Scientists at the University of Liverpool have shown that deep sea fault zones could transport much larger amounts of water from the Earth’s oceans to the upper mantle than previously thought.
Water is carried mantle by deep sea fault zones which penetrate the oceanic plate as it bends into the subduction zone. Subduction, where an oceanic tectonic plate is forced beneath another plate, causes large earthquakes such as the recent Tohoku earthquake, as well as many earthquakes that occur hundreds of kilometers below the Earth’s surface.
Seismic modelling
Seismologists at Liverpool have estimated that over the age of the Earth, the Japan subduction zone alone could transport the equivalent of up to three and a half times the water of all the Earth’s oceans to its mantle.
Using seismic modelling techniques the researchers analysed earthquakes which occurred more than 100 km below the Earth’s surface in the Wadati-Benioff zone, a plane of Earthquakes that occur in the oceanic plate as it sinks deep into the mantle.
Analysis of the seismic waves from these earthquakes shows that they occurred on 1 – 2 km wide fault zones with low seismic velocities. Seismic waves travel slower in these fault zones than in the rest of the subducting plate because the sea water that percolated through the faults reacted with the oceanic rocks to form serpentinite – a mineral that contains water.
Some of the water carried to the mantle by these hydrated fault zones is released as the tectonic plate heats up. This water causes the mantle material to melt, causing volcanoes above the subduction zone such as those that form the Pacific ‘ring of fire’. Some water is transported deeper into the mantle, and is stored in the deep Earth.
“It has been known for a long time that subducting plates carry oceanic water to the mantle,” said Tom Garth, a PhD student in the Earthquake Seismology research group led by Professor Andreas Rietbrock.
“This water causes melting in the mantle, which leads to arc releasing some of the water back into the atmosphere. Part of the subducted water however is carried deeper into the mantle and may be stored there.
Large amounts of water deep in the Earth
“We found that fault zones that form in the deep oceanic trench offshore Northern Japan persist to depths of up to 150 km. These hydrated fault zones can carry large amounts of water, suggesting that subduction zones carry much more water from the ocean down to the mantle than has previously been suggested.
“This supports the theory that there are large amounts of water stored deep in the Earth.”
Understanding how much water is delivered to the mantle contributes to knowledge of how the mantle convects, and how it melts, which helps to understand how plate tectonics began, and how the continental crust was formed.
Note : The above story is based on materials provided by University of Liverpool
New research, published in Earth and Planetary Research Letters, led by scientists from the University of Cambridge, used plankton – tiny bugs, whose shells litter the ocean floors. By drilling into the seabed scientists can extract shells from plankton which lived millions of years ago.
‘The shells we used are of a type of plankton called foraminifera. They’re only about one tenth of a millimetre big, or small rather, and have been around over 150 million years, so we get a really well-preserved record of them in marine sediments going back tens of millions of years,’ explains Oscar Branson, a PhD student at the University of Cambridge and lead author of the study. ‘Recently people have been analysing them for climate records, but now we realise they’re more complex.’
As plankton grow they build a bit more onto their shells every day by turning elements in the sea water into harder minerals and adding them on. The impurities in the shell depend on what was in the sea water as the plankton grew, so these million-year-old shells can give us an almost daily snapshot of the chemistry of the oceans as it was when they were still alive.
‘We realised plankton have these growth bands, like tree rings, which we thought might tell us something in more detail. It turns out these bands are produced almost daily so you may one day be able to get a 5 day weather report by looking at them,’ Branson says.
The team used a synchrotron in California to study the shells, which let them find out how much magnesium was in each growth band compared to other chemicals.
Synchrotrons use magnetic and electrical fields to accelerate particles round a huge ring. As these charged particles approach the speed of light they give off radiation known as synchrotron light.
Researchers divert this light away from the main ring and down a targeted beamline, where it can be used in a similar way to an X-ray to study the structure of matter at tiny scales.
‘The concentration of magnesium changes depending on temperature of sea water, so by finding out how much there was in the shell it should allow us to find out the temperature of seawater virtually each day for the last 150 million years,’ says Branson.
The magnesium is more likely to be built into shells in warmer waters because it replaces calcium in their atomic structure.
‘Our X-ray data show that the trace magnesium sits inside the crystalline mineral structure of the plankton shell,’ concludes Professor Simon Redfern of the University of Cambridge, who also worked on the project. ‘That’s important because it validates previous assumptions about using magnesium contents as a measure of past ocean temperature.’
Note : The above story is based on materials provided by PlanetEarth Online
Chemical Formula: Cu9S5 Locality: In the USA, at Butte, Silver Bow Co., Montana. Name Origin: From the Greek for “two kinds” or “sexes,” in reference to the presumed presence of both cuprous and cupric ions.
Digenite is a copper sulfide mineral with formula: Cu9S5. Digenite is a black to dark blue opaque mineral that crystallizes with a trigonal – hexagonal scalenohedral structure. In habit it is usually massive, but does often show pseudo-cubic forms. It has poor to indistinct cleavage and a brittle fracture. It has a Mohs hardness of 2.5 to 3 and a specific gravity of 5.6. It is found in copper sulfide deposits of both primary and supergene occurrences. It is typically associated with and often intergrown with chalcocite, covellite, djurleite, bornite, chalcopyrite and pyrite. The type locality is Sangerhausen, Thuringia, Germany, in copper slate deposits.
