and his colleagues worked with three late Devonian fishes with primitive features of tetrapods: Sauripterus taylori, Eusthenopteron foordi and Tiktaalik roseae, which was discovered in 2006 by a team led by UChicago paleontologist Neil Shubin, PhD, the senior author of the new study. Sauripterus and Eusthenopteron were believed to have been fully aquatic and used their pectoral fins for swimming, although they may have been able to prop themselves up on the bottom of lakes and streams. Tiktaalik may have been able to support most of its weight with its fins and perhaps even used them to venture out of the water for short trips across shallows and mudflats.
“By seeing the entire fin of Tiktaalik we gain a clearer picture of how it propped itself up and moved about. The fin had a kind of palm that could lie flush against the muddy bottoms of rivers and streams,” Shubin said.
Stewart and Shubin worked with undergraduate student Ihna Yoo and Justin Lemberg, PhD, another researcher in Shubin’s lab, to scan specimens of these fossils while they were still encased in rock. Using imaging software, they then reconstructed 3D models that allowed them to move, rotate and visualize the dermal skeleton as if it were completely extracted from the surrounding material.
The models showed that the fin rays of these animals were simplified, and the overall size of the fin web was smaller than that of their fishier predecessors. Surprisingly, they also saw that the top and bottom of the fins were becoming asymmetric. Fin rays are actually formed by pairs of bones. In Eusthenopteron, for example, the dorsal, or top, fin ray was slightly larger and longer than the ventral, or bottom one. Tiktaalik’s dorsal rays were several times larger than its ventral rays, suggesting that it had muscles that extended on the underside of its fins, like the fleshy base of the palm, to help support its weight.
“This provides further information that allows us to understand how an animal like Tiktaalik was using its fins in this transition,” Stewart said. “Animals went from swimming freely and using their fins to control the flow of water around them, to becoming adapted to pushing off against the surface at the bottom of the water.”
Stewart and his colleagues also compared the dermal skeletons of living fish like sturgeon and lungfish to understand the patterns they were seeing in the fossils. They saw some of the same asymmetrical differences between the top and bottom of the fins, suggesting that those changes played a larger role in the evolution of fishes.
“That gives us more confidence and another data set to say these patterns are real, widespread and important for fishes, not just in the fossil record as it relates to the fin-to-limb transition, but the function of fins broadly.”
The study, “Dorsoventral asymmetry in the dermal rays of tetrapodomorph paired fins,” was supported by the Brinson Foundation, the Academy of Natural Sciences, the University of Chicago Biological Sciences Division and the National Science Foundation. Additional authors include Natalia Taft from the University of Wisconsin — Parkside and Edward Daeschler from Drexel University.
Reference:
Thomas A. Stewart, Justin B. Lemberg, Natalia K. Taft, Ihna Yoo, Edward B. Daeschler, Neil H. Shubin. Fin ray patterns at the fin-to-limb transition. Proceedings of the National Academy of Sciences, 2019; 201915983 DOI: 10.1073/pnas.1915983117
The cruise is led by Ursula Röhl of MARUM (left) and Debbie Thomas of Texas A&M University (right). They are supported by the Expedition Project Manager Laurel Childress. Photo: SIEM offshore
The Earth’s Cenozoic Era began 66 million years ago with a bang—and with the last mass extinction event on Earth until now. The meteorite impact that marked the end of the Cretaceous Period and the beginning of the Cenozoic Era was followed by a number of dramatic global events, including a heat pulse 56 million years ago. Only after this remarkable boundary did mammals develop the diversity that we know today. The climate had cooled continuously over a long period of time. During this time the environmental conditions, ocean temperatures, ocean circulation, and wind patterns also changed fundamentally. In order to better understand each of these climatic events and the overall development of climate, it is necessary to have records of the Earth’s climate that are as complete and high-resolving as possible. It is especially important that these records include locations that play a key role in understanding the environmental conditions, ocean circulation and wind patterns at higher latitudes.
Zooming in on climate development
This is where the objectives of the upcoming Expedition 378 in the Southwest Pacific by the drilling vessel JOIDES RESOLUTION within the framework of the International Ocean Discovery Program (IODP) will have a significant impact. Using the deposits on the seafloor, the expedition team will produce detailed reconstructions of how the climate changed during the Cenozoic. This will include, for example, how the elevated global temperatures and the heat transport to the polar regions could be sustained 56 million years ago. It was warm all over the Earth; compared to the situation today, there was practically no temperature difference between the polar regions and the tropics, even though the solar radiation was no more intense than it is today.
The cruise is being led by Dr. Ursula Röhl of MARUM, the Center for Marine Environmental Sciences of the University of Bremen and Dr. Debbie Thomas of Texas A&M University (USA). It begins in January, will last almost five weeks, and ends in Papeete on Tahiti in February.
Return to the source of the first temperature curve
The primary goal, according to the expedition plan, is to drill several holes at a site from the predecessor program of IODP that was drilled in March 1973 at a water depth of 1,200 meters, but which only retrieved spot cores. “The temperature curve that was produced from this hole was one of the first ever constructed and, despite the sparse sampling, was able to illustrate for the first time characteristic climate fluctuations in the Cenozoic,” explains Ursula Röhl. Over the past 47 years, however, both the drilling techniques and the analytic methods have improved. “Returning to this location means that we can link to the source of this very first temperature curve for the Cenozoic Era.” This time there will be contiguous coring in an even deeper hole. A depth of up to 670 meters into the seafloor has been approved. By this depth the scientists hope to be able to verify all of the climatic events of the Cenozoic. Says Ursula Röhl, “We want to obtain as complete and high-quality a record as possible.”
Precise ages of the sediment deposits will be determined directly on board based on microfossils. This allows researchers to identify the meteorite impact at the Cretaceous-Paleogene boundary as well as the transitions from the Paleocene to the Eocene (Paleocene-Eocene Thermal Maximum—PETM) with an age of 56 million years and from the Eocene to Oligocene at 33.9 million years ago. The PETM is characterized by an abrupt release of large amounts of carbon that triggered a rapid temperature rise—a massive global heat pulse. The transition from the Eocene to Oligocene reflects strong global cooling and initiation of the permanent ice cover in Antarctica, and is therefore another important time interval in the Earth’s climate history.
The drill cores should improve our understanding of the climate events of the Cenozoic, especially in the subpolar region, including the structure of the ocean and the biogeochemical cycle. The shells of microfossils in the sediments contain chemical signatures of past climate conditions that are as unique as fingerprints. Based on the new information, researchers will be able to draw conclusions about the strength of oceanic upwelling and winds throughout millions of years, and make more precise statements about atmospheric and oceanic subsystems of the Earth’s climate.
“The sediments that we obtain will provide crucial data on ocean temperatures and the carbon cycle for the vast region of the southwestern Pacific. This new knowledge will lead to great advances in our understanding of climate dynamics during the warm periods,” adds co-chief scientist Debbie Thomas.
Due to a last-minute mechanical issue that developed shortly before departure, the expedition duration was shortened from nine to five weeks. This means that it will not be possible to drill at Point Nemo, the Pacific pole of inaccessibility, as originally planned. But at the same time, this will provide the team of researchers from twelve countries with the possibility to retrieve a complete sequence of sediments through the drilling of additional holes.
The magnitude of the Great Lisbon Earthquake event, a historic and devastating earthquake and tsunami that struck Portugal on All Saints’ Day in 1755, may not be as high as previously estimated.
In his study published in the Bulletin of the Seismological Society of America, Joao F. B. D. Fonseca at the Universidade de Lisboa used macroseismic data—contemporaneous reports of shaking and damage—from Portugal, Spain and Morocco to calculate the earthquake’s magnitude at 7.7. Previous estimates placed the earthquake at magnitude 8.5 to 9.0.
Fonseca’s analysis also locates the epicenter of the 1755 earthquake offshore of the southwestern Iberian Peninsula, and suggests the rupture was a complicated one that may have involved faulting onshore as well. This re-evaluation could have implications for the seismic hazard map of the region, he said.
The current maps are based on the assumption that most of the region’s crustal deformation is contained in large offshore earthquakes, without a significant onshore component. “While the current official map assigns the highest level of hazard to the south of Portugal, gradually diminishing toward the north, the interpretation now put forward concentrates the hazard in the Greater Lisbon area,” said Fonseca.
The 1755 Lisbon earthquake and tsunami event, along with the fires it caused that burned for hours in the city, is considered one of the deadliest earthquake events in history, leading to the deaths of about 12,000 people. The devastation had a significant impact on Portugal’s economy and its political power within Europe, and its philosophical and theological implications were widely discussed by Enlightenment scholars from Voltaire to Immanuel Kant.
The widespread devastation led earlier seismologists to estimate a high magnitude for the earthquake. With modern modeling techniques and a better understanding of the region’s tectonics, Fonseca thought it important to revisit the estimate. The 1755 earthquake is unusual in that it produced extreme damage hundreds of kilometers from its epicenter without any of the accompanying geological conditions—like amplification of seismic waves in a loose sedimentary basin, for instance—that normally cause such severe site effects.
“Explanations put forward for the extreme damage in Lisbon tend to invoke abnormally low attenuation of seismic energy as the waves move away from the epicenter, something that is not to be observed anywhere else in the globe,” Fonseca explained. “Current attempts to harmonize seismic hazard assessment across Europe are faced with large discrepancies in this region, which need to be investigated and resolved for a better mitigation and management of the risk through building codes and land use planning.”
Fonseca used 1206 points of macroseismic data to reassess the 1755 earthquake’s magnitude and epicenter. The analysis and modeling also indicate that some of the very high earthquake intensities reported in the region’s nearby Lower Tagus Valley and the Algarve may have been due to two separate onshore earthquakes in these locations. These earthquakes, which took place a few minutes after the offshore rupture, may have been triggered by the first earthquake, Fonseca suggests.
The new magnitude estimate for the 1755 earthquake is similar to that of another large regional earthquake, the 1969 magnitude 7.8 Gorringe Bank quake. However, the damage from the Gorringe Bank earthquake was much less severe, possibly in part because the onshore faults had not accumulated enough stress to make them “ripe to rupture,” Fonseca says. “The Lower Tagus Fault, near Lisbon, ruptured in 1909, in 1531 and likely in 1344. It is plausible that it was good to go in 1755, but still halfway through the process of accumulating stress in 1969.”
