back to top
27.8 C
New York
Saturday, November 16, 2024
Home Blog Page 273

New view of Mount Rainier’s volcanic plumbing

This image was made by measuring how the ground conducts or resists electricity in a study co-authored by geophysicist Phil Wannamaker of the University of Utah Energy & Geoscience Institute. It shows the underground plumbing system that provides molten and partly molten rock to the magma chamber beneath the Mount Rainier volcano in Washington state. The scale at left is miles depth. The scale at bottom is miles from the Pacific Coast. The Juan de Fuca plate of Earth’s Pacific seafloor crust and upper mantle is shown in blue on the left half of the image as it dives or ‘subducts’ eastward beneath Washington state. The reddish orange and yellow colors represent molten and partly molten rock forming atop the Juan de Fuca plate or ‘slab.’ The image shows the rock begins to melt about 50 miles beneath Mount Rainier (the red triangle at top). Some is pulled downward and eastward as the slab keeps diving, but other melts move upward to the orange magma chamber shown under but west of Mount Rainier. The line of sensors used to make this image were placed north of the 14,410-foot peak, so the image may be showing a lobe of the magma chamber that extends northwest of the mountain. Red ovals on the left half of the page are the hypocenters of earthquakes. Credit: R Shane McGary, Woods Hole Oceanographic Institution.

By measuring how fast Earth conducts electricity and seismic waves, a University of Utah researcher and colleagues made a detailed picture of Mount Rainier’s deep volcanic plumbing and partly molten rock that will erupt again someday.
“This is the most direct image yet capturing the melting process that feeds magma into a crustal reservoir that eventually is tapped for eruptions,” says geophysicist Phil Wannamaker, of the university’s Energy & Geoscience Institute and Department of Civil and Environmental Engineering. “But it does not provide any information on the timing of future eruptions from Mount Rainier or other Cascade Range volcanoes.”

The study was published today in the journal Nature by Wannamaker and geophysicists from the Woods Hole Oceanographic Institution in Massachusetts, the College of New Jersey and the University of Bergen, Norway.

In an odd twist, the image appears to show that at least part of Mount Rainier’s partly molten magma reservoir is located about 6 to 10 miles northwest of the 14,410-foot volcano, which is 30 to 45 miles southeast of the Seattle-Tacoma area.

But that could be because the 80 electrical sensors used for the experiment were placed in a 190-mile-long, west-to-east line about 12 miles north of Rainier. So the main part of the magma chamber could be directly under the peak, but with a lobe extending northwest under the line of detectors, Wannamaker says.

The top of the magma reservoir in the image is 5 miles underground and “appears to be 5 to 10 miles thick, and 5 to 10 miles wide in east-west extent,” he says. “We can’t really describe the north-south extent because it’s a slice view.”

Wannamaker estimates the reservoir is roughly 30 percent molten. Magma chambers are like a sponge of hot, soft rock containing pockets of molten rock.

The new image doesn’t reveal the plumbing tying Mount Rainier to the magma chamber 5 miles below it. Instead, it shows water and partly molten and molten rock are generated 50 miles underground where one of Earth’s seafloor crustal plates or slabs is “subducting” or diving eastward and downward beneath the North America plate, and how and where those melts rise to Rainier’s magma chamber.

The study was funded largely by the National Science Foundation’s Earthscope program, which also has made underground images of the United States using seismic or sound-wave tomography, much like CT scans show the body’s interior using X-rays.

The new study used both seismic imaging and magnetotelluric measurements, which make images by showing how electrical and magnetic fields in the ground vary due to differences in how much underground rock and fluids conduct or resist electricity.

Wannamaker says it is the most detailed cross-section view yet under a Cascades volcanic system using electrical and seismic imaging. Earlier seismic images indicated water and partly molten rock atop the diving slab. The new image shows melting “from the surface of the slab to the upper crust, where partly molten magma accumulates before erupting,” he adds.

Wannamaker and Rob L. Evans, of the Woods Hole Oceanographic Institution, conceived the study. First author R Shane McGary — then at Woods Hole and now at the College of New Jersey — did the data analysis. Other co-authors were Jimmy Elsenbeck of Woods Hole and Stéphane Rondenay of the University of Bergen.

Mount Rainier: Hazardous Backdrop to Metropolitan Seattle-Tacoma

Mount Rainier, the tallest peak in the Cascades, “is an active volcano that will erupt again,” says the U.S. Geological Survey. Rainier sits atop volcanic flows up to 36 million years old. An ancestral Rainier existed 2 million to 1 million years ago. Frequent eruptions built the mountain’s modern edifice during the past 500,000 years. During the past 11,000 years, Rainier erupted explosively dozens of times, spewing ash and pumice.

Rainier once was taller until it collapsed during an eruption 5,600 years ago to form a large crater open to the northeast, much like the crater formed by Mount St. Helens’ 1980 eruption. The 5,600-year-old eruption sent a huge mudflow west to Puget Sound, covering parts or all of the present sites of the Port of Tacoma, Seattle suburbs Kent and Auburn, and the towns Puyallup, Orting, Buckley, Sumner and Enumclaw.

Rainier’s last lava flows were 2,200 years ago, the last flows of hot rock and ash were 1,100 years ago and the last big mudflow 500 years ago. There are disputed reports of steam eruptions in the 1800s.

Subduction Made Simple — and a Peek beneath a Peak

The “ring of fire” is a zone of active volcanoes and frequent earthquake activity surrounding the Pacific Ocean. It exists where Earth’s tectonic plates collide — specifically, plates that make up the seafloor converge with plates that carry continents.

From Cape Mendocino in northern California and north past Oregon, Washington state and into British Columbia, an oceanic plate is being pushed eastward and downward — a process called subduction — beneath the North American plate. This relatively small Juan de Fuca plate is located between the huge Pacific plate and the Pacific Northwest.

New seafloor rock — rich with water in cracks and minerals — emerges from an undersea volcanic ridge some 250 miles off the coast, from northern California into British Columbia. That seafloor adds to the western edge of the Juan de Fuca plate and pushes it east-northeast under the Pacific Northwest, as far as Idaho.

The part of the plate diving eastward and downward is called the slab, which ranges from 30 to 60 miles thick as it is jammed under the North American plate. The part of the North American plate above the diving slab is shaped like a wedge.

When the leading, eastern edge of the diving slab descends deep enough, where pressures and temperatures are high, water-bearing minerals such as chlorite and amphibole release water from the slab, and the slab and surrounding mantle rock begin to melt. That is why the Cascade Range of active volcanoes extends north-to-south — above the slab and parallel but about 120 miles inland from the coast — from British Columbia south to Mount Shasta and Lassen Peak in northern California.

In the new image, yellow-orange-red areas correspond to higher electrical conductivity (or lower resistivity) in places where fluids and melts are located.

The underground image produced by the new study shows where water and molten rock accumulate atop the descending slab, and the route they take to the magma chamber that feeds eruptions of Mount Rainier:

— The rock begins to melt atop the slab about 50 miles beneath Mount Rainier. Wannamaker says it is best described as partly molten rock that contains about 2 percent water and “is a mush of crystals within an interlacing a network of molten rock.”

— Some water and partly molten rock actually gets dragged downward atop the descending slab, to depths of 70 miles or more.

— Other partly molten rock rises up through the upper mantle wedge, crosses into the crust at a depth of about 25 miles, and then rises into Rainier’s magma chamber — or at least the lobe of the chamber that crosses under the line of sensors used in the study. Evidence suggests the magma moves upward at least 0.4 inches per year.

— The new magnetotelluric image also shows a shallower zone of fluid perhaps 60 miles west of Rainier and 25 miles deep at the crust-mantle boundary. Wannamaker says it is largely water released from minerals as the slab is squeezed and heated as it dives.

The seismic data were collected during 2008-2009 for other studies. The magnetotelluric data were gathered during 2009-2010 by authors of the new study.

Wannamaker and colleagues placed an east-west line of magnetotelluric sensors: 60 that made one-day measurements and looked as deep as 30 miles into the Earth, and 20 that made measurements for a month and looked at even greater depths.

Journal Reference:

R. Shane McGary, Rob L. Evans, Philip E. Wannamaker, Jimmy Elsenbeck, Stéphane Rondenay. Pathway from subducting slab to surface for melt and fluids beneath Mount Rainier. Nature, 2014; 511 (7509): 338 DOI: 10.1038/nature13493

Note : The above story is based on materials provided by University of Utah.

Earth-like soils on Mars?

Rover image from Gale Crater reveals soil features similar to paleosols on Earth. Credit: NASA

Soil deep in a crater dating to some 3.7 billion years ago contains evidence that Mars was once much warmer and wetter, saysUniversity of Oregon geologist Gregory Retallack, based on images and data captured by the rover Curiosity.

NASA rovers have shown Martian landscapes littered with loose rocks from impacts or layered by catastrophic floods, rather than the smooth contours of soils that soften landscapes on Earth. However, recent images from Curiosity from the impact Gale Crater, Retallack said, reveal Earth-like soil profiles with cracked surfaces lined with sulfate, ellipsoidal hollows and concentrations of sulfate comparable with soils in Antarctic Dry Valleys and Chile’s Atacama Desert.

His analyses appear in a paper placed online this week by the journal Geology in advance of print in the September issue of the world’s top-ranked journal in the field. Retallack, the paper’s lone author, studied mineral and chemical data published by researchers closely tied with the Curiosity mission. Retallack, professor of geological sciences and co-director of paleontology research at the UO Museum of Natural and Cultural History, is an internationally known expert on the recognition of paleosols — ancient fossilized soils contained in rocks.

“The pictures were the first clue, but then all the data really nailed it,” Retallack said. “The key to this discovery has been the superb chemical and mineral analytical capability of the Curiosity Rover, which is an order of magnitude improvement over earlier generations of rovers. The new data show clear chemical weathering trends, and clay accumulation at the expense of the mineral olivine, as expected in soils on Earth. Phosphorus depletion within the profiles is especially tantalizing, because it attributed to microbial activity on Earth.”

The ancient soils, he said, do not prove that Mars once contained life, but they do add to growing evidence that an early wetter and warmer Mars was more habitable than the planet has been in the past 3 billion years.