Occurrence
Digenite occurs in the transitional zone of supergene oxidation of primary sulfide ore deposits, at the interface between the upper and lower saprolite ore zones. It is rarely an important mineral for copper ores, as it is more usually replaced by chalcocite further up in the weathering profile, and is a minor weathering product of primary chalcopyrite. Natural digenite always contains a small amount of iron and is considered to be stable only in the Cu-Fe-S system.
In the Deflector and Deflector West Cu-Au lode deposits of the Gullewa Greenstone Belt, Western Australia, digenite is an important constituent of the transitional Cu-Au ore. However, it is difficult to treat metallurgically and remains a refractory ore type. In this locality digenite is found with covellite, chalcocite and bornite.
It was first described in 1844 from the type locality of Sangerhausen, Saxony-Anhalt, Germany. The name is from the Greek digenus meaning of two origins in reference to its close resemblance with chalcocite and covellite.
Physical Properties of Digenite
Cleavage: {???} Indistinct Color: Blue, Dark blue, Black. Density: 5.6 Diaphaneity: Opaque Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 2.5-3 – Finger Nail-Calcite Luster: Sub Metallic Streak: grayish black
Yenisei (Russian: Енисе́й), also written as Yenisey, is the largest river system flowing to the Arctic Ocean. It is the central of the three great Siberian rivers that flow into the Arctic Ocean (the other two being the Ob River and the Lena River). Rising in Mongolia, it follows a northerly course to the Yenisei Gulf in the Kara Sea, draining a large part of central Siberia, the longest stream following the Yenisei-Angara-Selenga-Ider river system.
The upper reaches, subject to rapids and flooding, pass through sparsely populated areas. The middle section is controlled by a series of massive hydroelectric dams fuelling significant Russian primary industry. Partly built by gulag labor in Soviet times, industrial contamination remains a serious problem in an area hard to police. Moving on through sparsely populated taiga, the Yenisei swells with numerous tributaries and finally reaches the Kara Sea in desolate tundra where it is icebound for more than half the year.
The maximum depth of the Yenisei River is 80 feet (24 m) and the average depth is 45 feet (14 m). The depth of river outflow is 106 feet (32 m) and inflow is 101 feet (31 m).
The Yenisei basin, including Lake Baikal
Course
The river flows through Khakassia.
Lake Baikal
The 320 km (200 mi) partly navigable Upper Angara River feeds into the northern end of Lake Baikal from the Buryat Republic but the largest inflow is from the Selenga which forms a delta on the south-eastern side.
Lower Yenisei
The Great Kaz joins the Yenisei 300 kilometres (190 mi) downstream from Strelka. It is noteworthy for its connection to the Ob via the Ob-Yenisei canal and the Ket River.
Note : The above story is based on materials provided by Wikipedia
The work is expected to help discover new mineral deposits in WA, but the technique isn’t just limited to mining. Credit: Paul Reid
Mark Jessell has travelled half way around the world to help develop 3D software technology that will allow us to scratch beneath the earth’s surface and tell us more about such things as our mineral and water resources.
Professor Jessell is an internationally renowned structural geologist who recently moved to Perth to take up one of three prestigious WA Research Fellowships.
He is now based at the Centre for Exploration Targeting at the University of Western Australia.
He says good data is the key to unlocking the earth’s secrets.
“One of the problems is that we don’t have enough data,” he says.
“Even though we have lots of data, it’s not enough.
“We can a have a photograph of the surface, but what’s going on beneath the surface is much less sure.
“One of the problems we have is that the software at the moment isn’t really adapted to take in that uncertainty.”
As part of his research over the next few years, Prof Jessell will be looking at modifying and re-writing existing 3D software to tweak it to WA conditions.
“What we’re going to try to do is develop things that sit on top of existing packages that are specifically aimed at solving our problems,” he says.
Part of the work will focus on what is called geological inversion, which involves using geophysical data in 3D models and showing what is under the earth’s surface.
It is innovative technology – and the high-powered computing facilities such as those at the recently-opened Pawsey Centre was one of the things that attracted him to Perth.
“For the geophysical inversion side of our project, the access to that supercomputing facility is a big draw[card],” he says.
The work is expected to help discover new mineral deposits in WA, but the technique isn’t just limited to mining.
“The 3D geology of Western Australia is important to lots of other groups apart from the minerals industry,” he says.
“It’s also important to anybody who is worried about water in WA because the water we have comes from beneath the surface.
“And where it’s stored and where it goes and how it interacts with runoff from agriculture is all controlled by the 3D distribution of the geology.
“This is a big topic and its not something we’re going to be able to do alone.
“I’ve got colleagues at the CSIRO and the Geological Survey of WA and what we hope to do is have a critical mass of people working together on this problem.”
Note : The above story is based on materials provided by Science Network WA
Locality: Common world wide. Name Origin: From the Greek word “to scatter,” referring to the mineral’s easy disintegration in the blowpipe flame.
Diaspore also known as empholite, kayserite, or tanatarite, is an aluminium oxide hydroxide mineral, α-AlO(OH), crystallizing in the orthorhombic system and isomorphous with goethite. It occurs sometimes as flattened crystals, but usually as lamellar or scaly masses, the flattened surface being a direction of perfect cleavage on which the lustre is markedly pearly in character. It is colorless or greyish-white, yellowish, sometimes violet in color, and varies from translucent to transparent. It may be readily distinguished from other colorless transparent minerals with a perfect cleavage and pearly luster—like mica, talc, brucite, and gypsum— by its greater hardness of 6.5 – 7. The specific gravity is 3.4. When heated before the blowpipe it decrepitates violently, breaking up into white pearly scales.