Fonseca also suggests that the destructive size of the 1755 accompanying tsunami might be due more to the presence of a large sedimentary body produced by past subduction, called an accretionary wedge, on the ocean bottom in the Gulf of Cadiz. When a fault rupture moves through this wedge, it can generate a tsunami even without an extreme magnitude rupture, he said.
Reference:
Joao F. B. D. Fonseca. A Reassessment of the Magnitude of the 1755 Lisbon Earthquake. Bulletin of the Seismological Society of America (2020) DOI: 10.1785/0120190198
Gachala Emerald. Photo by Chip Clark/Smithsonian Institution
The Gachala Emerald was discovered in 1967 in the mine called Vega de San Juan, located in Gachala, a town in Colombia, 142 km (88 mi) from Bogota. It is one of the most precious and popular emeralds in the world. Gachalá Chibcha means “Gacha’s spot.” Today, the emerald is in the United States, where the New York City jeweler, Harry Winston, donated it to the Smithsonian Institution.
The more pure green color the emerald displays, the more valuable it is. Its color is caused by impurity atoms of either chromium or vanadium, which are incorporated into beryl crystals as they grow.
The emerald was named in honor of Gachalá, the municipality of Cundinamarca where it was found
Characteristics of Gachalá Emerald
Shape: Emerald
Color: Intense green
Carats: 858 Carats
Weight: 172 grams
Size: 5 centimeters
Year of extraction: 1967
The “Gachala Emerald” is a thin hexagonal prism with a height of 5 cm and a diameter of almost the same length, which conforms to the normal crystal habit of the emeralds. At the upper end of the crystal, the hexagonal form of the crystal is more apparent, but it is not a regular hexagon with two opposite sides of the hexagon shorter than the other four sides. Even on the sides of the crystal, the six sides of the crystal can be marked, although from the sides the crystal appears more cubical than hexagonal. The crystal color is a pure dark green, and it appears that the crystal is opaque. We may not be able to say anything about the gemstone’s diaphaneity unless the crystal is polished. Nevertheless, it is well known that with enhanced brightness, most Gachala emeralds have strong clarity and shine. One of the world’s largest gem-quality emerald crystals, the “Gachala Emerald.”
Where was the Gachala emerald found?
In 1967, the 858ct Gachala Emerald crystal was discovered in Gachala, Colombia, at the Vega de San Juan mine. These scale and superb color emerald crystals are rarely preserved; they are usually cut into gems. Harry Winston gave the Smithsonian the Gachala Emerald in 1969.
Gachala Emeralds Special Features
Generally speaking, gachala emeralds are finer, with less defects and inclusions than emeralds from other Colombian mines like Muzo, Coscuez and Chivor. For strong visibility, transparency and brightness, the emeralds are usually “brow clean.” Their color is typically pale green, though. The darker vivid green colors, despite the presence of inclusions, command the highest prices compared to the pale green but much cleaner stones, is a crucial factor in emerald color that defines their value. Sadly, the best green colors tend to be the most included in the emeralds.
The Gachala Emerald exhibited at the Tucson Show of February 2003
At the 49th Tucson Gem & Mineral Society exhibition in February 2003, the “Gachala Emerald” was displayed. Michael Scott, former president of Apple Computer Company, who is also a collector and connoisseur of gemstones and minerals, opened the show from 13 to 17 February with an evening reception and chat. The theme of the 2003 exhibition was the “Minerals of the Andes.” The display was attended by several private collectors and museums, which displayed a great collection of specimens of Andes origin as well as from other sources.
The exhibition was a spectacular success, with one of the best ever being said to be the variety of exhibits shown. The exhibition was attended by about two dozen museums and pulled out their best exhibits. The Star attraction among the displays shown by the Smithsonian Institution’s National Museum of Natural History was the 858-carat “Gachala Emerald,” of Andean origin, which was exhibited in tandem with the famous Marjorie Merriweather Post emerald necklace, also of Colombian origin, with 24 baroque polished round emeralds. Two proustites, a Bolivian phosphophyllite crystal accompanied by a faceted diamond of 26.9 carats, and other unusual specimens such as franckeite, andorite, helvite, and canfieldite were among the other mineral specimens of Andean origin displayed by the Smithsonian Institution.
Michael Scott, Gene and Roz Meieran, Bill Larson, Rock Currier, Steve and Clara Smale and W were among the private collectors who showed impressive exhibits that gained much attention. There’s R. Danner.
The Gachala Emerald is exhibited at the Smithsonian’s NMNH
As part of the National Gem Collection, the “Gachala Emerald” is now on display at the Janet, Annenberg Hooker Hall of Geology, Gems and Minerals, the Smithsonian National Museum of Natural History, along with other famous emeralds such as the Mackay Emerald Necklace, the Hooker Emerald Brooch, the Chalk Emerald Ring, the Maximilian Emerald Ring, the Spanish Inquisition Necklace and others.
Agate is a gemstone used in different pieces of decoration and jewelry. It’s made of silica and chalcedony. The silica crystals, mostly Chalcedony, form a brightly colored grainy stone known by the people as Agate. It was given the name “Agate” after the river “Achates” where it was first found once. In southwestern Sicily, Achates is situated.
It’s found mostly in volcanic rocks or lavas. Agate is powerful in filling the cracks in volcanic rocks once the lava bursts from them. When agate is transversally sweet, it depicts a parallel line network. Such lines appear slightly on the surface and tend to divide agate into various sections. Agate is known as banded agate with such lines.
Types of Agate
Onyx Agate
Black Onyx Agate Stone Slab Slice 4
Onyx specifically refers to silicate mineral chalcedony’s parallel banded form. Agate and onyx are both layered chalcedony varieties which differ only in band form: agate has curved bands and onyx has parallel bands. His bands ‘ colors range from black to nearly any color. Onyx specimens usually contain bands of black and/or white. Onyx has also been applied as a descriptive term to parallel banded alabaster, marble, obsidian and opal types, and misleadingly to contorted banding materials such as “Cave Onyx” and “Mexican Onyx.”
Onyx comes through Latin (of the same spelling), from the Greek ὄνυξ, meaning “claw” or “fingernail”. Onyx with flesh-colored and white bands can sometimes resemble a fingernail. The English word “nail” is cognate with the Greek word.
Onyx is formed of bands of chalcedony in alternating colors. It is cryptocrystalline, consisting of fine intergrowths of the silica minerals quartz and moganite. Its bands are parallel to one another, as opposed to the more chaotic banding that often occurs in agates.
Sardonyx Agate
Agate Sardonyx Chalcedony Quartz Cabochon Lucky Stone 39.00ct
It is a variant in which the colored bands are sard (shades of red) rather than black. Black onyx is perhaps the most famous variety, but is not as common as onyx with colored bands. Artificial treatments have been used since ancient times to produce both the black color in “black onyx” and the reds and yellows in sardonyx. Most “black onyx” on the market is artificially colored.
It looks very beautiful and delicate in banding, as the name suggests. Iris doesn’t mean it looks like the human iris. The name was given to her because of the colors of the rainbow. Iris is used in the rainbow as well. It is finely banded with a vibrant color display. You will see it reflecting the light while you hold it opposite to the sun. The light touches and reflects the thin bands within it.
Crazy Lace Agate
Crazy Lace Agate, Sierra Santa lucia, Ejido Benito Juarez, Chihuahua, Mexico, Size : 29 x 5 x 39mm. Credit: Kristalle
Crazy lace agate (also known as Mexican Agate) is a banded chalcedony (microcrystalline quartz) that’s infused with iron and aluminum and is often brightly colored and complexly patterned. This produces the creamy browns, blacks, greys and golds (and occasional pinks or reds) swirled together in this stone.
The white-colored banded Chalcedony makes it more attractive. Other layers can be brown, cream, black or gray in different colors. Some Crazy Lace Agate comes in colored bands of yellow, orange, golden and red. Occasionally, because of its multiple colors and light reflecting nature, the jewelers call it “Earth rainbow.”
Thunder-egg
Thunder Egg
A Thunder Egg “Thunderegg” is a nodule-like rock, similar to a filled geode, that is formed within rhyolitic volcanic ash layers. Thundereggs are rough spheres, most about the size of a baseball—though they can range from less than an inch to over a meter across. They usually contain centres of chalcedony which may have been fractured followed by deposition of agate, jasper or opal, either uniquely or in combination. Also frequently encountered are quartz and gypsum crystals, as well as various other mineral growths and inclusions.
Thundereggs usually look like ordinary rocks on the outside, but slicing them in half and polishing them may reveal intricate patterns and colours. A characteristic feature of thundereggs is that (like other agates) the individual beds they come from can vary in appearance, though they can maintain a certain specific identity within them.
Enhydro Agate
Enhydro Agate. Locality : Brasil. Size 13.5×11.6 cm. Credit: Didier Descouens
Enhydro agates are nodules, agates, or geodes with inside their cavity trapped in water. Enhydros are closely related to the inclusion of fluids, but consist of chalcedony. Enhydros formation remains an ongoing process, with specimens from the Eocene Epoch. We are frequently found in volcanic rock areas.
Enhydro agates are made up of banded microcrystalline or cryptocrystalline quartz. The agate has a hollow center, partially containing water. Enhydro agates can also contain debris or petroleum. Because the cavity is not full, the agate can produce sound from being shaken. Agates vary in size. The largest recorded agate was found in Fuxin City, China, with a diameter of 63 cm and weighing 310 kg.
Enhydros are formed when water rich in silica percolates through volcanic rock, forming layers of deposited mineral. As layers build up, the mineral forms a cavity in which the water becomes trapped. The cavity is then layered with the silica-rich water, forming its shell. Unlike fluid inclusions, the chalcedony shell is porous, allowing water to enter and exit the cavity very slowly. The water inside of an enhydro agate is most times not the same water as when the formation occurred. During the formation of an enhydro agate, debris can get trapped in the cavity. Types of debris varies in every agate.