Curiosity rover is now exploring topographically higher and geologically younger layers within the crater, where the soils appear less conducive to life. For a record of older life and soils on Mars, Retallack said, new missions will be needed to explore older and more clayey terrains.

Surface cracks in the deeply buried soils suggest typical soil clods. Vesicular hollows, or rounded holes, and sulfate concentrations, he said, are both features of desert soils on Earth.

“None of these features is seen in younger surface soils of Mars,” Retallack said. “The exploration of Mars, like that of other planetary bodies, commonly turns up unexpected discoveries, but it is equally unexpected to discover such familiar ground.”

The newly discovered soils provide more benign and habitable soil conditions than known before on Mars. Their dating to 3.7 billion years ago, he noted, puts them into a time of transition from “an early benign water cycle on Mars to the acidic and arid Mars of today.” Life on Earth is believed to have emerged and began diversifying about 3.5 billion years ago, but some scientists have theorized that potential evidence that might take life on Earth farther back was destroyed by plate tectonics, which did not occur on Mars.

In an email, Malcolm Walter of the Australian Centre for Astrobiology, who was not involved in the research, said the potential discovery of these fossilized soils in the Gale Crater dramatically increases the possibility that Mars has microbes. “There is a real possibility that there is or was life on Mars,” he wrote.

Retallack noted that Steven Benner of the Westheimer Institute of Science and Technology in Florida has speculated that life is more likely to have originated on a soil planet like Mars than a water planet like Earth. In an email, Benner wrote that Retallack’s paper “shows not only soils that might be direct products of an early Martian life, but also the wet-dry cycles that many models require for the emergence of life.”

Reference:
G. J. Retallack. Paleosols and paleoenvironments of early Mars. Geology, 2014; DOI: 10.1130/G35912.1

Note : The above story is based on materials provided by University of Oregon.

Brain of world’s first known predators discovered

This is a side-by-side comparison reveals the similarity between the brain of a living onychophoran (green) and that of the anomalocaridid fossil Lyrarapax unguispinus (gray). Long nerves from the frontal appendages extend to paired ganglia lying in front of the optic nerve and connect to the main brain mass in front of the mouth. Anomalocaridids had a pair of clawlike grasping appendages instead of feelers. Credit: Illustration by Nicholas Strausfeld

An international team of paleontologists has identified the exquisitely preserved brain in the fossil of one of the world’s first known predators that lived in the Lower Cambrian, about 520 million years ago. The discovery revealed a brain that is surprisingly simple and less complex than those known from fossils of some of the animal’s prey.

The find for the first time identifies the fossilized brain of what are considered the top predators of their time, a group of animals known as anomalocaridids, which translates to “abnormal shrimp.” Long extinct, these fierce-looking arthropods were first discovered as fossils in the late 19th century but not properly identified until the early 1980s. They still have scientists arguing over where they belong in the tree of life.

“Our discovery helps to clarify this debate,” said Nicholas Strausfeld, director of the University of Arizona’s Center for Insect Science. “It turns out the top predator of the Cambrian had a brain that was much less complex than that of some of its possible prey and that looked surprisingly similar to a modern group of rather modest worm-like animals.”

Strausfeld, a Regents’ Professor in the Department of Neuroscience in the UA College of Science is senior author on a paper about the findings recently published in the journal Nature.

The brain in the fossil, a new species given the name Lyrarapax unguispinus — Latin for “spiny-clawed lyre-shaped predator” — suggests its relationship to a branch of animals whose living descendants are known as onychophorans or velvet worms. These wormlike animals are equipped with stubby unjointed legs that end in a pair of tiny claws.

Onychophorans, which are also exclusively predators, grow to no more than a few inches in length and are mostly found in the Southern Hemisphere, where they roam the undergrowth and leaf litter in search of beetles and other small insects, their preferred prey. Two long feelers extend from the head, attached in front of a pair of small eyes.

The anomalocaridid fossil resembles the neuroanatomy of today’s onychophorans in several ways, according to Strausfeld and his collaborators. Onychophorans have a simple brain located in front of the mouth and a pair of ganglia — a collection of nerve cells — located in the front of the optic nerve and at the base of their long feelers.

“And — surprise, surprise — that is what we also found in our fossil,” Strausfeld said, pointing out that anomalocaridids had a pair of clawlike grasping appendages in front of the eyes.

“These top predators in the Cambrian are defined by just their single pair of appendages, wicked-looking graspers, extending out from the front of their head,” he said. “These are totally different from the antennae of insects and crustaceans. Such frontally disposed appendages are not found in any other living animals with the exception of velvet worms.”

The similarities of their brains and other attributes suggest that the anomalocaridid predators could have been very distant relatives of today’s velvet worms, Strausfeld said.

“This is another contribution towards the new field of research we call neuropaleontology,” said Xiaoya Ma of the Natural History Museum in London, a co-author on the paper. “These grasping appendages are a characteristic feature of this most celebrated Cambrian animal group, whose affinity with living animals has troubled evolutionary scientists for almost a century. The discovery of preserved brain in Lyrarapax resolves specific anatomical correspondences with the brains of onychophorans.”

“Being able to directly associate appendages with parts of the brain in Cambrian animals is a huge advantage,” said co-author Gregory Edgecombe, also at the Natural History Museum. “For many years now paleontologists have struggled with the question of how different kinds of appendages in Cambrian fossils line up with each other and with what we see in living arthropods. Now for the first time, we didn’t have to rely just on the external form of the appendages and their sequence in the head to try and sort out segmental identities, but we can draw on the same tool kit we use for extant arthropods — the brain.”

Strausfeld and his colleagues recently presented evidence of the oldest known fossil of a brain belonging to arthropods related to insects and crustaceans and another belonging to a creature related to horseshoe crabs and scorpions (see links below).

“With this paper and our previous reports in Nature, we have identified the three principal brain arrangements that define the three groups of arthropods that exist today,” Strausfeld said. “They appear to have already coexisted 520 million years ago.”

The Lyrarapax fossil was found in 2013 by co-author Peiyun Cong near Kunming in the Chinese province of Yunnan. Co-authors Ma and Edgecombe participated in the analysis, as did Xianguang Hou — who discovered the Chengjiang fossil beds in 1984 ¬ — at the Yunnan Key Laboratory for Paleobiology at the University of Yunnan.

“Because its detailed morphology is exquisitely preserved, Lyrarapax is amongst the most complete anomalocaridids known so far,” Cong said.

Just over five inches long, Lyrarapax was dwarfed by some of the larger anomalocaridids, which reached more than three feet in length. Paleontologists excavating lower Cambrian rocks in southern Australia found that some anomalocaridids had huge compound eyes, up to 10 times larger than the biggest dragonfly eye, befitting what must have been a highly efficient hunter, Strausfeld said.

The fact that the brain of the earliest known predator appears much simpler in shape than the previously unearthed brains of its contemporaries begs intriguing questions, according to Strausfeld, one of which is whether it is possible that predators drove the evolution of more complex brains.

“With the evolution of dedicated and highly efficient predators, the pressure was on other animals to be able to detect and recognize potential danger and rapidly coordinate escape movements. These requirements may have driven the evolution of more complex brain circuitry,” Strausfeld said.

Journal Reference:

Peiyun Cong, Xiaoya Ma, Xianguang Hou, Gregory D. Edgecombe, Nicholas J. Strausfeld. Brain structure resolves the segmental affinity of anomalocaridid appendages. Nature, 2014; DOI: 10.1038/nature13486

Note : The above story is based on materials provided by University of Arizona. The original article was written by Daniel Stolte.

Animal foraging tactics unchanged for 50 million years

Fossilized sea urchin tracks at Zumaia. Credit: Richard Twitchett / Trustees NHM

Animals have used the same technique to search for food that’s in short supply for at least 50 million years, a University of Southampton-led study suggests.
Researchers analysed fossilised sea urchin trails from northern Spain and found the tracks reflect a search pattern still used by a huge range of creatures today.

But this is the first example of extinct animals using such a strategy.

The findings could explain why so many modern animals use the technique, and suggest the pattern may have an even more ancient origin.

Creatures including sharks, honeybees, albatrosses and penguins all search for food according to a mathematical pattern of movement called a Lévy walk — a random search strategy made up of many small steps combined with a few longer steps. Although a Lévy walk is random, it’s the most efficient way to find food when it’s scarce.

David Sims, Professor of Marine Ecology at the University of Southampton and lead author of the study, says: “How best to search for food in complex landscapes is a common problem facing all mobile creatures.

“Finding food in a timely fashion can be a matter of life or death for animals — choose the wrong direction to move in often enough and it could be curtains. But moving in a random search pattern called a Lévy walk is mathematically the best way to find isolated food.”

Even though a wide range of modern creatures search for food according to this pattern, scientists had no idea how the pattern came about, until now.

Professor Sims and colleagues from the University of Southampton, NERC’s National Oceanography Centre, Rothamsted Research, VU University Amsterdam and the Natural History Museum analysed the fossilised Eocene-era tracks that were made by sea urchins that lived on the deep sea floor around 50 million years ago. The long trails are preserved in rocky cliffs in a region called Zumaia in northern Spain.

“Finding the signature of an optimal behaviour in the fossil record is exceedingly rare and will help to understand how ancient animals survived very harsh conditions associated with the effects of dramatic climate changes,” says Professor Sims, who is currently seconded to the Marine Biological Association in Plymouth. “Perhaps it’s a case of when the going got tough, the tough really did get going.”

“The patterns are striking, because they indicate optimal Lévy walk searches likely have a very ancient origin and may arise from simple behaviours observed in much older fossil trails from the Silurian period, around 440 million years ago,” he adds.

Professor Richard Twitchett of the Natural History Museum and co-author of the study adds: “It’s amazing to think that 50 million-year-old fossil burrows and trails have provided us with the first evidence of foraging strategies in animals that live on and in the deep-sea floor — studies which would be nearly impossible and very expensive to do in modern oceans.

“Trace fossils are remarkable and beautiful records of the movements of ancient animals, which have been frozen in time and tell us so much about the evolution of life on Earth and the environments of the past.”

The researchers think the collapse of primary producers, such as phytoplankton, and widespread food scarcity caused by mass extinctions, which show up in the fossil record, could have triggered the evolution of Lévy-like searches.