The mineral occurs as an alteration product of corundum or emery and is found in granular limestone and other crystalline rocks. Well-developed crystals are found in the emery deposits of the Urals and at Chester, Massachusetts, and in kaolin at Schemnitz in Hungary. If obtainable in large quantity, it would be of economic importance as a source of aluminium.
Diaspore, along with gibbsite and boehmite, is a major component of the aluminium ore bauxite.
It was first described in 1801 for an occurrence in Mramorsk Zavod, Sverdlovskaya Oblast, Middle Urals, Russia. The name is from the Greek for διασπείρειυ, to scatter, in allusion to its decrepitation on heating.
Ottomanite, and zultanite are trade names for gem-quality diaspore (also known as Turkish diaspore) from the İlbir Mountains of southwest Turkey.
Physical Properties of Diaspore
Cleavage: {010} Perfect, {110} Good Color: White, Greenish gray, Grayish brown, Colorless, Yellow. Density: 3.3 – 3.5, Average = 3.4 Diaphaneity: Transparent to subtranslucent Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 6.5-7 – Pyrite-Quartz Luminescence: Non-fluorescent. Luster: Vitreous – Pearly Streak: white
Photos :
This sample of diaspore is displayed in the Smithsonian Museum of Natural History. The sample is about 3 cm across and is from Mugla, Menderes Mountains, Anatolia, Turkey.DIASPORE on MARGARITEMugla Province, Aegean Region, Turkey Miniature, 3.8 x 2.6 x 2.3 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
At roughly 50-60 feet long, the Yongjinglong individual discovered was a medium-sized Titanosaur. Anatomical evidence, however, points to it being a juvenile; adults may have been larger.Credit: University of Pennsylvania
A team led by University of Pennsylvania paleontologists has characterized a new dinosaur based on fossil remains found in northwestern China. The species, a plant-eating sauropod named Yongjinglong datangi, roamed during the Early Cretaceous period, more than 100 million years ago. This sauropod belonged to a group known as Titanosauria, members of which were among the largest living creatures to ever walk the earth.
At roughly 50-60 feet long, the Yongjinglong individual discovered was a medium-sized Titanosaur. Anatomical evidence, however, points to it being a juvenile; adults may have been larger.
The find, reported in the journal PLOS ONE, helps clarify relationships among several sauropod species that have been found in the last few decades in China and elsewhere. Its features suggest that Yongjinglong is among the most derived, or evolutionarily advanced, of the Titanosaurs yet discovered from Asia.
Doctoral student Liguo Li and professor Peter Dodson, who have affiliations in both the School of Veterinary Medicine’s Department of Animal Biology and the School of Arts and Sciences’ Department of Earth and Environmental Science, led the work. They partnered with Hailu You, a former student of Dodson’s, who now works at the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology, and Daqing Li of the Gansu Geological Museum in Lanzhou, China.
Until very recently, the United States was the epicenter for dinosaur diversity, but China surpassed the U.S. in 2007 in terms of species found. This latest discovery was made in the southeastern Lanzhou-Minhe Basin of China’s Gansu Province, about an hour’s drive from the province’s capital, Lanzhou. Two other Titanosaurs from the same period, Huanghetitan liujiaxiaensis and Daxiatitan binglingi, were discovered within the last decade in a valley one kilometer from the Yongjinglong fossils.
“As recently as 1997 only a handful of dinosaurs were known from Gansu,” Dodson said. “Now it’s one of the leading areas of China. This dinosaur is one more of the treasures of Gansu.”
During a trip to Gansu, Liguo Li was invited to study the remains, which had been in storage since being unearthed in 2008. They consisted of three teeth, eight vertebrae, the left shoulder blade, and the right radius and ulna.
The anatomical features of the bones bear some resemblance to another Titanosaur that had been discovered by paleontologists in China in 1929, named Euhelopus zdanskyi. But the team was able to identify a number of unique characteristics.
“The shoulder blade was very long, nearly 2 meters, with sides that were nearly parallel, unlike many other Titanosaurs whose scapulae bow outward,” Li said.
The scapula was so long, indeed, that it did not appear to fit in the animal’s body cavity if placed in a horizontal or vertical orientation, as is the case with other dinosaurs. Instead, Li and colleagues suggest the bone must have been oriented at an angle of 50 degrees from the horizontal.
In addition, an unfused portion of the shoulder blade indicated to the researchers that the animal under investigation was a juvenile or subadult.
“The scapula and coracoid aren’t fused here,” Li said. “It is open, leaving potential for growth.”
Thus, a full-grown adult might be larger than this 50-60 foot long individual. Future finds may help elucidate just how much larger, the researchers noted.
The ulna and radius were well preserved, enough so that the researchers could identify grooves and ridges they believe correspond with the locations of muscle attachments in the dinosaur’s leg.
The researchers were also able to draw evidence about the dinosaur’s relationship to other species from the vertebrae, one of which was from the neck and the other seven from the trunk. Notably, the vertebrae had large cavities in the interior that the team believes provided space for air sacs in the dinosaur’s body.
“These spaces are unusually large in this species,” Dodson said. “It’s believed that dinosaurs, like birds, had air sacs in their trunk, abdominal cavity and neck as a way of lightening the body.”
In addition, the longest tooth they found was nearly 15 centimeters long. Another shorter tooth contained unique characteristics, including two “buttresses,” or bony ridges, on the internal side, while Euhelopus had only one buttress on its teeth.