Polyhedroid Agate
Polyhedroid Agates from Pariaba, Brazil
This type of agate has flat sides and is very similar to polyhedron in the color scheme. The layers of condensed polygons can be seen inside when cut from the middle. It is usually found in the state of Paraiba, Brazil. The crystals inside, when held against the sun, reflect the light and discharge beautiful rays.
Moss Agate
Moss Agate. Locality: TRENGGALEK, INDONESIA. SIZE : 25X17X6 mm. Credit: gem rock auctions
Moss agate is a semi-precious gemstone formed from silicon dioxide. It is a form of chalcedony which includes minerals of a green colour embedded in the stone, forming filaments and other patterns suggestive of moss. The field is a clear or milky-white quartz, and the included minerals are mainly oxides of manganese or iron. It is not a true form of agate, as it lacks agate’s defining feature of concentric banding. Moss agate is of the white variety with green inclusions that resemble moss. It occurs in many locations. The colors are formed due to trace amounts of metal present as an impurity, such as chrome or iron. The metals can make different colors depending on their valence (oxidation state).
Despite its name, moss agate does not contain organic matter and is usually formed from weathered volcanic rocks.
Montana moss agate is found in the alluvial gravels of the Yellowstone River and its tributaries between Sidney and Billings, Montana. It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity. In Montana moss agate the red color is the result of iron oxide and the black color is the result of manganese oxide.
The Lake Superior Agate
The Lake Superior Agate. Photo by Lech Darski
The Lake Superior agate is a type of agate stained by iron and found on the shores of Lake Superior. Its wide distribution and iron-rich bands of color reflect the gemstone’s geologic history in Minnesota, Wisconsin, and Michigan. In 1969 the Lake Superior agate was designated by the Minnesota Legislature as the official state gemstone.
The Lake Superior agate was selected because the agate reflects many aspects of Minnesota. It was formed during lava eruptions that occurred in Minnesota about a billion years ago. The stone’s predominant red color comes from iron, a major Minnesota industrial mineral found extensively throughout the Iron Range region. Finally, the Lake Superior agate can be found in many regions of Minnesota as it was distributed by glacial movement across Minnesota 10,000 to 15,000 years ago.
Condor Agate
Condor Agate. Credit: Captain Tenneal
Condor agate was discovered and named by Luis de los Santos in 1993. It is found in the mountains near San Rafael, in Mendoza Province, Argentina. This agate exhibits colorful bands and patterns, and has become a popular stone among collectors and jewelry designers.
n the early days of condor agate collecting, a typical month of effort would yield 1 ton of good agates. Currently, excavation is required to find the agates, so an extra effort is needed to supply the ever growing demand for these gems. Initially, the agates were found scattered loose over the landscape and were readily harvested in quantity. Today, surface collecting is no longer prolific, so these agates are collected from shallow diggings in the cold agate fields in Mendoza province, Argentina.
Sagenite Agate
Golden Sagenite Needles in Very Clear Agate Mexico. Credit: ROBERT / VIKKI
It is formed by mixing Chalcedony with various minerals. The golden hair-like pointed lines make it more attractive and distinctive in its style.
Fortification Agate
Fortification Agate
The name was given to it due to its sharp-edged bands. These bands resemble with a fortified castle with sharp angles. The array of white, light brown, orange, red and purple colors make it worthwhile.
Fairburn Agate
Fairburn Agate. Locality: South Dakota, USA. Credit: Captain Tenneal
It is a rare, but very beautiful type of agate found in Fairburn, Custer Co., South Dakota, USA. It is considered to be the state jewel of South Dakota, USA. That’s why when you break into two pieces you can see the beautiful patterns of colors and designs. When found naturally, the surface is rough.
Botswana Agate
Botswana Agate
It is a unique agate available in dark and light gray and pink shades. However, some layers come with muted brown color.
Dendritic Agate
Dendritic Agate
It’s called the Plentitude Stone. It is considered to be the most valuable form of agate. Dendritic agate is associated with the ancient dryads of Greece. This type of agate is, therefore, a sign of good luck and the farmers use it to bury it in their fields to get the good crops.
Something like this goes through the formational process. First crystals grow in the gas cavity left in the volcanic andesite rock (in the case of the Coyamito Agate, these crystals are assumed to be aragonite). The agate then begins to form, cover the crystals and the cavity’s within. The more agate the coating on the crystals forms the thicker. This process can continue until the gas cavity is filled or, more often than not, the nodule leaves a hollow portion. Quartz or agate can, like all nodular agates, move from one to the other.
Opals are made out of rhyolite, basalt, sandstone, marl and rhyolite. A common source of opals are rhyolite geodes. The rocks, which means they have no properties of crystals, are known as mineraloids. It’s a silicon dioxide crystal-like product that is placed in cracks and cracks in rock at a somewhat low temperature.
Opals are also a gel high in a liquid content ranging from 3 to 30 percent water, but the opal gel acts as a solid. They’re essentially a silica spray! They can be quite cool and fragile, making it hard to hold them for jewelry after mounting.
Types of opals include: common and precious opals. Oregon opals include the types, rainbow, ryalite, contra luz, hydrophane, crystal, fire, blue, and dendritic.
Where to Find Opals in Oregon?
Baker County
Conner Creek Mining District “Baker Co.”
Swayze Creek “Baker Co.”
Clackamas County
Clackamas River localities “Clackamas Co.”
Oak Grove Fork “Clackamas Co.”
Columbia County
Neer Road, Goble “Columbia Co.”
Crook County
Howard Mining District (Ochoco Mining District; Bolivar Mining District) “Crook Co.”
Deschutes County
Newberry Caldera, East Lake “Deschutes Co.”
Harney County
Pueblo Mining District (Denio Mining District) “Harney Co.”
Hood River County
Pucci drillhole “Hood River Co.”
Jackson County
Ashland Mining District “Jackson Co.”
Butte Creek Mining District “Jackson Co.”
Evans Creek Mining District “Jackson Co.”
Meadows Mining District “Jackson Co.”
Jefferson County
Richardson Ranch (Priday Ranch), Madras “Jefferson Co.”
Klamath County
Oregon Technical Institute Occurrence “Klamath Co.”
Summit Rock “Klamath Co.”
Lake County
Christmas Valley pit, Christmas Valley “Lake Co.”
Hart Mountain “Lake Co.”
Juniper Ridge Opal Mine “Lake Co.”
Oregon Sunstone public collection area, Plush “Lake Co.”
Spectrum Mine, Plush “Lake Co.”
Madera Occurrence, Quartz Mountain “Lake Co.”
Quartz Mountain Gold Deposit (Fremont; Quartz Mountain Property), Quartz Mountain “Lake Co.”
School Creek Prospect “Lake Co.”
Malheur County
Brandon Occurrence (Quartz Mtn.; Glassy Butte) “Malheur Co.”
Owyhee Dam, Lake Owyhee State Park “Malheur Co.”
Aurora Uranium Prospect, Opalite District (McDermitt District) “Malheur Co.”
Rome Zeolite Occurrence “Malheur Co.”
Sheaville Zeolite Occurrence “Malheur Co.”
Succor Creek “Malheur Co.”
Marion County
Breitenbush Hot Springs Cinnabar Occurrence, Santiam District (Elkhorn District) “Marion Co.”
Morrow County
Opal Butte “Morrow Co.”
Opals are found nearly everywhere in the world, but how are we going to get to Oregon and find those deep wonders? The Juniper Ridge Opal mine is the site of a major opal discovery and development that has been going on for 30 years before being abandoned. After spending two years discovering and taking over the abandoned claim in 1998, a father and son team, Ken and Chuck Oldham, formed a group of lapidaries and miners. They opened it for a form of mining called “fee dig” mining after mining the claim for years.
Fee Dig mining is simple! Pay a small fee, get a little training and a spot to mine, and take away whatever you find!
Opal Butte is a mountain top close to Hepner City in Morrow County, Oregon. There is a working mine in operation since 1988, but it has been known since the 1800s, when opals were not regarded as important. There is a mine in the West Coast Mining Company, marketing opals through its outlets.
Klamath County, Oregon hosts Opal Creekand Klamath Falls, where opals have been found. The Favell museum in Klamath falls actually boasts an arrowhead made of fire opal!
Cantera opal is a type of Fire opals that do not show play of color are sometimes referred to as jelly opals. Cantera means “quarry,” and such stones come from quarries at Magdalena, Queretaro and possibly other Mexican locations. Mexican opals are sometimes cut in their rhyolitic host material if it is hard enough to allow cutting and polishing. This type of Mexican opal is referred to as a Cantera opal. Also, a type of opal from Mexico, referred to as Mexican water opal, is a colorless opal which exhibits either a bluish or golden internal sheen.
How is Opal Formed?
Opal is formed by a silicon dioxide and water solution. When water runs down the earth, it takes silica from sandstone and brings it into cracks and voids, created by natural faults or decomposing fossils. This leaves behind a layer of silica as the water evaporates.
How Cantera Opal is formed ?
Cantera Opal is a gemstone formed from the “Rhyolite”. Rhyolite is a kind of “Igneous Rock”
These are only found in Mexico and type the same as the Australian boulder opals, but the host rock is ryolite rather than ironstone.
Where are Mexican fire opals mined?
Mexican opal is mined in the Mexican states of Queretaro, Hidalgo, Guerrero, Michoacan, Julisio, Chihuahua and San Luis Potosi.
Obsidian is a natural volcanic glass that is formed as an igneous rock that is extrusive.
Obsidian is formed by rapidly cooling felsic lava extruded from a volcano with limited growth in crystals. It is commonly found in the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) creates a high viscosity resulting in the production of natural glass from the lava after rapid cooling. This highly viscous lava’s inhibition of atomic diffusion explains the lack of crystal growth. Obsidian is rough, fragile, and amorphous, with very sharp edges breaking. It was used in the past for the manufacture of cutting and slicing equipment and was used experimentally as surgical scalpel blades.