The Eocene lasted from 56 to 33.9 million years ago, and began as a time of global warming, with temperatures soaring across the planet.

Lévy walks aren’t just confined to animals; our ancient hunter-gatherer ancestors used exactly the same approach, as do modern hunter-gatherers in northern Tanzania.

The study is published in The Proceedings of the National Academy of Sciences.

Journal Reference:

D. W. Sims, A. M. Reynolds, N. E. Humphries, E. J. Southall, V. J. Wearmouth, B. Metcalfe, R. J. Twitchett. Hierarchical random walks in trace fossils and the origin of optimal search behavior. Proceedings of the National Academy of Sciences, 2014; DOI: 10.1073/pnas.1405966111

Note : The above story is based on materials provided by University of Southampton.

Rainwater discovered at new depths, with high pressure and temperatures over 300 degrees Celsius

The Southern Alps Mountain Range, New Zealand. Rain and snow falling on the mountains percolate to great depths. Credit: Simon Cox

University of Southampton researchers have found that rainwater can penetrate below the Earth’s fractured upper crust, which could have major implications for our understanding of earthquakes and the generation of valuable mineral deposits.
It had been thought that surface water could not penetrate the ductile crust — where temperatures of more than 300°C and high pressures cause rocks to flex and flow rather than fracture — but researchers, led by Southampton’s Dr Catriona Menzies, have now found fluids derived from rainwater at these levels.

Fluids in the Earth’s crust can weaken rocks and may help to initiate earthquakes along locked fault lines. They also concentrate valuable metals such as gold. The new findings suggest that rainwater may be responsible for controlling these important processes, even deep in the Earth.

Researchers from the University of Southampton, GNS Science (New Zealand), the University of Otago, and the Scottish Universities Environmental Research Centre studied geothermal fluids and mineral veins from the Southern Alps of New Zealand, where the collision of two tectonic plates forces deeper layers of the Earth closer to the surface.

The team looked into the origin of the fluids, how hot they were and to what extent they had reacted with rocks deep within the mountain belt.

“When fluids flow through the crust they leave behind deposits of minerals that contain a small amount of water trapped within them,” says Postdoctoral Researcher Catriona, who is based at the National Oceanography Centre. “We have analysed these waters and minerals to identify where the fluids deep in the crust came from.

“Fluids may come from a variety of sources in the crust. In the Southern Alps fluids may flow upwards from deep in the crust, where they are released from hot rocks by metamorphic reactions, or rainwater may flow down from the surface, forced by the high mountains above. We wanted to test the limits of where rainwater may flow in the crust. Although it has been suggested before, our data shows for the first time that rainwater does penetrate into rocks that are too deep and hot to fracture.”

Surface-derived waters reaching such depths are heated to over 400°C and significantly react with crustal rocks. However, through testing the researchers were able to establish the water’s meteoric origin.

Funding for this research, which has been published in Earth and Planetary Science Letters, was provided by the Natural Environmental Research Council (NERC). Catriona and her team are now looking further at the implications of their findings in relation to earthquake cycles as part of the international Deep Fault Drilling Project, which aims to drill a hole through the Alpine Fault at a depth of about 1km later this year.

Journal Reference:
Catriona D. Menzies, Damon A.H. Teagle, Dave Craw, Simon C. Cox, Adrian J. Boyce, Craig D. Barrie, Stephen Roberts. Incursion of meteoric waters into the ductile regime in an active orogen. Earth and Planetary Science Letters, 2014; 399: 1 DOI: 10.1016/j.epsl.2014.04.046

Note : The above story is based on materials provided by University of Southampton.

Are ants the answer to carbon dioxide sequestration?

A 25-year-long study provides the first quantitative measurement of in situ calcium-magnesium silicate mineral dissolution by ants, termites, tree roots, and bare ground. Credit: © Miroslav Beneda / Fotolia

A 25-year-long study published in Geology on 14 July provides the first quantitative measurement of in situ calcium-magnesium silicate mineral dissolution by ants, termites, tree roots, and bare ground. This study reveals that ants are one of the most powerful biological agents of mineral decay yet observed. It may be that an understanding of the geobiology of ant-mineral interactions might offer a line of research on how to “geoengineer” accelerated CO2 consumption by Ca-Mg silicates.

Researcher Ronald Dorn of Arizona State University writes that over geological timescales, the dissolution of calcium (Ca) and magnesium (Mg) bearing silicates has led to the graduate drawdown of atmospheric carbon dioxide (CO2) through the accumulation of limestone and dolomite. Many contemporary efforts to sequester CO2 involve burial, with some negative environmental consequences.

Dorn suggests that, given that ant nests as a whole enhance abiotic rates of Ca-Mg dissolution by two orders of magnitude (via biologically enhanced weathering), future research leading to the isolation of ant-based enhancement process could lead to further acceleration. If ant-based enhancement could reach 100 times or greater, he writes, this process might be able to geo-engineer sequestration of CO2 from the atmosphere. Similarly, ants might also provide clues on geoengineering efficient pathways of calcium carbonate precipitation to sequester atmospheric CO2.

Earth’s climate has cooled significantly over the past 65 m.y., likely from hydrologic regulation, vegetation change, and interactions related to tectonism, in part mediated by Ca-Mg silicate mineral dissolution that draws down CO2. Although speculative, says Dorn, the timing of the expansion in the variety and number of ants in the Paleogene and the Neogene suggests that biologically enhanced weathering by ants could potentially be a part of the puzzle of Cenozoic cooling.

Journal Reference:

R. I. Dorn. Ants as a powerful biotic agent of olivine and plagioclase dissolution. Geology, 2014; DOI: 10.1130/G35825.1

Note : The above story is based on materials provided by Geological Society of America.

New feathered predatory fossil sheds light on dinosaur flight

This is an illustration of newly discovered feathered dinosaur, Changyuraptor yangi. Credit: S. Abramowicz, Dinosaur Institute, NHM

A new raptorial dinosaur fossil with exceptionally long feathers has provided exciting insights into dinosaur flight. A paper published in Nature Communications on July 15, 2014 asserts that the fossil — discovered by an international team led by Natural History Museum of Los Angeles County (NHM) paleontologist Dr. Luis Chiappe — has a long feathered tail that Chiappe and co-authors believe was instrumental for decreasing descent speed and assuring safe landings.

The 125-million-year-old dinosaur, named Changyuraptor yangi, was found in the Liaoning Province of northeastern China. The location has seen a surge of discoveries in feathered dinosaurs over the last decade. The newly discovered, remarkably preserved dinosaur sports a full set of feathers cloaking its entire body, including the extra-long tail feathers. “At a foot in length, the amazing tail feathers of Changyuraptor are by far the longest of any feathered dinosaur,” said Chiappe.

Analyses of the bone microstructure by University of Cape Town (South Africa) scientist, Dr. Anusuya Chinsamy, shows that the raptor was a fully grown adult, and tipping the scale at nine pounds, the four-foot-long Changyuraptor is the biggest of all four-winged dinosaurs. These microraptorine dinosaurs are dubbed “four-winged” because the long feathers attached to the legs have the appearance of a second set of wings. In fact, the long feathers attached to both legs and arms of these ancient predators have led researchers to conclude that the four-winged dinosaurs were capable of flying. “Numerous features that we have long associated with birds in fact evolved in dinosaurs long before the first birds arrived on the scene,” said co-author Dr. Alan Turner of Stony Brook University (New York). “This includes things such as hollow bones, nesting behavior, feathers…and possibly flight.”

How well these creatures used the sky as a thoroughfare has remained controversial. The new discovery explains the role that the tail feathers played during flight control. For larger flyers, safe landings are of particular importance. “It makes sense that the largest microraptorines had especially large tail feathers — they would have needed the additional control,” added Dr. Michael Habib, a researcher at the University of Southern California and a co-author of the paper.

The discovery of Changyuraptor consolidates the notion that flight preceded the origin of birds, being inherited by the latter from their dinosaurian forerunners. “The new fossil documents that dinosaur flight was not limited to very small animals but to dinosaurs of more substantial size,” said Chiappe. “Clearly far more evidence is needed to understand the nuances of dinosaur flight, but Changyuraptor is a major leap in the right direction.”

Note : The above story is based on materials provided by Natural History Museum of Los Angeles County.

Bones of elephant ancestor unearthed: Meet the gomphothere

Gomphothere mandible uncovered at El Fin del Mundo. Archaeologists working in northwestern Mexico were not sure what kind of animal they had unearthed until they found this telltale jawbone, which belonged to a gomphothere. Credit: Joaquin Arroyo-Cabrales

An animal once believed to have disappeared from North America before humans ever arrived there might actually have roamed the continent longer than previously thought — and it was likely on the list of prey for some of continent’s earliest humans, researchers from the University of Arizona and elsewhere have found.
Archaeologists have discovered artifacts of the prehistoric Clovis culture mingled with the bones of two gomphotheres, ancient ancestors of the elephant, at an archaeological site in northwestern Mexico.

The discovery suggests that the Clovis — the earliest widespread group of hunter-gatherers to inhabit North America — likely hunted and ate gomphotheres. The members of the Clovis culture were already well-known as hunters of the gomphotheres’ cousins, mammoths and mastodons.

Although humans were known to have hunted gomphotheres in Central America and South America, this is the first time a human-gomphothere connection has been made in North America, says archaeologist Vance Holliday, who co-authored a new paper on the findings, published this week in Proceedings of the National Academy of Sciences.

“This is the first archaeological gomphothere found in North America, and it’s the only one known,” said Holliday, a professor of anthropology and geology at the UA.

Holliday and colleagues from the U.S. and Mexico began excavating the skeletal remains of two juvenile gomphotheres in 2007 after ranchers alerted them that the bones had been found in northwestern Sonora, Mexico.

They didn’t know at first what kind of animal they were dealing with.

“At first, just based on the size of the bone, we thought maybe it was a bison, because the extinct bison were a little bigger than our modern bison,” Holliday said.

Then, in 2008, they discovered a jawbone with teeth, buried upside down in the dirt.

“We finally found the mandible, and that’s what told the tale,” Holliday said.

Gomphotheres were smaller than mammoths — about the same size as modern elephants. They once were widespread in North America, but until now they seemed to have disappeared from the continent’s fossil record long before humans arrived in North America, which happened some 13,000 to 13,500 years ago, during the late Ice Age.