To gain a sense of where Yongjinglong sits on the family tree of sauropods, the researchers were able to compare its characteristics with specimens from elsewhere in China, as well as from Africa, South America and the U.S.
“We used standard paleontological techniques to compare it with phylogenies based on other specimens,” Dodson said. “It is definitely much more derived than Euhelopus and shows close similarities to derived species from South America.”
Not only does the discovery point to the fact that Titanosaurs encompass a diverse group of dinosaurs, but it also supports the growing consensus that sauropods were a dominant group in the Early Cretaceous — a view that U.S. specimens alone could not confirm.
“Based on U.S. fossils, it was once thought that sauropods dominated herbivorous dinosaur fauna during the Jurassic but became almost extinct during the Cretaceous,” Dodson said. “We now realize that, in other parts of the world, particularly in South America and Asia, sauropod dinosaurs continued to flourish in the Cretaceous, so the thought that they were minor components is no longer a tenable view.”
Note : The above story is based on materials provided by University of Pennsylvania. Note: Materials may be edited for content and length.
Ancient rocks in Quebec hold secrets to the early Earth
Provocative new research published this month in the journal Geology suggests that oceanic plate subduction was operating from the earliest times in Earth’s history, meaning conditions for the formation of life may have existed up to a billion years earlier than generally thought.
These findings came from a team of Australian researchers, who analysed similarities between modern-day subduction zones near Japan and early-Earth rock sequences from Quebec, Canada.
Subduction is a process whereby an oceanic plate descends beneath another plate (a characteristic of modern plate tectonics).
Lead author, Macquarie University’s Professor Simon Turner says, “Modern subduction settings, such as the Mariana arc, have all the right chemical ingredients to grow and sustain primitive life forms.
“From the similarities of our research into the earlier deposits from Canada, it follows that the conditions for the formation of life may have existed much earlier, with subduction starting far longer ago than we’d thought previously.”
The early Earth’s geological processes remain a fundamental question for the earth sciences and the rareness of rocks from this time period make exploration a significant challenge.
“We expect that this research will result in a lot of debate across the discipline, as there’s much that is yet to be discovered in the processes and earliest records of subduction. Our next steps are to investigate Zn isotopes which could show whether high pH fluids were present to stabilise amino acids, and we’ll continue to explore the secrets under the Earth’s crust”.
Note : The above story is based on materials provided by Macquarie University
Degassing lava erupts onto the seafloor at NW Rota-1 volcano, creating a billowing cloudy plume that is extremely acidic, and is full of carbon dioxide and sulfur. Credit: Woods Hole Oceanographic Institution
Oregon State University scientists have discovered how to pinpoint the time and place of underwater volcanic eruptions using satellite images.
Volcanic eruptions on the ocean floor can spew large amounts of pumice and fine particles, as well as hot water that brings nutrients to the surface, resulting in plumes of algae. The plumes are picked up as shades of green in satellite images.
“Some volcanic eruptions take place hundreds of feet below water and show no changes to the sea surface to the naked eye,” said Robert O’Malley, an OSU research assistant in botany and plant pathology in OSU’s College of Agricultural Sciences. “It’s amazing an orbiting satellite can detect color changes that indicate an eruption has taken place. Many times you can’t spot an eruption if you were floating over it in a boat.”
Underwater volcanic eruptions are rarely detected, so little is known about them, according to Mike Behrenfeld, an OSU expert in marine algae and and one of the researchers on the project.
“Satellite measurements of the planet are made every day,” Behrenfeld said, “so this new method provides another tool for spotting these dramatic events that affect life in the oceans.”
O’Malley and Behrenfeld developed a process for analyzing low-resolution images to show evidence of eruptions, which can extend over thousands of square miles, by matching five known eruptions with data from NASA satellites.
“We measured sunlight going into the ocean interacting with particles consistent with underwater volcanic eruptions,” said O’Malley. “From there, we found we could connect color data with documented eruptions. Now we have a better idea of what to look for in the data when we don’t know about the eruption first.”
Next, the researchers plan to test how well their method works as eruptions are happening. Further study will also focus on the depth at which eruptions can be detected.
The study was published in the journal Remote Sensing of the Environment.
Note : The above story is based on materials provided by Oregon State University
Chemical Formula: Na3[AlF6] Locality: Ivigtut and Arksukfiord, West Greenland. Name Origin: Named from the Greek, kryos “frost” and lithos “stone.”
Cryolite (Na3[AlF6]), sodium hexafluoroaluminate) is an uncommon mineral identified with the once large deposit at Ivigtût on the west coast of Greenland, depleted by 1987.
It was historically used as an ore of aluminium and later in the electrolytic processing of the aluminium-rich oxide ore bauxite (itself a combination of aluminium oxide minerals such as gibbsite, boehmite and diaspore). The difficulty of separating aluminium from oxygen in the oxide ores was overcome by the use of cryolite as a flux to dissolve the oxide mineral(s).
Pure cryolite itself melts at 1012 °C (1285 K), and it can dissolve the aluminium oxides sufficiently well to allow easy extraction of the aluminium by electrolysis. Substantial energy is still needed for both heating the materials and the electrolysis, but it is much more energy-efficient than melting the oxides themselves. As natural cryolite is too rare to be used for this purpose, synthetic sodium aluminium fluoride is produced from the common mineral fluorite.
Cryolite occurs as glassy, colorless, white-reddish to gray-black prismatic monoclinic crystals. It has a Mohs hardness of 2.5 to 3 and a specific gravity of about 2.95 to 3.0. It is translucent to transparent with a very low refractive index of about 1.34, which is very close to that of water; thus if immersed in water, cryolite becomes essentially invisible.