Obsidian is mineral-like, but not a true mineral because it is not crystalline as a glass; however, it is too complex to be categorized as a mineral. It is classified as a mineraloid sometimes. While obsidian is usually dark in colour, similar to basalt-like mafic rocks, the composition of obsidian is extremely felsic. Obsidian mainly consists of SiO2 (silicon dioxide), typically 70% or more. With a similar composition, crystalline rocks include granite and rhyolite. Because obsidian is metastable on the surface of the Earth (the glass forms fine-grained mineral crystals over time), no obsidian older than the Cretaceous period has been found. The existence of water speeds up this process of obsidian. Although the newly formed obsidian has a low water content, usually less than 1 percent by weight, it is slowly hydrated to form perlite when exposed to groundwater.
How to Identify Obsidian?
How can you identify obsidian ? The lack of a crystalline structure indicates that obsidian is not a true mineral and causes extreme sharpness of the fracture surfaces. Since prehistoric times, obsidian has been used in cutting tools and is still used today in surgical scalpels.
Explore obsidian where cooling is rapid in the margins of lava flows. Glass Buttes in central Oregon is one of the best places to find obsidian in the U.S. Pieces of fist size can be found on the surface in abundance here.
Examine the obsidian’s general presence. It has a distinctive appearance of smooth glass. Obsidian is a frozen liquid that contains small amounts of mineral impurities.
See the color Because pure obsidian is usually dark, on rare occasions it may also be almost white.
Consider the effect of impurities on the obsidian color For examples, iron and magnesium may make obsidian dark green. Hematite or limonite add a red or brown color to the obsidian. A lot of microscopic rock and mineral particles usually cause the jet black color most closely associated with obsidian.
Looking at the obsidian’s visual effects of small gas bubbles. It can cause the obsidian to have a gold or silver shine if the bubbles were spread almost flat.
What does Obsidian feel like?
Obsidian has a strong conchoidal fracture and luster. It means that the top of the fracture is curving smoothly (like a seashell). Obsidian appears to be black. Minute inclusions and tiny crystals in the glass create it hue.
What are the characteristics of obsidian?
Obsidian breaks with a typical “conchoidal” fracture, like all glass and some other forms of natural rocks. Due to the near absence of mineral crystals in the glass, this smooth, curved form of fracture surface occurs. Conchoidal fracture surface intersections may be sharper than a knife.
What is the texture of obsidian?
Obsidian, igneous rock that occurs as a natural glass produced by the rapid refreshment of viscous volcanic lava. Obsidian is extremely silica-rich (around 65 to 80 percent), low in water, and has a rhyolite-like chemical composition. Obsidian has a luster of glass and is somewhat stronger than window glass.
Caves come in all sizes, shapes, and colors. Easy caves are typically defined by high ceilings and smooth floors. Credit: Jesse Barden
Lava Beds National Monument in Siskiyou and Modoc County is located in north east California. This monument is located at the northeast edge of Medicine Lake Volcano and is the largest volcano in the Cascade region.
The region in and around Lava Beds National Monument lies at the junction of the Sierra-Klamath, Cascade, and the Great Basin physiographic provinces. The monument was established as a national monument on November 21, 1925, and includes more than 46,000 acres (190 km2).
Lava Beds National Monument contains numerous lava tubes, 25 of which have marked entrances and established public access and exploration trails. The monument also provides paths through the xeric desert landscape of the high Great Basin and through the volcanic zone. The Modoc War was waged in 1872 and 1873, with a band commanded by Captain Jack (Kintpuash). The area in his memory was called Captain Jack’s Stronghold.
Lava Beds National Monument is geologically significant because of its wide variety of volcanic formations, including lava tubes, fumaroles, cinder cones, spatter cones, pit craters, hornitos, maars, lava flows, and volcanic fields.
Volcanic eruptions on the Medicine Lake shield volcano have created an incredibly rugged landscape punctuated by these many landforms of volcanism.
2. The Ice Age Flood Trail, Washington, Oregon and Idaho
The National Geologic Trail or Ice Age Floods Trail is known as the United States ‘ first National Geologic Trail. It will consist of a network of linking routes that will provide explanation of the geological effects of the last glacial period’s Glacial Lake Missoula floods that started around 110,000 years ago.
The National Park Service (NPS) commissioned an Environmental Assessment that found that Option 3 — setting up a “National Geological Trail — designating National Park Service Floods Pathways, with an Interagency Technical Committee including federal, tribal and state agencies and a Trail Advisory Committee to assist trail managers and staff” was the preferred optium. As a result, the Ice Age Floods Trail was created by the 2009 Omnibus Public Land Management Act, which allowed Congress to create the Ice Age Floods National Geologic Trail in parts of the states of Montana, Idaho, Washington, and Oregon, and formed the Trail’s NPS administration.
3. Mammoth Cave National Park, Kentucky
Mammoth Cave National Park, Kentucky
Mammoth Cave National Park is an American national park located in central Kentucky that includes parts of Mammoth Cave, the world’s longest known cave system. The system’s official name has been the Mammoth–Flint Ridge Cave System since the 1972 merger of Mammoth Cave with the even-longer system under Flint Ridge to the north. The park was established on 1 July 1941 as a national park, on 27 October 1981 as a World Heritage Site, and on 26 September 1990 as an international biosphere reserve.
The 52,830-acre park (21,380 ha) is mainly located in Edmonson County, with small areas spreading eastward to the counties of Hart and Barren. The Green River runs through the park, flowing into the Green just inside the park by a tributary named the Nolin River. Mammoth Cave is the longest known cave system in the world with more than 400 miles (640 km) of surveyed caves, which is almost twice as long as Mexico’s second-longest cave system, the Sac Actun underwater cave.
4. San Andreas Fault at the Carrizo Plain, California
Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia.
In the southeast of San Luis Obispo County, California, about 100 miles (160 km) northwest of Los Angeles, the Carrizo Plain is a large enclosed grassland plain, about 50 miles (80 km) wide and up to 15 miles (24 km) across. It includes the Carrizo Plain National Monument of 246,812 acres (99,881 ha) and is California’s largest single native grassland. It includes Painted Rock in the Carrizo Plain Rock Art Discontiguous District, which is listed on the National Register of Historic Places. In 2012 it was further designated a National Historic Landmark due to its archeological value. The San Andreas Fault cuts across the plain.
The Carrizo Plain extends northwest from the town of Maricopa, following the San Andreas Fault. Bordering the plain to the northeast is the Temblor Range, on the other side of which is California’s Central Valley. Bordering the plain to the southwest is the Caliente Range. The community of California Valley is in the northern part of the plain. The average elevation of the plain is about 2,200 feet (670.6 m). Soda Lake, a 3,000-acre (12 km2) alkaline lake, is in the center of the plain with the popular Painted Rock containing Chumash and Yokut rock art nearby. As the central depression in an enclosed basin, Soda Lake receives all of the runoff from both sides of the plain. At 5,106 feet (1,556 m), Caliente Mountain, southwest of the plain, stands as the highest point in San Luis Obispo County. The climate type of the Carrizo Plain is semi-arid grassland. No trees grow there and the annual rainfall is around 9 inches (230 mm) per year.
5. La Brea Tar Pits, California
The pit of oozing oil in downtown Los Angeles has been trapping animals and preserving their skeletons for at least 40,000 years. The museum at the tar pits displays the skeletons. Credit: (Catherine Karnow / Corbis)
La Brea Tar Pits are a group of tar pits around which Hancock Park was built in Los Angeles urban area. Natural asphalt (also called asphalt, bitumen, pitch, or tar-brea in Spanish) has for tens of thousands of years sprung up from the ground in this area. Often the tar is coated with dirt, leaves, or water. The tar has preserved the bones of trapped animals for many years. The George C. Page Museum is devoted to exploring the tar pits and exhibiting the animals that died there. La Brea Tar Pits is a National Natural Landmark listed.
Tar pits are composed of heavy oil fractions called gilsonite, which seeped from the Earth as oil. In Hancock Park, crude oil seeps up along the 6th Street Fault from the Salt Lake Oil Field, which underlies much of the Fairfax District north of the park.[2] The oil reaches the surface and forms pools at several locations in the park, becoming asphalt as the lighter fractions of the petroleum biodegrade or evaporate.
The tar pits visible today are actually from a human excavation. The lake pit was originally an asphalt mine. The other pits visible today were produced between 1913 and 1915 when over 100 pits were excavated in search of large mammal bones. Various combinations of asphaltum, dust, leaves, and water have since filled in these holes. Normally, the asphalt appears in vents, hardening as it oozes out, to form stubby mounds. These can be seen in several areas of the park.
For hundreds of thousands of years, this seepage has been occurring. For time to time, asphalt formed a crust that was dense enough to trap wildlife, and layers of mud, dust, or leaves would cover the surface. Animals are going to walk in, get stuck and eventually die. Predators would enter and caught to eat the trapped animals. The asphalt soaks inside as the dead animals ‘ bones sink, turning them into a dark-brown or black hue. Lighter fractions of petroleum evaporate from the asphalt, leaving a more solid substance, which encases the bones. Dramatic fossils of large mammals have been extricated from the tar, but the asphalt also preserves microfossils: wood and plant remnants, rodent bones, insects, mollusks, dust, seeds, leaves, and even pollen grains. Examples of some of these are on display in the George C. Page Museum. Radiometric dating of preserved wood and bones has given an age of 38,000 years for the oldest known material from the La Brea seeps. The pits still ensnare organisms today, so most of the pits are fenced to protect humans and animals.
6. Mount St. Helens National Volcanic Monument, Washington
The visitor center near the top of Mount St. Helens is named for David Johnston, the geologist who predicted that the volcano would explode not upward but sideways. Credit: (Steve Terrill / Corbis)
The National Volcanic Monument of Mount St. Helens is a U.S. National Monument, which covers the landscape surrounding Washington’s Mount St. Helens. It was created by the U.S. on August 27, 1982. After the eruption of 1980, President Ronald Reagan. The National Volcanic Monument of 110,000 acres (445 km2) has been set aside for science, tourism and education. The ecosystem within the Monument is left to respond to the disturbance naturally.