However, the bones that Holliday and his colleagues uncovered date back 13,400 years, making them the last known gomphotheres in North America.

The gomphothere remains weren’t all Holliday and his colleagues unearthed at the site, which they dubbed El Fin del Mundo — Spanish for The End of the World — because of its remote location.

As their excavation of the bones progressed, they also uncovered numerous Clovis artifacts, including signature Clovis projectile points, or spear tips, as well as cutting tools and flint flakes from stone tool-making. The Clovis culture is so named for its distinctive stone tools, first discovered by archaeologists near Clovis, New Mexico, in the 1930s.

Radiocarbon dating, done at the UA, puts the El Fin del Mundo site at about 13,400 years old, making it one of the two oldest known Clovis sites in North America; the other is the Aubrey Clovis site in north Texas.

The position and proximity of Clovis weapon fragments relative to the gomphothere bones at the site suggest that humans did in fact kill the two animals there. Of the seven Clovis points found at the site, four were in place among the bones, including one with bone and teeth fragments above and below. The other three points had clearly eroded away from the bone bed and were found scattered nearby.

“This is the first Clovis gomphothere, it’s the first archaeological gomphothere found in North America, it’s the first evidence that people were hunting gomphotheres in North America, and it adds another item to the Clovis menu,” Holliday said.

The dig at El Fin del Mundo, a joint effort between the U.S. and Mexico, was funded by the UA School of Anthropology’s Argonaut Archaeological Research Fund, the National Geographic Society, the Instituto Nacional de Antropología e Historia and The Center for Desert Archaeology in Tucson.

In addition to Holliday, authors of the PNAS paper include: lead author Guadalupe Sanchez, who has a doctorate in anthropology from the UA; UA alumni Edmund P. Gaines and Susan M. Mentzer; UA doctoral candidates Natalia Martínez-Tagüeña and Andrew Kowler; UA master’s student Ismael Sanchez-Morales; UA scientists Todd Lange and Gregory Hodgins; and Joaquin Arroyo-Cabrales at the Instituto Nacional de Antropología e Historia.

Note : The above story is based on materials provided by University of Arizona.

Short lives, violent deaths: Two CT-scanned Siberian mammoth calves yield trove of insights

CT images showing a side-by-side comparison of skulls from Lyuba (left) and Khroma, with bones of the front of the skull shown below. Credit: University of Michigan Museum of Paleontology

CT scans of two newborn woolly mammoths recovered from the Siberian Arctic are revealing previously inaccessible details about the early development of prehistoric pachyderms. In addition, the X-ray images show that both creatures died from suffocation after inhaling mud.
Lyuba and Khroma, who died at ages 1 and 2 months, respectively, are the most complete and best-preserved baby mammoth specimens ever found. Lyuba’s full-body CT scan, which used an industrial scanner at a Ford testing facility in Michigan, was the first of its kind for any mammoth.

“This is the first time anyone’s been able to do a comparative study of the skeletal development of two baby mammoths of known age,” said University of Michigan paleontologist Daniel Fisher.

“This allowed us to document the changes that occur as the mammoth body develops,” Fisher said. “And since they are both essentially complete skeletons, they can be thought of as Rosetta Stones that will help us interpret all the isolated baby mammoth bones that show up at other localities.”

Fisher, director of the U-M Museum of Paleontology, is lead author of a paper published online July 8 in a special issue of the Journal of Paleontology. The paper provides a detailed discussion of the findings from the Lyuba and Khroma CT scans and includes about 30 previously unpublished CT images.

The paper’s 10 authors are from the United States, Russia and France. They include three recent U-M graduates and a collections manager at the U-M paleontology museum.

Siberian permafrost yields mammoth surprises

Lyuba and Khroma lived more than 40,000 years ago and belonged to mammoth populations separated by roughly 3,000 miles. Lyuba was found by reindeer herders in May 2007 on the banks of the Yuribei River on the Yamal Peninsula, in northwest Siberia. She was found frozen and partially dehydrated but otherwise appeared to be intact, except for the loss of most of her hair and all of her nails.

Khroma was found in October 2008 near the Khroma River in northernmost Yakutia, in northeast Siberia. She was frozen in permafrost in an upright position. Ravens and possibly arctic foxes scavenged exposed portions of her carcass, including parts of the trunk and skull and the fat hump that likely covered the back of her neck. Otherwise, the body was recovered in good condition.

Because of the remarkable preservation of Lyuba and Khroma, stringent conditions were placed on their study. Some dissection and limited sampling were allowed, but both specimens were left mostly intact. CT scans offered a non-destructive means of visualizing and analyzing much of their anatomy without compromising exhibit potential or options for future analysis.

CT scans of Lyuba were done in Tokyo in 2009 and in Wisconsin in 2010, using medical scanners. But because of Lyuba’s size (about 110 pounds and slightly smaller than a baby elephant), the researchers could not acquire 3-D data from her entire body. They finally succeeded in October 2010 at Ford Motor Co.’s Nondestructive Evaluation Laboratory in Livonia, Mich., using a scanner designed for finding flaws in vehicle transmissions.

Khroma’s CT scans were done at two French hospitals. Micro-CT scans of teeth from both mammoth calves were conducted at the University of Michigan School of Dentistry. From the dental studies, Fisher and colleagues determined that Lyuba died 30 to 35 days after birth and estimated that Khroma’s age at death was between 52 and 57 days.

Dating technique more than 30 years in the making

The researchers used a technique developed by Fisher over the past 30-plus years that involves counting daily growth layers inside the teeth, a bit like counting the annual growth rings on a tree to determine its age. The dental studies also indicate that both mammoths were born in the spring.

Scans of Khroma’s skull showed she had a brain slightly smaller than that of a newborn elephant, which hints at the possibility of a shorter gestation period for mammoths.

Lyuba’s skull is conspicuously narrower than Khroma’s, and her upper jawbones are more slender, while Khroma’s shoulder blades and foot bones are more developed. These differences may simply reflect the one-month age difference between the calves, or they could relate to the different populations from which the two calves derived.

The researchers refer to both calves as mummies due to the high level of soft-tissue preservation. In addition to fully articulated skeletons, the carcasses held preserved muscle, fat, connective tissue, organs and skin. Khroma even had clotted blood inside intact blood vessels and undigested milk in the stomach.

“These two exquisitely preserved baby mammoths are like two snapshots in time. We can use them to understand how factors like location and age influenced the way mammoths grew into the huge adults that captivate us today,” said co-author Zachary T. Calamari of the American Museum of Natural History, who began investigating mammoths as a U-M undergraduate working with Fisher.

Short lives, violent deaths

In addition to providing unprecedented insights into mammoth development, the CT scans of Lyuba and Khroma show that both youngsters died after inhaling mud, then suffocating, according to the authors of the Journal of Paleontology paper. This death scenario was suggested for Lyuba shortly after she was first examined. The Khroma CT scans demonstrate that she suffered a similar fate.

In Lyuba, the scans revealed a solid mass of fine-grained sediment blocking the air passages in the middle of the trunk. Sediment was also seen in Lyuba’s throat and bronchial passages. If Lyuba had died by drowning rather than suffocation — as some have suggested — then traces of sediment should also have been detected in parts of the lungs beyond the bronchial passages, but that was not the case.

Slightly coarser sediment was found in Khroma’s trunk, mouth and throat. Her lungs weren’t available for study because they were scavenged before the carcass was recovered. Since both animals appear to have been healthy at the time of death, a “traumatic demise” involving the inhalation of mud and suffocation appears to be the most likely cause of death in both cases, according to the authors.

The researchers suspect that Lyuba died in a lake because sediments found in her respiratory tract include fine-grained vivianite, a deep blue iron- and phosphate-bearing mineral that commonly forms in cold, oxygen-poor settings such as lake bottoms.

It’s possible that Lyuba crashed through the ice while crossing a lake during the spring melt. If she was struggling to breathe while submerged in a frigid lake, the mammalian “diving reflex” may have kicked in during her final moments, Fisher said. The reflex is triggered by cold water contacting the face, and it initiates physiological changes that enable animals to stay underwater for extended periods of time.

Those changes include a shifting of blood from the extremities to the body’s core, including the brain and heart. The blood shift would help explain small vivianite nodules found on Lyuba’s facial tissues during a necropsy. The CT scans revealed vivianite nodules, up to several millimeters in length, on the surface of the skull and inside it.

Blood provided iron source for vivianite nodules?

Blood coursing into Lyuba’s brain, due to the mammalian diving reflex, may have provided the iron source for the vivianite nodules, according to the authors. Lactic acid-producing bacteria ate away at her bones after death, possibly liberating the phosphate ions used to make vivianite, Fisher said.

A possible death scenario for Khroma places the calf and her mother on a riverbank in the spring. Khroma had been nursing less than an hour before her death, as evidenced by undigested milk found in her stomach during a necropsy by a team of scientists that included Fisher.

“It looked like you’d just popped the top on a container of yogurt,” Fisher recalled. “It was that white. It was that smooth. Just fresh, creamy milk from mama mammoth.”

Perhaps the riverbank collapsed and the two mammoths, mother and daughter, plunged into the river. A fall would account for the fractured spinal column revealed by Khroma’s CT scan, as well as the mud she inhaled.

The CT scan paper is part of a special Journal of Paleontology issue on three-dimensional visualization and analysis of fossils. In addition to Fisher and Calamari, the paper’s authors are Ethan A. Shirley, Christopher D. Whalen and Adam Rountrey of the U-M Museum of Paleontology; Alexei N. Tikhonov of the Russian Academy of Sciences; Bernard Buigues of the International Mammoth Committee in France; Frederic Lacombat of the Musee de Paleontologie de Chilhac in France; and Semyon Grigoriev and Piotr A. Lazarev of the North-Eastern Federal University in Russia.

Fisher is the Claude W. Hibbard Collegiate Professor of Paleontology, a professor in the Department of Earth and Environmental Sciences, and a professor in the Department of Ecology and Evolutionary Biology. Calamari, Shirley and Whalen are recent U-M graduates and spent a month in Siberia with Fisher in 2012, searching for mammoth remains. Rountrey is the collections manager for vertebrates at the U-M Museum of Paleontology.