Cryolite has also been reported at Pikes Peak, Colorado; Mont Saint-Hilaire, Quebec; and at Miass, Russia. It is also known in small quantities in Brazil, the Czech Republic, Namibia, Norway, Ukraine, and several American states.
Cryolite was first described in 1799 from a deposit of it in Ivigtut and nearby Arsuk Fjord, Southwest Greenland. The name is derived from the Greek language words cryò = chill, and lithòs = stone. The Pennsylvania Salt Manufacturing Company used large amounts of cryolite to make caustic soda at its Natrona, Pennsylvania works during the 19th and 20th centuries.
Physical Properties of Cryolite
Cleavage: None Color: Brownish black, Colorless, Gray, White, Reddish brown. Density: 2.95 – 3, Average = 2.97 Diaphaneity: Transparent to translucent Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern. Hardness: 2.5-3 – Finger Nail-Calcite Luminescence: Fluorescent, Short UV=bluish white. Luster: Vitreous – Greasy Streak: white
A new study led by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science uncovered a previously unknown magma chamber deep below the most active volcano in the world – Kilauea.Credit: Image courtesy of University of Miami Rosenstiel School of Marine & Atmospheric Science
A new study led by scientists at the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science uncovered a previously unknown magma chamber deep below the most active volcano in the world — Kilauea. This is the first geophysical observation that large magma chambers exist in the deeper parts of the volcano system.
Scientists analyzed the seismic waves that travel through the volcano to understand the internal structure of the volcanic system. Using the seismic data, the researchers developed a three-dimensional velocity model of a magma anomaly to determine the size, depth and composition of the lava chamber, which is several kilometers in diameter and located at a depth of 8-11 km (5 — 6.8 miles).
“It was known before that Kilauea had small, shallow magma chambers,” said Guoqing Lin, UM Rosenstiel School assistant professor of geology and geophysics and lead author of the study. “This study is the first geophysical observation that large magma chambers exist in the deep oceanic crust below.”
The study also showed that the deep chamber is composed of “magma mush,” a mixture of 10-percent magma and 90-percent rock. The crustal magma reservoir below Kilauea is similar to those widely observed beneath volcanoes located at mid-ocean ridges.
“Understanding these magma bodies are a high priority because of the hazard posed by the volcano,” said Falk Amelung, co-author and professor of geology and geophysics at the UM Rosenstiel School. “Kilauea volcano produces many small earthquakes and paying particular attention to new seismic activity near this body will help us to better understand where future lava eruptions will come from.”
Scientists are still unraveling the mysteries of the deep internal network of magma chambers and lava tubes of Kilauea, which has been in continuous eruption for more than 30 years and is currently the most active volcano in the world.
Note : The above story is based on materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science. Note: Materials may be edited for content and length.
The Neoproterozoic Era is the unit of geologic time from 1,000 to 541 million years ago.
The terminal Era of the formal Proterozoic Eon (or the informal “Precambrian”), it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods.
The most severe glaciation known in the geologic record occurred during the Cryogenian, when ice sheets reached the equator and formed a possible “Snowball Earth”.
The earliest fossils of multicellular life are found in the Ediacaran, including the earliest animals.
Geology
At the onset of the Neoproterozoic the supercontinent Rodinia, which had assembled during the late Mesoproterozoic, straddled the equator. During the Tonian, rifting commenced which broke Rodinia into a number of individual land masses.
Possibly as a consequence of the low-latitude position of most continents, several large-scale glacial events occurred during the Neoproterozoic Era including the Sturtian and Marinoan glaciations of the Cryogenian.
These glaciations are believed to have been so severe that there were ice sheets at the equator—a state known as the “Snowball Earth”.
Subdivisions
The Russians divide the Siberian Neoproterozoic into the Baikalian from 850 to 650 Ma (loosely equivalent to the Cryogenian), which overlies the Mayanian, from 1000 to 850 Ma, then the Aimchanian.
Paleobiology
The idea of the Neoproterozoic Era came on the scene relatively recently — after about 1960. Nineteenth century paleontologists set the start of multicelled life at the first appearance of hard-shelled animals called trilobites and archeocyathids.
This set the beginning of the Cambrian period. In the early 20th century, paleontologists started finding fossils of multicellular animals that predated the Cambrian boundary. A complex fauna was found in South West Africa in the 1920s but was misdated.
Another was found in South Australia in the 1940s but was not thoroughly examined until the late 1950s. Other possible early fossils were found in Russia, England, Canada, and elsewhere (see Ediacaran biota). Some were determined to be pseudofossils, but others were revealed to be members of rather complex biotas that are still poorly understood. At least 25 regions worldwide yielded metazoan fossils prior to the classical Cambrian boundary.
A few of the early animals appear possibly to be ancestors of modern animals. Most fall into ambiguous groups of frond-like organisms; discoids that might be holdfasts for stalked organisms (“medusoids”); mattress-like forms; small calcaerous tubes; and armored animals of unknown provenance.
These were most commonly known as Vendian biota until the formal naming of the Period, and are currently known as Ediacaran biota. Most were soft bodied. The relationships, if any, to modern forms are obscure. Some paleontologists relate many or most of these forms to modern animals. Others acknowledge a few possible or even likely relationships but feel that most of the Ediacaran forms are representatives of unknown animal types.