Mount St. Helens National Volcanic Monument was the first such monument operated by the United States of America. Service to the wood. Max Peterson, head of the USFS, said at dedication ceremonies on May 18, 1983, “we can be proud to have preserved the special episode of natural history for future generations.” Since then, several trails, viewpoints, information stations, campgrounds and picnic areas have been set up to accommodate the increasing number of visitors every year.
Beginning in 1983, visitors have been able to drive to Windy Ridge, only 4 miles (6.4 km) northeast of the crater.
Mountain climbing to the summit of the volcano has been allowed since 1986.
7. Meteor Crater, Arizona
Meteor Crater in Arizona is 4,000 feet wide and almost 600 feet deep. Credit: (iStockphoto)
The crater was created about 50,000 years ago during the Pleistocene epoch, when the local climate on the Colorado Plateau was much cooler and damper. The area was an open grassland dotted with woodlands inhabited by mammoths and giant ground sloths.
Meteor Crater is about 37 miles (60 km) east of Flagstaff and 18 miles (29 km) west of Winslow in the United States ‘ northern Arizona desert. Since the U.S. Geographic Names Board generally honors names of natural features originating from the nearest post office, the feature obtained the name “Meteor Crater” from the local post office called Meteor. Formerly known as the Canyon Diablo Crater, the site is officially called the Canyon Diablo Meteorite, and parts of the meteorite.
The crater is referred to by scientists as Barringer Crater in honor of Daniel Barringer, who first claimed that it was created by meteorite impact. The crater is owned by the Barringer family privately through its Barringer Crater Company, which claims to be the “best preserved meteorite crater on Earth.” The crater is not protected as a national monument, given its significance as a geological site, a designation that would entail federal ownership. In November 1967, it was designated as a National Natural Landmark.
Meteor Crater is located at an elevation above sea level of 5,640 ft (1,719 m). It is approximately 3,900 ft (1,200 m) in diameter, approximately 560 ft (170 m) deep, and is surrounded by a 148 ft (45 m) rim above the surrounding plains. The crater center is filled with rubble lying above crater bedrock with 690–790 ft (210–240 m). One of the crater’s interesting features is its squared-off outline, which is thought to be caused by existing regional joints (cracks) at the impact site in the strata.
8. Niagara Falls, New York
Niagara Falls, New York
Niagara Falls is a town in the county of Niagara, New York, USA. The city had a total population of 50,193 as of the 2010 census, down from the 55,593 reported in the census of 2000. It is adjacent to the Niagara River, across the Niagara Falls city, Ontario, and named after the famous Niagara Falls that they share. The city is located within the Metropolitan Statistical Area of Buffalo–Niagara Falls and the West New York region.
While the city was formerly occupied by Native Americans, in the mid-17th century, Europeans who migrated to the Niagara Falls began to open businesses and develop infrastructure. Scientists and entrepreneurs later started to harness the power of the Niagara River for electricity in the 18th and 19th centuries, and the city began to attract factories and other companies drawn by the prospect of inexpensive hydroelectric power. Nevertheless, after an attempt at urban renewal under then-Mayor Lackey, the city and region experienced an economic decline after the 1960s. When manufacturing left the city, old line affluent families moved to nearby suburbs and out of town, in line with the rest of the Rust Belt.
Despite the decline in heavy industry, Niagara Falls State Park and the downtown area closest to the falls continue to thrive as a result of tourism. The population, however, has continued to decline from a peak of 102,394 in the 1960s due to the loss of manufacturing jobs in the area.
9. Yellowstone National Park, Idaho, Montana and Wyoming
Yellowstone National Park is an American national park located in Wyoming, Montana, and Idaho.
Yellowstone National Park is an American national park with small sections in Montana and Idaho, mainly located in Wyoming. It was set up by the U.S. Congress and President Ulysses S. Grant signed it into law on March 1, 1872. Yellowstone was the first national park in the U.S. and the first national park in the world is also widely held. The park is known for its wildlife and various geothermal features, including Old Faithful Geyser, one of its most popular features. It has many habitat types, but the most common is the subalpine forest. It is part of the South Central Rockies forests ecoregion.
Native Americans have existed for at least 11,000 years in the Yellowstone area. During the early-to-mid-19th century, apart from visits by mountain men, organized exploration did not begin until the late 1860s. Initially, the management and regulation of the park was under the authority of the Interior Secretary, the first being Columbus Delano. But the U.S. Subsequently, the Army was commissioned to oversee Yellowstone management for a period of 30 years from 1886 to 1916. In 1917, the park administration was moved to the National Park Service established the year before. Hundreds of structures have been built and are protected for their architectural and historical significance, and researchers have examined more than a thousand archaeological sites.
Yellowstone National Park covers an area of 8,983 km2 (3,468.4 square miles), and includes lakes, canyons, rivers and mountain ranges. Yellowstone Lake is one of North America’s largest high-altitude lakes, centered above the Yellowstone Caldera, the continent’s largest supervolcano. The caldera is a volcano that is dormant. Over the past two million years, it has exploded many times with tremendous force. Half of the geysers and hydrothermal properties of the planet are in Yellowstone, caused by this ongoing volcanism. Lava flows and volcanic eruptions rocks cover most of Yellowstone’s land area. The park is at the heart of the Greater Yellowstone Ecosystem, the largest remaining near-intact ecosystem in the northern temperate zone of the Earth. Yellowstone was declared a UNESCO World Heritage Site in 1978.
10. Grand Canyon, Arizona
Grand Canyon, Arizona
The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is 277 miles (446 km) long, up to 18 miles (29 km) wide and attains a depth of over a mile (6,093 feet or 1,857 meters).
Grand Canyon National Park, Kaibab National Forest, Grand Canyon-Parashant National Monument, Hualapai Indian Reservation, Havasupai Indian Reservation, and Navajo Nation contain the canyon and surrounding rim. President Theodore Roosevelt was a major supporter of protecting the Grand Canyon region, visiting it many times to hunt and enjoy the scenery.
Nearly two billion years of the geological history of Earth became uncovered as the Colorado River and its tributaries carved their channels through layer after layer of rock while the Colorado Plateau was elevated. While geologists are discussing some aspects of the canyon’s incision history, several recent studies support the hypothesis that the Colorado River set its course through the area about 5 to 6 million years ago. The Colorado River has since driven down the tributaries and the cliffs ‘ withdrawal, gradually deepening and widening the canyon.
The area has been inhabited continuously by Native Americans for thousands of years, who established villages within the canyon and its numerous caves. The inhabitants of the Pueblo saw the Grand Canyon as a sacred place and made pilgrimages to it. García López de Cárdenas, who arrived in 1540, was the first European known to have seen the Grand Canyon.
The Earth’s inner core is hot, under immense pressure and snow-capped, according to new research that could help scientists better understand forces that affect the entire planet.
The snow is made of tiny particles of iron—much heavier than any snowflake on Earth’s surface—that fall from the molten outer core and pile on top of the inner core, creating piles up to 200 miles thick that cover the inner core.
The image may sound like an alien winter wonderland. But the scientists who led the research said it is akin to how rocks form inside volcanoes.
“The Earth’s metallic core works like a magma chamber that we know better of in the crust,” said Jung-Fu Lin, a professor in the Jackson School of Geosciences at The University of Texas at Austin and a co-author of the study.
The study is available online and will be published in the print edition of the journal JGR Solid Earth on December 23.
Youjun Zhang, an associate professor at Sichuan University in China, led the study. The other co-authors include Jackson School graduate student Peter Nelson; and Nick Dygert, an assistant professor at the University of Tennessee who conducted the research during a postdoctoral fellowship at the Jackson School.
The Earth’s core can’t be sampled, so scientists study it by recording and analyzing signals from seismic waves (a type of energy wave) as they pass through the Earth.
However, aberrations between recent seismic wave data and the values that would be expected based on the current model of the Earth’s core have raised questions. The waves move more slowly than expected as they passed through the base of the outer core, and they move faster than expected when moving through the eastern hemisphere of the top inner core.
The study proposes the iron snow-capped core as an explanation for these aberrations. The scientist S.I. Braginkskii proposed in the early 1960s that a slurry layer exists between the inner and outer core, but prevailing knowledge about heat and pressure conditions in the core environment quashed that theory. However, new data from experiments on core-like materials conducted by Zhang and pulled from more recent scientific literature found that crystallization was possible and that about 15% of the lowermost outer core could be made of iron-based crystals that eventually fall down the liquid outer core and settle on top of the solid inner core.
“It’s sort of a bizarre thing to think about,” Dygert said. “You have crystals within the outer core snowing down onto the inner core over a distance of several hundred kilometers.”
The researchers point to the accumulated snow pack as the cause of the seismic aberrations. The slurry-like composition slows the seismic waves. The variation in snow pile size—thinner in the eastern hemisphere and thicker in the western—explains the change in speed.
“The inner-core boundary is not a simple and smooth surface, which may affect the thermal conduction and the convections of the core,” Zhang said.
The paper compares the snowing of iron particles with a process that happens inside magma chambers closer to the Earth’s surface, which involves minerals crystalizing out of the melt and glomming together. In magma chambers, the compaction of the minerals creates what’s known as “cumulate rock.” In the Earth’s core, the compaction of the iron contributes to the growth of the inner core and shrinking of the outer core.
And given the core’s influence over phenomena that affects the entire planet, from generating its magnetic field to radiating the heat that drives the movement of tectonic plates, understanding more about its composition and behavior could help in understanding how these larger processes work.
Bruce Buffet, a geosciences professor at the University of California, Berkley who studies planet interiors and who was not involved in the study, said that the research confronts longstanding questions about the Earth’s interior and could even help reveal more about how the Earth’s core came to be.
“Relating the model predictions to the anomalous observations allows us to draw inferences about the possible compositions of the liquid core and maybe connect this information to the conditions that prevailed at the time the planet was formed,” he said. “The starting condition is an important factor in Earth becoming the planet we know.”
Reference:
Youjun Zhang et al, Fe Alloy Slurry and a Compacting Cumulate Pile Across Earth’s Inner‐Core Boundary, Journal of Geophysical Research: Solid Earth (2019). DOI: 10.1029/2019JB017792
Whakaari/White Island, New Zealand. On December 9, 2019, several Australians were among the dozens of tourists who were killed, injured, or went missing when the volcano erupted. Credit: Rfleming/public domain.