The research was supported by the U.S. National Science Foundation and by the National Geographic Society.

Note : The above story is based on materials provided by University of Michigan.

Pyrophyllite

Pyrophyllite Champion Mine, White Mts, Mono County, California size: 4.0 x 3.0 x 2.3 cm© Rob Lavinsky / iRocks

Chemical Formula: Al2(Si4O10)(OH)2
Locality: Tres Cerritos, California, USA; Pyschminsk and Beresovsk, Ural Mountains, Russia.
Name Origin: From the Greek for fie and leaf, in allusion to its tendency to exfoliate into fan shapes when heated.

Pyrophyllite is a phyllosilicate mineral composed of aluminium silicate hydroxide: Al2(Si4O10)(OH)2. It occurs in two more or less distinct varieties, namely, as crystalline folia and as compact masses; distinct crystals are not known.

The folia have a pronounced pearly lustre, owing to the presence of a perfect cleavage parallel to their surfaces: they are flexible but not elastic, and are usually arranged radially in fan-like or spherical groups. This variety, when heated before the blowpipe, exfoliates and swells up to many times its original volume, hence the name pyrophyllite, from the Greek pyros (fire) and phyllos (a leaf), given by R. Hermann in 1829. The color of both varieties is white, pale green, greyish or yellowish; they are very soft (hardness of 1 to 1.5) and are greasy to the touch. The specific gravity is 2.65 – 2.85. The two varieties are thus very similar to talc.

History

Authors: WARDLE & BRINDLEY
Discovery date : 1972
Town of Origin : PYSCHMINSK et BEREZOV, OURAL
Country of Origin: RUSSIE ex-URSS

Chemical properties

Chemical Class : PHYLLOSILICATES
Subclass : Phyllosilicates
Chemical Formula : Al2(Si4O10)(OH)2

Crystallographical properties

Crystalline System: Triclinic
Symmetry Class: 31;32
Network System: Center C  –
a : 5,16
b : 8,96
c : 9,34
Alpha : 91,18
Beta : 100,46
Gamma : 89,64
Z : Formula units per unit cell : 2

Optical properties

Optical and misc. Properties: Translucide –  Opaque

Physical properties

Hardness : from 1,00 to 2,00
Density : 2,70
Color : pearl-white; yellow; brown yellow; pale blue; grey green; grayish green; bluish green
Streak: white
Cleavage: yes

Photos:

Pyrophyllite Locality: Hillsboro District, Orange County, North Carolina, USA Size: 11 x 7.3 x 6.6 cm. © Rob Lavinsky / iRocks
Locality: Cottonstone Mountain, Mecklenburg County, North Carolina, USA Source: University of Arizona Mineral Museum 13207 [view label] Owner: RRUFF
Pyrophyllite Locality: Hillsboro District, Orange County, North Carolina, USA 9.6 x 5.5 x 5.4 cm © Rob Lavinsky / iRocks
from Indian Gulch, Mariposa County, California. Theis sample displayed in the Smithsonian Museum of Natural History.

What geology has to say about global warming

Cobscook Bay State Park, Maine. Credit: W. Menke

Last month I gave a public lecture entitled, “When Maine was California,” to an audience in a small town in Maine. It drew parallels between California, today, and Maine, 400 million years ago, when similar geologic processes were occurring. Afterward, a member of the audience asked me what geology had to say about global warming. The following is an expanded version of my answer. Note that I use the word geology to mean any element of the earth sciences that is focused on earth history, and do not distinguish the many sub-disciplines about which a specialist would be familiar.
Geologists think of the last 50 million years as the recent past, both because they represents only about one percent of the age of the earth, and because plate tectonics, the geologic process that controls conditions within the solid part of the earth, has operated without major change during that time period. This is the time period that is most relevant to gaining insights about earth’s climate that can be applied to the present-day global warming debate.

The geological record of ancient climate is excellent. Ancient temperatures can be determined very precisely, because the composition of the shells of corals and other marine organisms varies measurably with it. Furthermore, the plants and animals that lived during a given time and are now preserved as fossils indicate whether the climate was wet or dry. The overall climatic trend has been cooling, from an unusually warm period, called the Eocene Optimum, 55-45 million years ago, to an unusually cool period, colloquially called the Ice Age, which ended just 20,000 years ago. The overall range in temperature was enormous, about 35°F. The earth was so warm during the Eocene Optimum that Antarctica was ice-free; ice caps did not start to form there until about 35 million years ago. Palm trees grew at high latitudes and cold-blooded animals, such as crocodiles, lived in the Arctic.

Lesson 1. The earth’s climate (including its average temperature) is highly variable.

Notwithstanding very divergent conditions, life flourished both during the Eocene Optimum and the Ice Age, though in both cases life was more abundant in some parts of the world than in others. The fossil record indicates that forests were common during the Eocence Optimum, yet some areas were sparsely vegetated steppes and deserts. While the great glaciers of the Ice Age were lifeless, extremely large mammals such as Woolly Mammoth and Giant Ground Sloth inhabited lower latitudes. The changing climate produced both winners and losers. Some species adapted; others went extinct.

Lesson 2. Life flourished during both warm and cold periods; changes in climate produced both winners and losers.

An important issue is whether climate variability is due to processes occurring on the earth, or to changes in the intensity of sunlight – for it’s the sun that keeps our planet warm. The geological evidence, though subtle, strongly supports earthly, and not solar, causes. This evidence is drawn from the study of the many shorter period climate fluctuations, some which last millions of years and other just thousands, which are superimposed on the long-term cooling trend.

Climate during the Ice Age (the last 4 million years) has been particularly unstable, with many swings of more than 10°F. These fluctuations are recorded in the annual layers of snow preserved in glaciers and in marine sediments, whose properties track the temperature at which they were formed. The timing of these swings closely follows regular fluctuations in the tilt of the earth’s axis and the shape of its orbit around the sun. Called Milankovitch cycles, they are due to the gravitational influence of the moon and planets. Their magnitude can be reliably calculated, since they are due to fluctuations of the position and orientation of the earth relative to the sun, and not to any change in the sun’s brightness. Surprisingly, they are too small to account for the large swings in temperature, unless the earth’s climate system is acting to amplify them. Here’s the subtle part of the argument: This mismatch between the feeble amplitude of the Milankovitch cycles and the large swings in climate is strong evidence that internal processes can cause strong climate variability.

Lesson 3. Variations in climate are mainly due to processes occurring on the earth, as contrasted to in the sun.

Ice Age carbon dioxide levels are well known, because bubbles of Ice Age air are preserved within the Antarctic and Greenland glaciers. More ancient carbon dioxide levels are difficult to measure, since no samples of older air have been preserved. Several indirect methods are in use, one based on the effect of ocean carbon dioxide levels on the composition of marine sediments, and another on its effect on now-fossil plant leaves. These measurements show fairly convincingly that the long-term cooling trend over the last 50 million years is associated with a gradual decrease in carbon dioxide levels, from 2000-3000 parts per million during the Eocene Optimum to 200 p.p.m. during the Ice Age. The cause of this decrease is not fully understood, but seems to indicate that the total amount of carbon that can influence climate (carbon in the atmosphere, biosphere and ocean) is slowly decreasing, possibly because an increasing amount of carbon is being tied up in sedimentary rocks such as limestone.

Lesson 4. Atmospheric carbon dioxide levels are highly variable, with the highest levels being associated with warm periods and the lowest levels associated with cold periods.

The correlation of atmospheric temperature with carbon dioxide reflects the latter’s role as a greenhouse gas. By absorbing heat radiated from the earth’s surface and re-radiating it back downward, it causes the earth’s surface to be warmer than it otherwise would be. The earth would be uninhabitable without the greenhouse effect, as can be seen by comparing the earth’s average temperature of about 60°F to the minus 100°F average temperature of the moon, which receives exactly the same amount of sunlight. An important question is whether the high carbon dioxide level at the time of the Eocene Optimum was the cause of the high temperatures that occurred during that time period.

Ascribing causes to fluctuation in climate is a tricky business, because atmospheric carbon dioxide level is only one factor among several that determine earth’s climate. Other important factors include: the amount of water vapor (another greenhouse gas) in the atmosphere; the percentage of the sky covered by clouds, which reflect sunlight back into space; the percent of land covered with ice and snow, which are also very reflective; and the percentage covered by oceans and and forests, which are very absorbing. All factors act together to maintain a given temperature; yet they feed back upon one another in complicated ways. Thus, for instance, had the Antarctic been glaciated during the Eocene Optimum (and the geological evidence is that it was ice-free), the world would have been somewhat cooler due to the high reflectivity of the ice. On the other hand, glaciers were absent precisely because the world was so warm. Geologic evidence alone cannot prove that the high levels of atmospheric carbon dioxide during the Eocene Optimum caused the high temperatures then, since the contribution of other factors, such as clouds and water vapor are unknown. Nevertheless, global climate models seem to indicate that such a high temperature only can be maintained in a world with high carbon dioxide; no other combination of factors can explain it.

Changing global temperatures induce changes in patterns of rainfall, winds and ocean currents, all of which can have a profound effect on the ecosystem of a given region. A large decrease in rainfall will, of course, turn rainforest into a desert. However, geology has few specifics to offer on the subject of how any particular region will be affected. The factors that cause climate change at a given geographical location are too varied to allow convincing geological analogues. However, geology shows that variability is the norm. Some of today’s deserts were forested a few million years ago, and some of today’s forests were formerly deserts. From the human perspective, climate change has the potential of causing some areas to become less agriculturally productive (and therefore less inhabitable), and other to become more so.

Lesson 5. Local climates are very variable, changing dramatically over periods of thousands to millions of years.

Changing global temperature can cause a rise or fall in sea level due to the accumulation or melting of glacial ice. This effect is global in extent and one that can have an extremely deleterious effect on us human beings, since so many of us live near the coast. The geological evidence is very strong that sea level was higher by about 200 feet at times, such as during the Eocene Optimum, when Antarctica was ice-free, and was about 400 feet lower during the height of the Ice Age. The range is enormous; the world’s coastlines are radically altered by such changes. The continental shelves were substantially exposed during the low stands, and many low-lying coastal areas were underwater during the high stands. Woolly Mammoths roamed hundreds of miles offshore of Virginia during the Ice Age. Beach sand deposits in inland North Carolina indicate that the shoreline was far inland during the Eocene Optimum.