In addition to Ediacaran biota, later two other types of biota were discovered in China (the so-called Doushantuo formation and Hainan formation).
Terminal period
The nomenclature for the terminal period of the Neoproterozoic has been unstable. Russian geologists referred to the last period of the Neoproterozoic as the Vendian, while Chinese geologists referred to it as the Sinian, and most Australians and North Americans used the name Ediacaran.
However, in 2004, the International Union of Geological Sciences ratified the Ediacaran age to be a geological age of the Neoproterozoic, ranging from ~635 to 541.0 ± 1.0 million years ago. The Ediacaran boundaries are the only Precambrian boundaries defined by biologic Global Boundary Stratotype Section and Points, rather than the absolute Global Standard Stratigraphic Ages.
Note : The above story is based on materials provided by Wikipedia
The Mesoproterozoic Era is a geologic era that occurred from 1,600 to 1,000 million years ago. The Mesoproterozoic was the first period of Earth’s history of which a respectable geological record survives. Continents existed in the Paleoproterozoic, but we know little about them. The continental masses of the Mesoproterozoic are more or less the same ones that are with us today.
The major events of this era are the formation of the Rodinia supercontinent, the breakup of the Columbia supercontinent, and the evolution of sexual reproduction.
This era is marked by the further development of continental plates and plate tectonics. At the end of this era, the continental plates that had developed were more or less the same we have today. This is the first era of which a good geological record still exists today.
The first large-scale mountain building episode, the Grenville Orogeny, for which extensive evidence still survives, happened in this period.
This era was the high point of the Stromatolites before they declined in the Neoproterozoic.
The era saw the development of sexual reproduction, which greatly increased the complexity of life to come. It was the start of development of communal living among organisms, the multicellular organisms.
It was an Era of apparently critical, but still poorly understood, changes in the chemistry of the sea, the sediments of the earth, and the composition of the air. Oxygen levels had risen to perhaps 1% of today’s levels at the beginning of the era and continued rising throughout the Era.
Subdivisions
The subdivisions of the Mesoproterozoic are, obviously, arbitrary divisions based on time. They are not geostratigraphic or biostratigraphic units. The base of the Mesoproterozoic is defined chronometrically, in terms of years, rather than by the appearance or disappearance of some organism. This gives an illusory sense of certainty. Radiometric dating is a good tool, and gets better each decade.[citation needed] This creates some problems. As a practical matter, radiometric dates have an error margin of 1-2%. That sounds good, but it means that two sites, both measured to be at the exact base of the Ectasian, might differ in age by over 50 My. Since the Ectasian is only 200 My long, that’s a serious matter. And this accounts only for random error. Systematic errors can be caused by extraterrestrial events, by geochemical or biochemical sorting of isotopes, and human error. Thus far, biostratigraphy has usually proved considerably more exact. In addition, a thoughtful choice of biological marker can be used as a signal to expect a whole host of ecological changes. The difference between a Changhsingian and an Induan deposit isn’t just a matter of a few years. The world changed hugely at the end of the Permian.
By contrast, the transition from Calymmian to Ectasian has no meaning beyond calendar time. The usual reason given for the use of a chronometric system is that there is insufficient biological activity or geochemical change to find useful markers. That is a position which is now a little uncertain and is going to become increasingly tenuous over the next few years. For example, there are a number of good potential markers in the rise and decline of “Christmas tree” stromatolites, in the coming and going of banded iron formations, the appearance of stable carbon-13 isotope (13C) excursions, and so on. These have real meaning for the geologist and paleontologist.
For that matter, they are not completely without biological markers. There has been considerable progress in studying and identifying fossil bacteria and Eukarya. The cyanobacterium Archaeoellipsoides is one relatively common form, apparently known from several species. It is probably related to the extant Anabaena and indicates the presence of significant free oxygen. Oxygen levels also had significant effects on ocean chemistry; continental weathering rates increased and provided sulfates and nitrates as nutrients. It would be remarkable if this didn’t result in new populations of both bacterial and eukaryotic organisms. Since the presence of these cells would be tied directly to important geochemical events, they would make ideal organisms for biostratigraphy.
Note : The above story is based on materials provided by Wikipedia
The Paleoproterozoic is the first of the three sub-divisions (eras) of the Proterozoic occurring between 2,500 to 1,600 million years ago. This is when the continents first stabilized. This is also when cyanobacteria evolved, a type of bacteria which uses the biochemical process of photosynthesis to produce energy and oxygen.
Paleontological evidence on the Earth’s rotational history suggests that ~1.8 billion years ago, there were about 450 days in a year, implying 20 hour days.
Geography
Modern Plate tectonics began with the Paleoproterozoic. The Paleoproterozoic was the era of continental shield formation. By and large, the Earth’s Archean crust seems to have been both fragmented and somewhat unstable. Some paleogeographers assert that an episode of continent formation — in fact a supercontinent — was present at the end of the Archean. Kump & Barley (2007). However, if that was the case, then those continents were unstable and disappeared without a trace over the next few hundred My. The majority view is that modern style continents and familiar plate tectonics began not long before the Paleoproterozoic.
Continental shields formed from small cratons. It was during the Paleoproterozoic that small islands of crust were first stitched together to form the stable nuclei of the continents we know today. This may something of an overstatement, since relatively broad islands of Archean stability are found in the rocks northeastern Canada and Greenland (the Laurentian or Canadian Shield), Western Australia (Pilbarra Craton), and South Africa (Kapvaal Craton). These became the nuclei of the North American, Australian, and (in part) African continents, respectively. However, even in these cases, the continental craton in its present form was the product of suturing several smaller units. That suturing process largely occurred in the Paleoproterozoic. In other cases (e.g., India, South America, and North China), both crust and shield were largely products of the Paleoproterozoic.