Heather Handley pointed out two large photos on her poster at AGU Fall Meeting last week: a bouncing kangaroo and a dreamy beach scene, two things commonly associated with Australia, where Handley is an associate professor in volcanology at Macquarie University. But Handley wasn’t advertising Australia’s most loved assets. The photos were a lead up to an introduction of one of her country’s lesser known features: volcanoes.
On December 9, several Australians were among the dozens of tourists who were killed, injured, or went missing after a deadly eruption on Whakaari/White Island in New Zealand. Whakaari/White Island has seen more volcanic activity in the past 10 years than neighboring Australia has seen for 5,000, but according to volcanologists like Handley, the country is not free from the risks of a potential eruption. And according to a new survey conducted by Handley and her colleagues, Australian citizens are mostly unaware of their country’s potential volcanic hazards.
Handley and colleagues came up with a series of questions for a survey, sent out just last month through social media and flyers, to find out just how much Australians understand the volcanic hazards and risk in their homeland.
At Fall Meeting, Handley presented the preliminary results from survey responses of over 100 Australians. She found that over 90 percent of respondents are unaware of any preparedness, emergency management plans, or warning systems in Australia for volcanic hazards.
Over 25 percent of survey takers said they weren’t sure when the last volcanic eruption in mainland Australia occurred (Mt. Gambier, around 5,000 years ago). Additionally, for the statement “I am well aware of the procedures I need to follow in the event of an emergency related to a volcanic eruption,” over 70 percent disagreed, and 60 percent strongly disagreed.
The survey participants did, however, seem to know that Australia could be impacted by volcanic activity in other countries, with nearly 80 percent agreeing with the statement.
A 2011 eruption in Chile may be partially responsible for this awareness, Handley said. Volcanic ash produced by that eruption entered Australian airspace, grounding planes and affecting over 100,000 passengers. Australia is also surrounded by several volcanically active countries: New Zealand, Indonesia, Papua New Guinea, and Tonga.
A more surprising result for Handley came from the question regarding various levels of concern for natural hazards in their country. For volcanic hazards, about 65 percent of people answered “not at all concerned” and zero people responded “extremely concerned.”
In the same way the Chile eruption could have contributed to recent understanding of how volcanoes in other countries could impact Australia, Handley attributes the lack of concern for local volcanoes to timescales: the last eruption on the mainland occurred before Europeans colonized Australia.
But indigenous populations occupied Australia for around 65,000 years before European colonizers arrived, and they were aware of the volcanic hazards. “They did witness eruptions, and they did pass on that knowledge through oral traditions,” Handley said. She’s also looking at combining scientific data with indigenous knowledge to better improve scientists’ understanding of volcanic activity in Australia.
Handley is just at the start of her surveying and anticipates a shift in future survey responses after the recent eruption on Whakaari/White Island. “It’s probably triggering a few people to think about Australia—what is the risk to us from an eruption that might not be easy to predict,” she said.
Handley studies the Newer Volcanics Province, a 400-kilometer swath of land stretching from Melbourne to South Australia, home to more than 400 small, previously active volcanoes. Predicting another eruption across such a wide area is tricky, because an eruption could happen anywhere, she said. Handley suspects the Newer Volcanics Province could see another eruption, based on chemical and geophysical signals pointing to magma in Earth’s mantle beneath the Province.
Handley is also studying how quickly magma travels, which may help predict warning times if volcanic activity starts to increase. But prediction won’t matter much if the public isn’t aware of the risk, or if there is no plan in place in the case of an event in the Newer Volcanics Province, she said.
Handley hopes her research will help emergency management officials create tools and literature related to volcanic hazards preparedness.
Artist’s depiction of an ornithopod dinosaur tending its nest. Credit: University of New England
Researchers have uncovered the first baby dinosaurs from Australia. The bones were discovered at several sites along the south coast of Victoria and near the outback town of Lightning Ridge in New South Wales. Some of the bones are so tiny, they likely come from animals that had died while they were still in their eggs. Slightly larger bones from Victoria come from animals that had recently hatched but were probably nest-bound.
The research was carried out by palaeontologists from the Palaeoscience Research Centre at the University of New England and the Australian Opal Centre in Lightning Ridge.
The bones come from small-bodied ornithopod dinosaurs—two legged herbivores that weighed roughly 20kg when full grown—similar to Weewarrasaurus, which was recently discovered by members of the same team at Lightning Ridge. By comparison, the baby dinosaurs were only about 200g when they died, less that the weight of a cup of water.
While the eggs themselves were not found, researchers used growth rings in the bones, similar to the rings in a tree trunk, to estimate the animal’s age. “Age is usually estimated by counting growth rings, but we couldn’t do this with our two smallest specimens, which had lost their internal detail,” says Justin Kitchener, a Ph.D. student at the University of New England, who also led the study. “To get around this, we compared the size of these bones with the size of growth rings from the Victorian dinosaurs. This comparison confidently places them at an early growth stage, probably prior to, or around the point of hatching.”
100 million years ago, when these animals were being born, Australia was much closer to the poles. Southeastern Australia would have been between 60°S and 70°S, equivalent to modern day Greenland. Although the climate at these latitudes was relatively warmer than they are today, like some Antarctic penguins, these dinosaurs would have endured long dark winters and possibly burrowed or hibernated to survive.
Because they are so delicate, egg shell and tiny bones rarely survive to become fossils. “We have examples of hatchling-sized dinosaurs from close to the North Pole, but this is the first time we’ve seen this kind of thing anywhere in the Southern Hemisphere,” says Dr. Phil Bell, a University of New England palaeontologist who recognised the significance of the tiny bones from Lightning Ridge. “It’s the first clue we’ve had about where these animals were breeding and raising their young.”
The study was published today in the journal Scientific Reports.
Representative Image : The Earth’s layers, showing the Inner and Outer Core, the Mantle, and Crust
New research from Mauricio Ibanez-Mejia, an assistant professor of Earth and environmental sciences at the University of Rochester, gives scientists better insight into the geological processes responsible for the formation of Earth’s crust.
In a paper published in the journal Science Advances, Ibanez-Mejia and his colleague Francois Tissot, an assistant professor of geochemistry at the California Institute of Technology, studied the isotopes of the element zirconium.
Most elements in the periodic table have multiple isotopes; that is, different atoms of the same element can have different masses due to the varying number of sub-atomic particles in their nuclei. Researchers have traditionally assumed that processes occurring within the solid Earth, particularly in high-temperature environments such as those found in volcanoes and magma chambers, do not have the ability to ‘fractionate’—distribute unevenly—isotopes of the heavy elements amongst solids and liquids because of the isotopes’ minute differences in mass.
In the study, the researchers showed that stable isotopes of the element zirconium, a heavy transition metal, can be fractionated by magnitudes much larger than those previously thought and predicted by theory.
“This changes our view of how this element behaves in the solid Earth,” Ibanez-Mejia says. “By recognizing this variability, we developed a tool that can help us gain further insights into the changing chemistry of magmas as they crystallize within Earth’s crust.”
Reference:
Mauricio Ibañez-Mejia et al, Extreme Zr stable isotope fractionation during magmatic fractional crystallization, Science Advances (2019). DOI: 10.1126/sciadv.aax8648
A schematic summary of the effect of the convergence rate. Upper image shows a slow convergence rate allows thermal difussion and a derived reduction of slab’s density (positive buoyancy). Lower image shows how a faster convergence rate increases the slab’s density promoting the negative buoyancy. Credit: Kittiphon Boonma, Scientific Reports
A fast collision rate between tectonic plates and a young age (millions of years) are two factors that favour the sinking of the lithosphere in the mantle, according to a new study made by researchers at the Institute of Earth Sciences Jaume Almera of the Spanish National Research Council (ICTJA-CSIC). The study has been published recently in Scientific Reports.
The authors of the study developed a new numerical model to study the effects of the convergence rate between tectonic plates and its composition on the lithospheric mantle density promoting or avoiding its sinking during subduction or delaminating processes.
“The model designed in this study provides a methodological framework for understanding the stability of the lithosphere during the convergence of the tectonic plates,” said Kittiphon Boonma, Ph.D. student of the SUBITOP project at ICTJA-CSIC and first author of the study.
The lithosphere is the Earth’s rigid outermost layer that comprises the crust and uppermost mantle, forming the tectonic plates. These plates float and move over the asthenosphere, a denser and more viscous layer of the sublithospheric mantle. In the areas where plates converge, one of the plates sinks below the other, thrusting into the sublithospheric mantle. This would be the typical case of the oceanic lithosphere subduction zones. Another possibility is that, in continental collision zones, the lithospheric mantle of one of the plates separates from (“peels off”) the crust and sinks into the asthenosphere in a process known as delamination. Both processes are sensitive to the lithospheric mantle density which, at the same time, depends on the pressure, temperature and chemical composition or, which is the same, of the convergence rate and the age of the lithosphere.
“Our simulations combine lithospheric composition for different plate ages with a wide spectrum of plate collision rates to understand what determines the positive or negative buoyancy of the lithosphere,” said Daniel García-Castellanos, researcher at ICTJA-CSIC and co-author of the study.
“The main advance of our work is the analysis of the dependence of lithospheric mantle buoyancy on density variations resulting from the advection-diffusion balance considering a wide range of tectonic convergence rates and different lithospheric mantle chemical compositions,” said Kittiphon Boonma.
Researchers performed several simulations with the new model considering three different types of continental lithosphere, with an age range between 2.5 Ga and 1 Ga year, and two oceanic lithospheres aged 120 and 30 milion year old. They considered six different convergence rates between 1 and 80 mm/year. Simulations were aimed to observe the effect of the different collision rates and compositions on the lithospheric mantle density.
“In subduction or continental collision processes, there are two opposite effects that affect the mantle density. Density increases due to pressure increases but, at the same time, it tends to decrease due to the temperature increase produced by the depth. The predominance of one of these two effects will depend on the convergence velocity. Moreover, the mantle density depends also on its own chemical composition and it has been observed that it decreases with the age,” explains Manel Fernández, co-author of the study.