Lesson 6. Sea level has fluctuated as the world’s glaciers grow or recede, and was about 200 feet higher at times when Antarctica was ice-free.

Carbon dioxide levels have risen since the end of the Ice Age, first to a natural level of about 280 p.p.m. just before the start of the Industrial Era, and then to 400 p.p.m. as people burned coal and petroleum in large quantities. Carbon dioxide is currently increasing at a rate of about 2.6 p.p.m. per year.

A critical question is the level of atmospheric carbon dioxide 35 million years ago, when glaciers began to form in Antarctica, for it serves as a rough estimate of the concentration needed to melt present-day Antarctica. It’s a rough estimate only, for geological conditions were not exactly the same now and then. In particular, strong ocean currents that today keep warmer waters away from Antarctica were not present 35 million years ago, owing to the somewhat different configuration of tectonic plates. Unfortunately, the best currently-available estimates of atmospheric carbon dioxide during this critical time period have large uncertainties. Carbon dioxide decreased from 600-1400 p.p.m. at the start of the glaciations to 400-700 p.p.m. several million years later. These measurements are consistent with modeling results, which give a threshold of about 780 p.p.m. for the formation of a continental-scale ice cap on Antarctica. This value will be reached by the year 2150 at the present growth rate of atmospheric carbon dioxide – or sooner if emission rates continue to soar – suggesting that Antarctica will be at risk of melting at that time.

Antarctic ice will not melt overnight even should the threshold be reached. The deglaciation at the end of the Ice Age provides a useful example. The rate of sea level rise was initially low, just one-tenth of an inch per year. It then gradually increased, peaking at about 3 inches per year about 14,000 years ago, which was about 5,000 years after the start of the deglaciation. This rate persisted for 1,600 years, during which time sea level rose a total of 60 feet. The average rate of sea level rise was slower, about a half-inch per year.

Lesson 7. Sea level rise as fast as a few inches per year can persist over thousands of years.

The most extreme scenario for future carbon dioxide levels considered by the Intergovernmental Panel on Climate Change (IPCC) predicts about 0.4 inches per year of sea level rise over the next century. This rate is less than, but similar in magnitude, to the average rate during the Ice Age deglaciation, but considerably smaller than its peak. Because of its focus on the current century, a reader of the IPCC report might be left with the sense that sea level rise will be over by 2100. Precisely the opposite is true! Geology demonstrates that melting accelerates with time and can last for several thousand years.

The most important lessons drawn from geology are that the earth’s climate can change radically and that the pace of change can be rapid. Geology also supports the theory that past periods of especially warm temperature were caused by high atmospheric carbon dioxide level. Of the many effects of global warming, geology is currently most relevant to sea level rise caused by melting glaciers. The precision of the measurement is currently too poor to give an exact answer to a critical question, At what carbon dioxide level are we in danger of melting Antarctica? However, while crude, these estimates suggest that this threshold will be reached in 150-300 years, if carbon dioxide levels continue to rise at the current rate.

Note : The above story is based on materials provided by Columbia University

Study finds order in the apparent randomness of Earth’s evolving landscape

Stanford Earth scientists have created tools to analyze branched networks of Earth-bound channels formed by water and erosion. The work could provide insights into processes that form branched networks like those on the surface of Mars (left) and Titan (center) and in the human circulatory system. Credit: Images courtesy of NASA/JPL and Wikimedia Commons

As we all know, water runs downhill, forming channels and branched networks as it flows. It’s been that way forever. But, believe it or not, scientists’ understanding of these networks hasn’t changed much in the last century. Even modern techniques developed and employed since the 1960s cannot easily distinguish between channel networks generated randomly inside a computer and images of channels formed in the real world.
But work by Stanford School of Earth Sciences recent PhD recipient Eitan Shelef and George Hilley, an associate professor of geological and environmental sciences, is beginning to shed light on this fundamental problem, and the tools they created might shine light on not just Earth-bound channels but also those on Mars and even in the human circulatory system.

Shelef’s work, recently published in Geophysical Research Letters, challenges 50 years of research built on the assumption that the geometry of channel networks reflected a mathematically random process. Shelef and Hilley developed powerful mathematical relationships that captured not just the geometry of hillside channels but the geometry of the underlying landscape as well.

Shelef, now a postdoctoral scholar at Los Alamos National Laboratory, explained that in these equations, the researchers found a simple metric that distinguishes natural channel networks from those formed randomly within a computer, and in doing so, they firmly rejected the mathematically random hypothesis posed in the 1960s.

In rejecting this decades-old hypothesis, Shelef and Hilley can now extract invaluable three-dimensional data from two-dimensional images.

“The way in which branched networks were measured in the past relied only on the two-dimensional map patterns of the channels in the networks,” said Hilley, a leading researcher on landscape evolution.

Using high-resolution images captured with laser altimetry, the pair analyzed not only the channels but the ridgelines as well.

By incorporating information about the ridgelines separating the channels, Shelef and Hilley related channel network geometry to the two-dimensional signature left by three-dimensional erosion. Because different erosional processes leave different erosional signatures, which in turn affect channel patterns, Shelef and Hilley’s approach allows Earth scientists to infer the processes that erode the landscape simply by analyzing the overlying channel network.

Shelef expanded on this, pointing out that his mathematical tools can help decipher the processes that shape channel networks in areas in which scientists have good imagery but limited elevation data, such as channel networks now buried underground, or channel networks on Mars or Saturn’s largest moon, Titan.

For example, images from NASA’s Mars Reconnaissance Orbiter showed branched channel networks etched into the red planet’s surface. Images beamed back from the Huygens spacecraft as it landed on Titan also showed channels likely formed from flowing liquid methane. Shelef’s research could help scientists better understand the processes acting on Titan today and the processes that carved out channel networks on Mars millions, if not billions, of years ago.

“Channel networks are one of the most common and ubiquitous geometric forms found on the surface of this and some other planets,” Hilley said.

The pair’s analysis of branched networks needn’t be limited to flowing liquids. Branched networks appear in life sciences as well, found in tree leaves and even the human circulatory system. With such ubiquity of branched networks, Shelef’s Earth science research might reach across disciplines. Understanding the processes that form branched biological networks could provide valuable scientific insights.

By seeing past the randomness inferred from previous research, Shelef and Hilley can better understand the processes that shape the world around us.

More information:
‘Symmetry, randomness and process in the structure of branched channel networks,’ Geophysical Research Letters (DOI: 10.1002/2014GL059816)

Note : The above story is based on materials provided by Stanford University

Pyrope

©Parent Géry

Chemical Formula: Mg3Al2(SiO4)3
Locality: Zoblitz, Germany.
Name Origin: From the Greek, pyropos, “fiery-eyed” in allusion to the red hue.

The mineral pyrope is a member of the garnet group. Pyrope is the only member of the garnet family to always display red colouration in natural samples, and it is from this characteristic that it gets its name: from the Greek for fire and eye. Despite being less common than most garnets, it is a widely used gemstone with numerous alternative names, some of which are misnomers. Chrome pyrope, and Bohemian garnet are two alternative names, the usage of the latter being discouraged by the Gemological Institute of America.Misnomers include Colorado ruby, Arizona ruby, California ruby, Rocky Mountain ruby, Elie Ruby, Bohemian carbuncle, and Cape ruby.

The composition of pure pyrope is Mg3Al2(SiO4)3, although typically other elements are present in at least minor proportions—these other elements include Ca, Cr, Fe and Mn. Pyrope forms a solid solution series with almandine and spessartine, which are collectively known as the pyralspite garnets (pyrope, almandine, spessartine). Iron and manganese substitute for the magnesium in the pyrope structure. The resultant, mixed composition garnets are defined according to their pyrope-almandine ratio. The semi-precious stone rhodolite is a garnet of ~70% pyrope composition.

The origin of most pyrope is in ultramafic rocks, typically peridotite from the Earth’s mantle: these mantle-derived peridotites can be attributed both to igneous and metamorphic processes. Pyrope also occurs in ultrahigh-pressure (UHP) metamorphic rocks, as in the Dora-Maira massif in the western Alps. In that massif, nearly pure pyrope occurs in crystals to almost 12 cm in diameter; some of that pyrope has inclusions of coesite, and some has inclusions of enstatite and sapphirine.

Pyrope is common in peridotite xenoliths from kimberlite pipes, some of which are diamond-bearing. Pyrope found in association with diamond commonly has a Cr2O3 content of 3-8%, which imparts a distinctive violet to deep purple colouration (often with a greenish tinge) and because of this is often used as a kimberlite indicator mineral in areas where erosive activity makes pin pointing the origin of the pipe difficult. These varieties are known as chrome-pyrope, or G9/G10 garnets.

History

Authors: WERNER
Discovery date: 1803
Town of Origin : LNS
Country of Origin : TCHECOSLOVAQUIE

Chemical properties

Chemical Class : NESOSILICATES
Subclass : Neosilicates
Group : GRENATS
Chemical Formula : Mg3Al2(SiO4)3
Impurities: Fe;Mn;Ca

Optical properties

Optical and misc. Properties : Transparent  –   Translucide  –   Fragile, cassant  –   Gemme, pierre fine
Refractive Index : 1,71

Physical properties

Morphology : DODECAEDRIQUE; TRAPEZOEDRIQUE; GRENU; MASSIF; GALET; GRAIN
Hardness: from 7,00 to 7,50
Density: 3,58
Color : pinkish red; violet red; orange red; black; purplish red; red; black red
Luster: vitreous; resinous
Streak: white
Break: conchoidal
Cleavage : NO

Photos:

Locality: Sunset Crater, Arizona, USA Source: Marcus Origlieri Owner: RRUFF
Pyrope Garnet Weight: 2.18 ct Exact Size: 8.02 mm x 4.51 mm © GemSelect
Pyrope Location: Governador Valadares, Rio Doce, Minas Gerais, Southeast Region, Brazil. Scale:     6x6x6 mm. Copyright: © John Betts – Fine Minerals

Pressure cell for reproducing deep-Earth chemistry

A new pressure cell invented by UC Davis researchers makes it possible to simulate chemical reactions deep in the Earth’s crust. Credit: Image courtesy of University of California – Davis

A new pressure cell invented by UC Davis researchers makes it possible to simulate chemical reactions deep in the Earth’s crust. The cell allows researchers to perform nuclear magnetic resonance (NMR) measurements on as little as 10 microliters of liquid at pressures up to 20 kiloBar.
“NMR is our window into the chemical world,” said Brent Pautler, a postdoctoral researcher in chemistry at UC Davis and first author on the paper published July 2 in the online edition of the journal Angewandte Chemie. “It lets us see chemical reactions as they are happening.”