Now that we have extruded this patently over-broad generalization, we had best defend the thesis with some concrete examples.
For example, the core of South America formed around Amazonia in the Paleoproterozoic. The geologically stable core of South America is the Amazonian craton, roughly coterminous with northern and central Brazil and the inland areas of Venezuela, both Guyanas, and Suriname. Most of western South America is composed of ephemeral orogenic mountain ranges which come and go on timescales of a few 100 My. Other bits and pieces have joined (Uruguay) or left (Central Texas?) Amazonia at various times in the geological past. However, the unchanging hub of all this activity was Amazonia. The only other significant cratons now associated with South America, the São Francisco and Rio de la Plata, are both immigrants from Africa. Iacumin et al. (2001).
The only large stretches of Archean basement remaining in Amazonia are located in the eastern section of Amazonia, mostly in the southeastern corner. Most of the rest of Amazonia was intruded and sutured together in the Paleoproterozoic. The only significant exception is the northwestern Rio Negro Province, which lies along the Brazilian-Columbian border. This province formed as an extension of Amazonia in the Mesoproterozoic. Tassinari & Macambira (1999); Sial et al. (1999). For the subsequent development of the region, Brito Neves et al. (1999).
Baltica, the core of Europe, formed from the merger of three cratons in the Paleoproterozoic. The formation of Baltica – the continent which was to become Europe — is one of the best-known examples. Baltica formed in the Paleoproterozoic from the fusion of three cratons: Fennoscandia (Scandinavia, the Baltics, Belarus, Eastern Poland, part of Scotland, and northern European Russia), Volgo-Uralia (the Volga Basin of Russia), and Sarmatia (the Trans-Caucasus region, the Ukraine, Moldavia and part of Romania). Gee & Stephenson (2006). The process of consolidation was complete by the end of the Paleoproterozoic. Virtually all further growth in the Proterozoic came by way of extensional tectonics and the incorporation of bits and pieces of other adjacent continents. Bingen et al. (2008).
India has a similar history. Similarly, India appears to be an amalgamation of four cratons. One of these is a small, late accretion to the southern tip (southern Tamil Nadu and Kerala). The rest consists of three Archean cratons which consolidated at the end of the Paleoproterozoic. Sankaran (1999).
The shift in continent-building style is correlated with a shift in large volcanic belts from marine to terrestrial settings. Recently Kump & Barley (2007), devised an ingenious test of the general concept. They collected a large database of reasonably characterized “large igneous provinces.” LIPs are broad areas of volcanic activity. They are usually manifestations of the chafing and irritation which occurs when two cratons come in contact. During the Archean, the vast majority (80% or more) of LIPs happened under water. At the beginning of the Proterozoic, the proportions abruptly reverse. About 80% of known Proterozoic LIPs were terrestrial. The most parsimonious explanation is that cratons were now consolidating, so that the boundaries between adjacent cratons most often lay in the interior of larger masses — continents.
The trigger may have been the accumulation of a critical amount of rigid continental crust. In fact, something more fundamental may have happened — a change in the tectonic behavior of cratons somewhat analogous to a change of state between two crystal forms. The break between Archean and Proterozoic LIP locations is quite sharp, and the ~80% level is fairly steady for the rest of Earth history. The Early Paleoproterozoic is also the earliest time that normal plate boundaries, boundaries between essentially rigid crust elements, are seen in the geological record. Stanley (1998). Stanley also notes that the total volume of continental crust first approached present value at the end of the Archean. It seems likely that the volume of continental crust, the formation of continental shields, and the development of “normal” plate tectonics are related, although the mechanics have not been worked out.
Paleoatmosphere
Before the significant increase in atmospheric oxygen almost all life that existed was anaerobic, that is, the metabolism of life depended on a form of cellular respiration that did not require oxygen.
Free oxygen in large amounts is toxic to most anaerobic bacteria. It is widely believed that the majority of existent anaerobic life on Earth died off. The only life that remained was either resistant to the oxidizing and poisonous effects of oxygen, or spent its life-cycle in an oxygen-free environment. This main event is called the oxygen catastrophe.
Lifeforms
The crown eukaryotes, from which all modern day eukaryotic lineages have arisen have been dated to the paleoproterozoic era. By ~1 Gy the latest common ancestors between the ciliate and flagellate lineages probably diverged. The Francevillian Group and Grypania fossils and the first eukaryotes also appeared during this time.
Geological events
During this era the earliest global-scale continent-continent collisional belts developed.
These continent and mountain building events are represented by the 2.1-2.0 Ga (Ga = billion year) Transamazonian and Eburnean Orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma Orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China.
These continental collisional belts are interpreted as having resulted from 2.0-1.8 Ga global-scale collisional events that led to the assembly of a Paleo-Mesoproterozoic supercontinent named “Columbia” or “Nuna”.
Note : The above story is based on materials provided by Wikipedia , Palaeos
Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia.
The New Madrid fault zone in the United States’ midsection is active and could spawn future large earthquakes, scientists reported Thursday.
It’s “not dead yet,” said U.S. Geological Survey seismologist Susan Hough, who was part of the study published online by the journal Science.
Researchers have long debated just how much of a hazard New Madrid poses. The zone stretches 150 miles (250 kilometers), crossing parts of Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and Tennessee.