The model outcomes showed that the oldest and thickest continental lithospheric mantle (Archon) was less dense than the asthenosphere and avoided the sinking. At low and moderate convergence rates, researchers found that the two other types of continental lithospheric mantle shifted from sinking to stay stables due to their thinner thicknesses and to the loss of density induced by the temperature increases due to the depth. Last, the two different types oceanic lithosphere always sank, whatever the applied convergence rate was, due to their bigger density derived from it composition.
“According to these results, the faster the convergence rate between two continents, the bigger the probability that one of them delaminates or sinks towards the mantle,” explains Daniel García-Castellanos.
“Results suggest an explanation on why the young plates often sinks easily into the mantle, being recycled in the mantle while cratons (oldest continental regions) seem to resist better the changes in tectonic forces during Earth’s evolution and they are less prone to subduct or delaminate,” said García-Castellanos.
Reference:
K. Boonma et al. Lithospheric mantle buoyancy: the role of tectonic convergence and mantle composition, Scientific Reports (2019). DOI: 10.1038/s41598-019-54374-w
The specimen will be stripped of the scientific name Mongolarachne chaoyangensis and rechristened as a crayfish. Credit: Selden et al.
Earlier this year, a remarkable new fossil specimen was unearthed in the Lower Cretaceous Yixian Formation of China by area fossil hunters — possibly a huge ancient spider species, as yet unknown to science.
The locals sold the fossil to scientists at the Dalian Natural History Museum in Liaoning, China, who published a description of the fossil species in Acta Geologica Sinica, the peer-reviewed journal of the Geological Society of China. The Chinese team gave the spider the scientific name Mongolarachne chaoyangensis.
But other scientists in Beijing, upon seeing the paper, had suspicions. The spider fossil was huge and strange looking. Concerned, they contacted a U.S. colleague who specializes in ancient spider fossils: Paul Selden, distinguished professor of invertebrate paleontology in the Department of Geology at the University of Kansas.
“I was obviously very skeptical,” Selden said. “The paper had very few details, so my colleagues in Beijing borrowed the specimen from the people in the Southern University, and I got to look at it. Immediately, I realized there was something wrong with it — it clearly wasn’t a spider. It was missing various parts, had too many segments in its six legs, and huge eyes. I puzzled and puzzled over it until my colleague in Beijing, Chungkun Shih, said, ‘Well, you know, there’s quite a lot of crayfish in this particular locality. Maybe it’s one of those.’ So, I realized what happened was I got a very badly preserved crayfish onto which someone had painted on some legs.”
Selden and his colleagues at KU and in China (including the lead author of the paper originally describing the fossil) recently published an account of their detective work in the peer-reviewed journal Palaeoentomology.
“These things are dug up by local farmers mostly, and they see what money they can get for them,” Selden said. “They obviously picked up this thing and thought, ‘Well, you know, it looks a bit like a spider.’ And so, they thought they’d paint on some legs — but it’s done rather skillfully. So, at first glance, or from a distance, it looks pretty good. It’s not till you get down to the microscope and look in detail that you realize they’re clearly things wrong with it. And, of course, the people who described it are perfectly good paleontologists — they’re just not experts on spiders. So, they were taken in.”
In possession of the original fossil specimen at KU, Selden teamed up with his graduate student Matt Downen and with Alison Olcott, associate professor of geology. The team used fluorescence microscopy to analyze the supposed spider and differentiate what parts of the specimen were fossilized organism, and which parts were potentially doctored.
“Fluorescence microscopy is a nice way of distinguishing what’s painted on from what’s real,” Selden said. “So, we put it under the fluorescence microscope and, of course, being a huge specimen it’s far too big for the microscope. We had to do it in bits. But we were able to show the bits that were painted and distinguish those from the rock and from the actual, real fossil.”
The team’s application of fluorescence microscopy on the fossil specimen showed four distinct responses: regions that appear bright white, bright blue, bright yellow, and ones that are dull red. According to the paper, the bright white areas are probably a mended crack. The bright blue is likely from mineral composition of the host rock. The yellow fluorescence could indicate an aliphatic carbon from oil-based paint used to alter the crayfish fossil. Finally, the red fluorescence probably indicates the remnants of the original crayfish exoskeleton.
“We produced this little paper showing how people could be very good at faking what was clearly a rather poor fossil — it wasn’t going to bring in a lot of money — and turning it into something which somebody bought for quite a lot of money, I imagine, but it clearly was a fake,” the KU researcher said.
Selden said in the world of fossils fakery is commonplace, as impoverished fossil hunters are apt to doctor fossils for monetary gain.
What’s less common, he said, was a fake fossil spider, or a forgery making its way into an academic journal. However, he acknowledged the difficulty of verifying a fossil and admitted he’d been fooled in the past.
“I mean, I’ve seen lots of forgeries, and in fact I’ve even been taken in by fossils in a very dark room in Brazil,” he said. “It looked interesting until you get to in the daylight the next day realize it’s been it’s been enhanced, let’s say, for sale. I have not seen it with Chinese invertebrates before. It’s very common with, you know, really expensive dinosaurs and that sort of stuff. Maybe they get two fossils and join them together, this kind of thing. Normally, there’s not enough to gain from that kind of trouble with an invertebrate.
“But somebody obviously thought it wasn’t such a big deal to stick a few legs onto this, because a giant spider looks very nice. I’m not sure the people who sell them necessarily think they’re trying to dupe scientists. You tend to come across these things framed — they look very pretty. They’re not necessarily going to be bought by scientists, but by tourists.”
Selden’s coauthors on the paper were Olcott and Downen of KU, along with Shih of Capital Normal University in Beijing, and Dong Ren of Capital Normal University and the Smithsonian Institution, and Ciaodong Cheng of Dalian Natural History Museum.
Selden didn’t know the eventual fate of the enhanced spider fossil, which he likened to the famed “jackalope.”
He said he thought it would go back to China where it could be put on display as a cautionary tale. One thing is for certain: it will be stripped of the scientific name Mongolarachne chaoyangensis and rechristened as a crayfish. Because of the fossil’s alterations and state of preservation, Selden said it was hard to pin down its exact species. The team tentatively placed the fossil in Cricoidoscelosus aethus, “because this is marginally the commoner of the two crayfish recorded from the Yixian Formation.”
Wood opal is a form of petrified wood which has developed an opalescent sheen or, more rarely, where the wood has been completely replaced by opal. Other names for this opalized sheen-like wood are opalized wood and opalized petrified wood. It is often used as a gemstone.
How Does Opalized Wood Form?
Due to a series of rhyolite volcanic flows, resulting in a large basin enclosed by low hills. This basin contained a succession of lakes and forests of spruce, hemlock, birch, chestnut and even sequoia which were periodically buried by volcanic ash hundreds of feet thick. A large lake formed within the basin which deposited large amounts of diatomite, a biogenic form of silica. Seepage of super-heated water percolated through the ash layers, carrying silica to the long-buried trees.
Replacement of carbon in the wood by hydrated silica resulted in perfect opalized replicas of the original wood structure. It is the alignment of the hydrated silica spheres which ultimately results in the rainbow effect of precious opal, the result of deflection and diffraction of light as it passes through the planes of hydrated silica molecules. The size of the spheres impacts the colors seen, with smaller spheres resulting in blues and larger spheres in reds. While common opal is abundant in the region, the conditions required for formation of precious opal as seen here was far more rare, a combination of a stable and undisturbed environment. While much of the world precious opal is found in Austarlia, deposits such as those in the Virgin Valley are also mined for these treasures of a bygone world.
How Does Petrified Wood Form?
As the internal structure of our plant gradually breaks down, it replaces its organic material (wood fibers) with silica and other minerals. Those minerals will crystallize over a period of a few million years. The end result is a rock that takes over our original tree’s shape and structure.
The petrifaction process occurs underground, when wood becomes buried in water saturated sediment or volcanic ash. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to permineralization, which occurs when minerals precipitate out of solution filling the interiors of cells and other empty spaces. During replacement, the plant’s cell walls act as a template for mineralization.
There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. Most of the organic matter often decomposes, however some of the lignin may remain. Silica in the form of Opal-A, can encrust and permeate wood relatively quickly in hot spring environments. However, petrified wood is most commonly associated with trees that were buried in fine grained sediments of deltas and floodplains or volcanic lahars and ash beds. A forest where such material has petrified becomes known as a petrified forest.
Is petrified wood valuable?
“Small pieces of petrified wood are quite common and not worth very much.
A fossilized snail shell, ready to be analyzed in the laboratory. Credit: Northwestern University
New evidence gleaned from Antarctic seashells confirms that Earth was already unstable before the asteroid impact that wiped out the dinosaurs.
The study, led by researchers at Northwestern University, is the first to measure the calcium isotope composition of fossilized clam and snail shells, which date back to the Cretaceous-Paleogene mass extinction event. The researchers found that — in the run-up to the extinction event — the shells’ chemistry shifted in response to a surge of carbon in the oceans.
This carbon influx was likely due to long-term eruptions from the Deccan Traps, a 200,000-square-mile volcanic province located in modern India. During the years leading up to the asteroid impact, the Deccan Traps spewed massive amounts of carbon dioxide (CO2) into the atmosphere. The concentration of CO2 acidified the oceans, directly affecting the organisms living there.
“Our data suggest that the environment was changing before the asteroid impact,” said Benjamin Linzmeier, the study’s first author. “Those changes appear to correlate with the eruption of the Deccan Traps.”
“The Earth was clearly under stress before the major mass extinction event,” said Andrew D. Jacobson, a senior author of the paper. “The asteroid impact coincides with pre-existing carbon cycle instability. But that doesn’t mean we have answers to what actually caused the extinction.”
The study will be published in the January 2020 issue of the journal Geology, which comes out later this month.
Jacobson is a professor of Earth and planetary sciences in Northwestern’s Weinberg College of Arts and Sciences. Linzmeier was a postdoctoral researcher with the Ubben Program for Climate and Carbon Science at the Institute for Sustainability and Energy at Northwestern when the research was conducted. He is now a postdoctoral fellow at the University of Wisconsin-Madison in the Department of Geoscience.