The new device allows researchers for the first time to study chemical reactions in liquid water under pressure, without it freezing into a solid.

“We were able to get to the point where we could no longer ignore the compressibility of the water molecules,” Pautler said. “This is the first time this has ever been reported.”

Geochemists want to know what kind of chemistry is happening deep in the Earth’s crust, beyond the reach of boreholes. These chemical reactions could affect water and minerals that eventually migrate to the surface, or the behavior of carbon cycling between the Earth’s depths and the surface.

“Aqueous fluids deep in the Earth are the great unknown for geochemists,” said Chris Colla, a graduate student in Earth & Physical Sciences at UC Davis and co-author on the paper. “By doing NMR we can get an inside view of what is occurring deep in the Earth’s crust.”

For example, Pautler, Colla and colleagues have already looked at calcium ions in solution. Dissolved calcium ions can be surrounded by four, six or eight water molecules. High pressure forces dissolved calcium into an eight-water state, they found.

The high-pressure measurements could also shed light on chemical processes involved in hydraulic fracturing, or “fracking,” and the behavior of buried nuclear waste over long periods of time. Fracking is the process of extracting oil and gas by injecting liquids under high pressure into rocks.

The high-pressure NMR cell was built in the machine shop at the Crocker Nuclear Laboratory with the help of Peter Klavins, research specialist in the Department of Physics, and Steve Harley, a former UC Davis graduate student now at the Lawrence Livermore National Laboratory.

Other coauthors on the paper are, at UC Davis: Prof. William Casey and Rene Johnson, Department of Chemistry; Jeffrey Walton, NMR Facility; André Ohlin, at Monash University, Australia and Dimitri Sverjensky at Johns Hopkins University and the Carnegie Institution of New York. The work was supported by the U.S. Department of Energy.

Video :

Note : The above story is based on materials provided by University of California – Davis.

New study of largely unstudied mesophotic coral reef geology

Researcher David Weinstein recovers experimental coral substrates for bioerosion study at mid-patch reef site. Credit: Photo by Rick Gomez, UM Rosenstiel School Diving Safety Officer

Researchers compare bioerosion on deeper reef systems to better understand long-term structural sustainability

MIAMI – A new study on biological erosion of mesophotic tropical coral reefs, which are low energy reef environments between 30-150 meters deep, provides new insights into processes that affect the overall structure of these important ecosystems. The purpose of the study was to better understand how bioerosion rates and distribution of bioeroding organisms, such as fish, mollusks and sponges, differ between mesophotic reefs and their shallow-water counterparts and the implications of those variations on the sustainability of the reef structure.

Due to major advancements in deeper underwater diving technology, a large renewal of interest in mesophotic reefs has pulsed through the scientific community because of their high biodiversity, vast extent, and potential refuge for shallower water reef species at risk from the impacts of climate change.

“Studying how mesophotic reefs function and thrive is especially critical now, when considering results from the new IPCC report reviewed by over 1700 expects said that coral reefs are the most vulnerable marine ecosystems on Earth to the adverse effects of climate change,” said David Weinstein, Rosenstiel School Ph.D. student and lead author of the study. “Developing effective environmental management strategies for these important reef systems requires a basic fundamental understanding of the underlining architecture that supports and creates diverse biological ecosystems.”

Weinstein and his research team used previously identified mesophotic reefs at 30-50 meters deep located in the U.S. Virgin Islands composed of a surprising number of coral growing on top different types of reef structures (patches, linear banks, basins) to better understand the role sedimentary processes have in creating and maintaining so many different structures that are critical for maximizing the biodiversity and health of the ecosystem. Researchers analyzed coral rubble and coral skeleton discs collected after one and two years of exposure to determine the sources and rates of bioerosion at these reefs.

Results of the study found that the architecturally unique structures in the study area experience significantly different bioerosion rates.

“This has very important implications when trying to predict how these reefs will grow over time and where preservation efforts might be most effective,” said Weinstein.

Although erosion of the coral skeleton disks at the very deepest sites was more uniform, the researchers suggest that this is likely because the substrates used in the study were all of uniform composition, unlike the diverse composition of the sites. These results imply that bioerosional processes at these depths still exaggerate differences in reef structure depending on the amount of living and dead coral at each reef, the amount of time that material is exposed on the surface, and different localized current flows experienced.

The study also confirmed important concepts in coral geology research that lacked proof from studies venturing deeper than 35 meters. Coral reef bioerosion in the U.S. Virgin Islands and potentially in most of the Caribbean does generally decreases with depth. This result stems from the finding that parrotfish are now the most significant bioeroding group from shallow reefs down to a mesophotic reef transition zone identified by Weinstein at 30-35 meters in depth. The study also was able to conclude bioeroding sponges are the primary organisms responsible for long-term structural modification of mesophotic reefs beyond the transitional zone.

“Coral reefs are essentially a thin benthos veneer draped upon a biologically produced inorganic three-dimensional foundation that creates habitats for many marine organisms,” said Weinstein. “Since mesophotic reefs grow so much slower than shallower reefs, identifying the sources and rate of erosion on mesophotic reefs is even more important to understand the long-term structural sustainability of these tropical reefs systems.”

However, Weinstein suggests that other processes, such as coral growth rates and cementation, must also be more fully studied before scientists have a complete understanding of mesophotic coral reefs.

The paper, currently available online and scheduled for print in a special coral reef edition of the journal Geomorphology later this summer is one of the first to address mesophotic reef sedimentology.

More information, videos, pictures, and new developments can be found at: http://www.rsmas.miami.edu/users/dweinstein/

Note : The above story is based on materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science

Pyromorphite

Pyromorphite from Broken Hill, New South Wales, Australia. Photograph taken at the Natural History Museum, London. © Aram Dulyan

Chemical Formula: Pb5(PO4)3Cl
Name Origin: From the Greek pyr – “fire” and morfe – “form” in allusion the recrystallization reaction of the molten mineral.

Pyromorphite is a mineral species composed of lead chlorophosphate: Pb5(PO4)3Cl, sometimes occurring in sufficient abundance to be mined as an ore of lead. Crystals are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. It is part of a series with two other minerals: mimetite (Pb5(AsO4)3Cl) and vanadinite (Pb5(VO4)3Cl), the resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests.

They were formerly confused under the names green lead ore and brown lead ore (German: Grünbleierz and Braunbleierz). The phosphate was first distinguished chemically by M. H. Klaproth in 1784, and it was named pyromorphite by J. F. L. Hausmann in 1813. The name is derived from the Greek for pyr (fire) and morfe (form) due to its crystallization behavior after being melted.

History

Authors : HAUSMANN
Discovery date : 1813

Optical properties

Optical and misc. Properties : Transparent  –   Translucide  –   Fragile, cassant  –   Luminescent, fluorescent
Refractive Index : from 2,04 to 2,05

Physical properties

Hardness: from 3,50 to 4,00
Density : 7,04
Color : green; yellow; orange; brown; grey; colorless; white; red yellow; yellowish brown; purplish brown
Luster: sub-adamantine; resinous; greasy
Streak : white; grey; yellowish
Break: irregular; sub-conchoidal
Cleavage: yes

Photos:

Pyromorphite Mina San Andrés, Geoda Realces, Villaviciosa de Córdoba, Espiel, Córdoba  Spain (10/11-1997) Specimen size: 3.7 × 2.5 × 1 cm = 1.5” × 1.0” × 0.4” Main crystal size: 0.3 × 0.3 cm = 0.1” × 0.1” © Fabre Minerals
Pyromorphite Rosenberg Mine, Braubach, Bad Ems District, Lahn valley, Rhineland-Palatinate, Germany Size: 6.0 x 2.5 x 1.6 cm (miniature) © danweinrich
Pyromorphite Mine des Farges, Ussel, Corrèze  France Specimen size: 3 × 2.5 × 1.4 cm = 1.2” × 1.0” × 0.6” © Fabre Minerals
Pyromorphite Bunker Hill Mine, Kellogg, Coeur d’Alene District, Shoshone Co., Idaho, USA Size: 2.0 x 2.0 x 1.2 cm (thumbnail) © danweinrich

Evidence of super-fast deep earthquake

The supershear 2013 Sea of Okhotsk earthquake had similar magnitude and fault geometry as the damaging 1994 Northridge earthquake in California, but a much larger depth and faster rupture speed. The high rupture speed (approximately 8 kilometers per second, or 18,000 miles per hour) away from the hypocenter, shown as the red star, concentrates strong shaking on the “Mach front.” Credit: Image courtesy of University of California – San Diego

As scientists learn more about earthquakes that rupture at fault zones near the planet’s surface — and the mechanisms that trigger them — an even more intriguing earthquake mystery lies deeper in the planet.
Scientists at Scripps Institution of Oceanography at UC San Diego have discovered the first evidence that deep earthquakes, those breaking at more than 400 kilometers (250 miles) below Earth’s surface, can rupture much faster than ordinary earthquakes. The finding gives seismologists new clues about the forces behind deep earthquakes as well as fast-breaking earthquakes that strike near the surface.

Seismologists have documented a handful of these events, in which an earthquake’s rupture travels faster than the shear waves of seismic energy that it radiates. These “supershear” earthquakes have rupture speeds of four kilometers per second (an astonishing 9,000 miles per hour) or more.

In a National Science Foundation-funded study reported in the June 11, 2014, issue of the journal Science, Scripps geophysicists Zhongwen Zhan and Peter Shearer of Scripps, along with their colleagues at Caltech, discovered the first deep supershear earthquake while examining the aftershocks of a magnitude 8.3 earthquake on May 24, 2013, in the Sea of Okhotsk off the Russian mainland.