‘Each shell is a snapshot’
Previous studies have explored the potential effects of the Deccan Traps eruptions on the mass extinction event, but many have examined bulk sediments and used different chemical tracers. By focusing on a specific organism, the researchers gained a more precise, higher-resolution record of the ocean’s chemistry.
“Shells grow quickly and change with water chemistry,” Linzmeier said. “Because they live for such a short period of time, each shell is a short, preserved snapshot of the ocean’s chemistry.”
Seashells mostly are composed of calcium carbonate, the same mineral found in chalk, limestone and some antacid tablets. Carbon dioxide in water dissolves calcium carbonate. During the formation of the shells, CO2 likely affects shell composition even without dissolving them.
For this study, the researchers examined shells collected from the Lopez de Bertodano Formation, a well-preserved, fossil-rich area on the west side of Seymour Island in Antarctica. They analyzed the shells’ calcium isotope compositions using a state-of-the-art technique developed in Jacobson’s laboratory at Northwestern. The method involves dissolving shell samples to separate calcium from various other elements, followed by analysis with a mass spectrometer.
“We can measure calcium isotope variations with high precision,” Jacobson said. “And those isotope variations are like fingerprints to help us understand what happened.”
Using this method, the team found surprising information.
“We expected to see some changes in the shells’ composition, but we were surprised by how quickly the changes occurred,” Linzmeier said. “We also were surprised that we didn’t see more change associated with the extinction horizon itself.”
A future warning
The researchers said that understanding how the Earth responded to past extreme warming and CO2 input can help us prepare for how the planet will respond to current, human-caused climate change.
“To some degree, we think that ancient ocean acidification events are good analogs for what’s happening now with anthropogenic CO2 emissions,” Jacobson said. “Perhaps we can use this work as a tool to better predict what might happen in the future. We can’t ignore the rock record. The Earth system is sensitive to large and rapid additions of CO2. Current emissions will have environmental consequences.”
Brad Sageman and Matthew Hurtgen, both professors of Earth and planetary sciences at Northwestern, are co-senior authors of the paper.
The study, “Calcium isotope evidence for environmental variability before and across the Cretaceous-Paleogene mass extinction,” was supported by the Ubben Program for Climate and Carbon Science at Northwestern University, the David and Lucile Packard Foundation (award number 2007-31757) and the National Science Foundation (award numbers EAR-0723151, ANT-1341729, ANT-0739541 and ANT-0739432.
Reference:
Benjamin J. Linzmeier, Andrew D. Jacobson, Bradley B. Sageman, Matthew T. Hurtgen, Meagan E. Ankney, Sierra V. Petersen, Thomas S. Tobin, Gabriella D. Kitch, Jiuyuan Wang. Calcium isotope evidence for environmental variability before and across the Cretaceous-Paleogene mass extinction. Geology, 2019; DOI: 10.1130/G46431.1
Rocks containing microscopic fossil pollen were collected to determine the age of fossil leaves from Castle Cove, Otway Ranges, Victoria. Credit: Vera Korasidis
New research has revealed that Australia’s oldest flowering plants are 126 million years old and may have resembled modern magnolias, buttercups and laurels.
Undertaken by University of Melbourne palynologist, Dr Vera Korasidis, the study also found that Australia’s first blooms got their foothold in ‘high southern latitude’ regions like the Otway and Gippsland ranges.
Dr Korasidis’ research, “The rise of flowering plants in the high southern latitudes of Australia,” reconstructed our earliest flower-bearing forests, from 126-100 million years ago, to conclude that climate change prevented or slowed the expansion of flowers into Australasia with the temperatures at the high southern latitudes too cold to support the earliest flowering plants.
The research also established that the first flowers related to 72 per cent of today’s living angiosperm species that first appeared in southern Australia about 108 million years ago — 17 million years after the first flowers evolved in equatorial regions.
The world’s oldest flower, Montsechia, is 130 million years old and was discovered in Spain.
“Our research, completed on dinosaur-bearing rocks throughout Victoria,suggests that warming temperatures allowed the first flowering plants to migrate to the cooler regions at the earth’s poles,” said Dr Korasidis.
“The true diversity of primitive flowers in southern near-polar settings has only just been discovered because ‘sieving’ practices resulted in pollen grains, produced by the earlier flowers, being ‘rinsed down the sink’ for over 50 years.”
Dr Korasidis said the study would help to “piece together Australia’s paleoclimate record and understand the interaction between climate, CO2 and the evolution of faunas and floras.”
The age of southern Australia’s polar vertebrates, including dinosaurs, has also now been determined and is 126-110 million years old based on this study and new research by fellow University of Melbourne palynologist and co-author, Dr Barbara Wagstaff.
Angiosperm pollen produced by the oldest flowers was recovered from numerous sites across Victoria indicating the large areal extent of flowers during the Early Cretaceous period. All material is housed in the Palaeontology collection at Museum Victoria in Melbourne.
Reference:
Vera A. Korasidis, Barbara E. Wagstaff. The rise of flowering plants in the high southern latitudes of Australia. Review of Palaeobotany and Palynology, 2020; 272: 104126 DOI: 10.1016/j.revpalbo.2019.104126
An intimidating sight: Asfaltovenator vialidadi. Source: Gabriel Lio
A new find from Patagonia sheds light on the evolution of large predatory dinosaurs. Features of the 8-meter-long specimen from the Middle Jurassic suggest that it records a phase of rapid diversification and evolutionary experimentation.
In life, it must have been an intimidating sight. The dimensions of the newly discovered dinosaur fossil suggest that this individual was up to 8 meters long, and its skull alone measured 80 centimeters from front to back. The specimen was uncovered by the Munich paleontologist Oliver Rauhut in Patagonia, and can be assigned to the tetanurans—the most prominent group of bipedal dinosaurs, which includes such iconic representatives as Allosaurus, Tyrannosaurus and Velociraptor. This is also the group from which modern birds are derived. The new find is the most complete dinosaur skeleton yet discovered from the early phase of the Middle Jurassic, and is between 174 and 168 million years old. The specimen represents a previously unknown genus, and Rauhut and his Argentinian colleague Diego Pol have named it Asfaltovenator vialidadi. The genus name includes both Greek and Latin components (including the Latin term for hunter), while also referring to the nature of the deposits in which the fossil was found and the species name honours the road maintance of Chubut, who helped in the recovery of the specimen.
Almost the entire skull is preserved, together with the complete vertebral column including parts of the pelvis, all the bones of both anterior extremities and parts of the legs. “The fossil displays a very unusual combination of skeletal characters, which is difficult to reconcile with the currently accepted picture of the relationships between the three large groups that comprise the tetanurans—Megalosauria, Allosauria and Coelurosauria,” says Rauhut, who is Professor of Palaeontology in the Department of Earth and Environmental Sciences at LMU and Senior Curator of the Bavarian State Collection for Paleontology and Geology. He and his co-author Diego Pol, who is based in the Museo Paleontológico Egidio Feruglio in Trelew (Argentina), describe the find in a paper that appears in the online journal Scientific Reports. According to the authors, A. vialidadi exhibits a diverse set of skeletal traits, which combines characters that have so far been found to be specific for various other species of dinosaurs.
The unusual mixture of morphological features displayed by A. vialidadi prompted the authors to carry out a comparative analysis with other tetanurans. They noted that around the period to which the new find can be assigned, the geographical range of this group was rapidly expanding, while the different species developed very similar sets of skeletal features.
Rauhut links the explosive evolution of the group with an episode of mass extinction that had occurred in the late stage of the Lower Jurassic, about 180 million years ago. The two researchers therefore interpret the parallel development of similar external traits in different species as an example of evolutionary experimentation during the subsequent rapid expansion and diversification of the tetanurans. The prior extinction of potential competitors will have opened up new ecological niches for the groups that survived, and the tetanurans were apparently among those that benefited.
“This is a pattern that we also observe in many other groups of animals in the aftermath of mass extinctions. It holds, for example, for the expansion and diversification of both mammals and birds following the extinction of the dinosaurs at the end of the Cretaceous 66 million years ago,” says Rauhut. It could also explain why it is so difficult to unravel the phylogenetic relationships close to the origin of many highly diversified animal groups.
Reference:
Oliver W. M. Rauhut et al. Probable basal allosauroid from the early Middle Jurassic Cañadón Asfalto Formation of Argentina highlights phylogenetic uncertainty in tetanuran theropod dinosaurs, Scientific Reports (2019). DOI: 10.1038/s41598-019-53672-7
The Great Escarpment in Karoo National Park, South Africa, looking across the Lower Karoo. Credit: Wikimedia Commons
Some 250 million years ago, simultaneous mass extinctions of marine and terrestrial life occurred in an event known as the End-Permian. Or so scientists believed.
New research led by Colby College geologist Robert Gastaldo has revealed the most definitive proof to date that the extinctions did not occur at the same time. The findings, published in the journal PALAIOS, have implications for the impact of a possible future biodiversity crisis driven by climate change and a warming planet.
The NSF-funded research shows that the vertebrate fossil record reported in earlier studies—which has been used as the standard in interpreting Earth’s largest known mass extinction—is inaccurate and not sufficient to substantiate the long-held belief that marine species and terrestrial vertebrates perished together.
The findings, which resulted from 15 years of research in South Africa’s Karoo Basin, show that an event 250 million years ago devastated marine life but didn’t affect life on land. Terrestrial change happened hundreds of thousands of years earlier and very gradually, the scientists found.
“While the initial goal was to corroborate conclusions of earlier studies about what is known as the End-Permian event, our data have consistently been at odds with what has been reported,” said Gastaldo. “Purportedly extinct creatures were actually roaming around the Karoo hundreds of thousands of years later than the time scientists had written them off. And their successors were alive before they were supposed to have evolved.”
Gastaldo and colleagues came to these conclusions after examining the placement of fossil remains in the rock layers of the Karoo Basin.
“This study provides a new perspective on the largest mass extinction event in Earth’s history,” said Dena Smith, a program director in NSF’s Division of Earth Sciences. “Studies like this help us learn about past events, and can help us understand the potential effects of modern climate shifts.”