Details of a magnitude 6.7 aftershock of the event captured Zhan’s attention. Analyzing data from the IRIS (Incorporated Research Institutions for Seismology) consortium, which coordinates a global network of seismological instruments, Zhan noted that most seismometers around the world yielded similar records, all suggesting an anomalously short duration for a magnitude 6.7 earthquake.

Data from one seismometer, however, stationed closest to the event in Russia’s Kamchatka Peninsula, told a different story with intriguing details.

After closely analyzing the data, Zhan not only found that the aftershock ruptured extremely deeply at 640 kilometers (400 miles) below Earth’s surface, but its rupture velocity was extraordinary — about eight kilometers per second (five miles per second), nearly 50 percent faster than the shear wave velocity at that depth.

“For a 6.7 earthquake you would expect a duration of seven to eight seconds, but this one lasted just two seconds,” said Shearer, a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps. “This is the first definitive example of supershear rupture for a deep earthquake since previously supershear ruptures have been documented only for shallow earthquakes.”

“This finding will help us understand why deep earthquakes happen,” said Zhan. “One quarter of earthquakes occur at large depths, and some of these can be pretty big, but we still don’t understand why they happen. So this earthquake provides a new observation for deep earthquakes and high-rupture speeds.”

Zhan also believes the new information will be useful in examining ultra-fast earthquakes and their potential for impacting fault zones near Earth’s surface. Although not of supershear caliber, California’s destructive 1994 Northridge earthquake had a comparable size and geometry to that of the 6.7 Sea of Okhotsk aftershock.

“If a shallow earthquake such as Northridge goes supershear, it could cause even more shaking and possibly more damage,” said Zhan.

Note : The above story is based on materials provided by University of California – San Diego. The original article was written by Mario Aguilera.

NASA spacecraft observes further evidence of dry ice gullies on Mars

This pair of before (left) and after (right) images from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter documents formation of a new channel on a Martian slope between 2010 and 2013, likely resulting from activity of carbon-dioxide frost. Credit: NASA/JPL-Caltech/Univ. of Arizona

Repeated high-resolution observations made by NASA’s Mars Reconnaissance Orbiter (MRO) indicate the gullies on Mars’ surface are primarily formed by the seasonal freezing of carbon dioxide, not liquid water.

The first reports of formative gullies on Mars in 2000 generated excitement and headlines because they suggested the presence of liquid water on the Red Planet, the eroding action of which forms gullies here on Earth. Mars has water vapor and plenty of frozen water, but the presence of liquid water on the neighboring planet, a necessity for all known life, has not been confirmed. This latest report about gullies has been posted online by the journal Icarus.

“As recently as five years ago, I thought the gullies on Mars indicated activity of liquid water,” said lead author Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Flagstaff, Arizona. “We were able to get many more observations, and as we started to see more activity and pin down the timing of gully formation and change, we saw that the activity occurs in winter.”

Dundas and collaborators used the High Resolution Imaging Science Experiment (HiRISE) camera on MRO to examine gullies at 356 sites on Mars, beginning in 2006. Thirty-eight of the sites showed active gully formation, such as new channel segments and increased deposits at the downhill end of some gullies.

Using dated before-and-after images, researchers determined the timing of this activity coincided with seasonal carbon-dioxide frost and temperatures that would not have allowed for liquid water.

Frozen carbon dioxide, commonly called dry ice, does not exist naturally on Earth, but is plentiful on Mars. It has been linked to active processes on Mars such as carbon dioxide gas geysers and lines on sand dunes plowed by blocks of dry ice. One mechanism by which carbon-dioxide frost might drive gully flows is by gas that is sublimating from the frost providing lubrication for dry material to flow. Another may be slides due to the accumulating weight of seasonal frost buildup on steep slopes.

The findings in this latest report suggest all of the fresh-appearing gullies seen on Mars can be attributed to processes currently underway, whereas earlier hypotheses suggested they formed thousands to millions of years ago when climate conditions were possibly conducive to liquid water on Mars.

Dundas’s co-authors on the new report are Serina Diniega of NASA’s Jet Propulsion Laboratory in Pasadena, California, and Alfred McEwen of the University of Arizona, Tucson.

“Much of the information we have about gully formation, and other active processes, comes from the longevity of MRO and other orbiters,” said Diniega. “This allows us to make repeated observations of sites to examine surface changes over time.”

Although the findings about gullies point to processes that do not involve liquid water, possible action by liquid water on Mars has been reported in the past year in other findings from the HiRISE team. Those observations were of a smaller type of surface-flow feature.

An upcoming special issue of Icarus will include multiple reports about active processes on Mars, including smaller flows that are strong indications of the presence of liquid water on Mars today.

“I like that Mars can still surprise us,” Dundas said. “Martian gullies are fascinating features that allow us to investigate a process we just don’t see on Earth.”

HiRISE is operated by the University of Arizona, Tucson. The instrument was built by Ball Aerospace & Technologies Corp. of Boulder, Colorado. The Mars Reconnaissance Orbiter Project is managed for NASA’s Science Mission Directorate in Washington, by JPL, a division of the California Institute of Technology, Pasadena.

For more information about HiRISE, visit: http://hirise.lpl.arizona.edu

Additional information about MRO is online at: http://www.nasa.gov/mro

For recent findings suggesting the presence of liquid water on Mars, visit: http://go.nasa.gov/1q1VRLS

Note : The above story is based on materials provided by NASA/Jet Propulsion Laboratory.

Pyrolusite

Pyrolusite Dona Ana County, New Mexico, USA Miniature, 5.5 x 2.0 x 1.6 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”

Chemical Formula: MnO2
Name Origin: From the Greek, pyro and louein, “fire” and “to wash,” because it was used to remove the greenish color imparted to glass by iron compounds.

Pyrolusite is a mineral consisting essentially of manganese dioxide (MnO2) and is important as an ore of manganese. It is a black, amorphous appearing mineral, often with a granular, fibrous or columnar structure, sometimes forming reniform crusts. It has a metallic luster, a black or bluish-black streak, and readily soils the fingers. The specific gravity is about 4.8. Its name is from the Greek for fire and to wash, in reference to its use as a way to remove tints from glass.

History

Authors : HAIDINGER
Discovery date : 1827

Optical properties

Optical and misc. Properties : Fragile, cassant  –   Opaque  –   Macles possibles  –
Reflective Power: HAUT

Physical Properties

Hardness: from 6,00 to 6,50
Density : 5,06
Color : steel grey; black
Luster: metallic; unpolished
Streak : black; bluish black
Cleavage : yes

Photos:

Pyrolusite Ilfeld, Harz Mts., Germany Small Cabinet, 7.7 x 6.3 x 2.7 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Pyrolusite Dona Ana County, New Mexico, USA Small Cabinet, 6.5 x 3.2 x 1.7 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Locality: Unnamed prospect, Tal-Tal, Antofagasta Region, Chile Source: Bob Jenkins Owner: RRUFF
Macro of a pyrolusite mineral with dendrite crystal formations. It is approximately 3 ½ inches (9 cm) tall. © Jonathan Zander

Birdlike fossil challenges notion that birds evolved from ground-dwelling dinosaurs

This is a skeletal reconstruction of Scansoriopteryx with outlines to indicate the extent of the feathers. Credit: Stephen A. Czerkas

The re-examination of a sparrow-sized fossil from China challenges the commonly held belief that birds evolved from ground-dwelling theropod dinosaurs that gained the ability to fly. The birdlike fossil is actually not a dinosaur, as previously thought, but much rather the remains of a tiny tree-climbing animal that could glide, say American researchers Stephen Czerkas of the Dinosaur Museum in Blanding, Utah, and Alan Feduccia of the University of North Carolina. The study appears in Springer’s Journal of Ornithology.

The fossil of the Scansoriopteryx (which means “climbing wing”) was found in Inner Mongolia, and is part of an ongoing cooperative study with the Chinese Academy of Geological Sciences. It was previously classified as a coelurosaurian theropod dinosaur, from which many experts believe flying dinosaurs and later birds evolved. The research duo used advanced 3D microscopy, high resolution photography and low angle lighting to reveal structures not clearly visible before. These techniques made it possible to interpret the natural contours of the bones. Many ambiguous aspects of the fossil’s pelvis, forelimbs, hind limbs, and tail were confirmed, while it was discovered that it had elongated tendons along its tail vertebrae similar to Velociraptor.

Czerkas and Feduccia say that Scansoriopteryx unequivocally lacks the fundamental structural skeletal features to classify it as a dinosaur. They also believe that dinosaurs are not the primitive ancestors of birds. The Scansoriopteryx should rather be seen as an early bird whose ancestors are to be found among tree-climbing archosaurs that lived in a time well before dinosaurs.

Through their investigations, the researchers found a combination of plesiomorphic or ancestral non-dinosaurian traits along with highly derived features. It has numerous unambiguous birdlike features such as elongated forelimbs, wing and hind limb feathers, wing membranes in front of its elbow, half-moon shaped wrist-like bones, bird-like perching feet, a tail with short anterior vertebrae, and claws that make tree climbing possible. The researchers specifically note the primitive elongated feathers on the forelimbs and hind limbs. This suggests that Scansoriopteryx is a basal or ancestral form of early birds that had mastered the basic aerodynamic maneuvers of parachuting or gliding from trees.

Their findings validate predictions first made in the early 1900’s that the ancestors of birds were small, tree-dwelling archosaurs which enhanced their incipient ability to fly with feathers that enabled them to at least glide. This “trees down” view is in contrast with the “ground up” view embraced by many palaeontologists in recent decades that birds derived from terrestrial theropod dinosaurs.

“The identification of Scansoriopteryx as a non-dinosaurian bird enables a reevaluation in the understanding of the relationship between dinosaurs and birds. Scientists finally have the key to unlock the doors that separate dinosaurs from birds,” explained Czerkas.

Feduccia added, “Instead of regarding birds as deriving from dinosaurs, Scansoriopteryx reinstates the validity of regarding them as a separate class uniquely avian and non-dinosaurian.”

Note : The above story is based on materials provided by Springer.

1...272273274...333Page 273 of 333

Related Articles

All
Facebook Instagram Linkedin TikTok Twitter Youtube
© © 2011-2024. All Rights Reserved.