In 1811 and 1812, it unleashed a trio of powerful jolts—measuring magnitudes 7.5 to 7.7—that rattled the central Mississippi River valley. Chimneys fell and boats capsized. Farmland sank and turned into swamps. The death toll is unknown, but experts don’t believe there were mass casualties because the region was sparsely populated then.
Unlike California’s San Andreas and other faults that occur along boundaries of shifting tectonic plates, New Madrid is less understood since it’s in the middle of the continent, far from plate boundaries.
Previous studies have suggested that it may be shutting down, based on GPS readings that showed little strain accumulation at the surface. Other research came to the same conclusion by blaming ongoing quake activity on aftershocks from the 1800s, which would essentially relieve strain on the fault.
The latest study suggests otherwise. Hough and USGS geophysicist Morgan Page in Pasadena, California, analyzed past quakes in the New Madrid region and used computer modeling to determine that the continuing tremors are not related to the big quakes two centuries ago.
“Our new results tell us that something is going on there, and therefore a repeat of the 1811-1812 sequence is possible,” Hough said.
The USGS estimates there’s a 7 to 10 percent chance of that happening in the next 50 years.
Arthur Frankel, a seismologist with the USGS in Seattle who had no role in the study, said the latest results seem plausible. His recent field work using GPS shows significant movement of land along the fault in the past decade, indicating a buildup of strain that could lead to potentially dangerous quakes.
Others said this won’t end the debate about the hazards on the New Madrid seismic zone.
Andrew Newman, a geophysicist at the Georgia Institute of Technology, said the method used in the study works well for faults along plate boundaries, but he’s unsure if it applies to enigmatic faults like New Madrid.
Marine researchers from Bremen, along with a U.S. colleague, discovered the potential reasons for an unsolved mystery from beneath the seafloor – the study appeared online yesterday in Nature Geoscience. Their findings provide an explanation as to why methane in zones of turnover in the seafloor displays unusual isotopic signatures that have long puzzled researchers. The authors attribute the enigma to the process of methane oxidation by microorganisms, and suggest that this phenomenon may apply to other low-energy biogeochemical reactions that prevail in the marine realm.
Analyzing the carbon isotopic composition of methane within the seafloor, researchers from the MARUM and the Max-Planck-Institute for Marine Microbiology in Bremen came across an unusual phenomenon: In the zone where microorganisms oxidize methane along with reducing sulfate, there is no accumulation of the heavy isotope, 13C, in the remaining methane, as expected from traditional isotope behavior. Instead, they repeatedly find isotopically “light” methane – enriched in 12C – from a variety of such zones around the world. “These “light” methane signatures were previously interpreted as a fingerprint for methane production”, says Marcos Yoshinaga, first-author and currently a guest investigator at the School of Arts, Sciences and Humanities, University of São Paulo. “In this zone of methane oxidation, however, we could not think of any other biogeochemical process supporting this production”, adds senior-author Marcus Elvert from MARUM.
As a general rule, it has been proposed that during the process of methane oxidation there is a preferential loss of the lighter isotope from the starting reactant, with the remaining pool becoming isotopically “heavy” or enriched in 13C. The researchers used laboratory experiments to simulate microbial methane oxidation under similar conditions encountered in the seafloor. “The microbial collection of our Max-Planck-Institute with cultures of methane oxidizers from all over the world offers the possibility to faithfully reproduce the conditions found in nature” says Thomas Holler. And effectively: under low sulfate concentrations, as generally observed at methane oxidation zones in the seafloor, the formation of light, 12C-enriched methane occurred.
Methane possesses two major facets. Consisting of carbon and hydrogen atoms, it not only serves as energy source for microorganisms, but also plays a major role as a greenhouse gas. Marine sediments contain about 500–10,000 Gt of methane carbon. This reservoir is comparable in size to the amount of carbon in land biota, terrestrial soils, atmosphere and seawater combined, but thanks to the microbial methane oxidation in sediments devoid of oxygen, the oceans are responsible for less than two percent of the atmospheric emissions. “We have analyzed the stable carbon isotopic composition of methane in worldwide marine sediments” says John Pohlman from the US Geological Survey. Stable isotopes such as those of carbon contain the same number of protons but are distinct in the number of neutrons and thus have different masses. They show no difference in the chemical behavior during reactions, however, in chemical reactions, a preferential turnover of the lighter isotope 12C is observed during biogeochemical processes.
In addition to the environmental data, the researchers tried to answer the question why methane enriched in the lighter isotope 12C forms at low sulfate contents. Operating close to the energetic limit of life, all components of the methane oxidation reaction are close to isotope equilibrium. “As a consequence, the lighter isotope 12C is channeled back to methane”, says Gunter Wegener from the Max-Planck-Institute. “This result could be constrained by our biogeochemical model”, adds Tobias Goldhammer from MARUM. The researchers concluded that such low-energy reactions may also occur in the cycling of other elements within the Ocean’s interior. “This study highlights a novel insight into how certain Archaea adjust their metabolism to live under strong energy limitation in the deep-biosphere, and at the same time answers a central question of our project”, says Kai-Uwe Hinrichs, co-author and leader of the European Research Council-funded Project DARCLIFE that supported this study.
Note :The above story is based on materials provided by MARUM
Chemical Formula: Pb2CuCl2(OH)4 Locality: Higher Pitts, Mendip Hills, Somersetshire, England. Name Origin: From the Greek dia, “difference” and the mineral Boleite.
Diaboleite is a blue-colored mineral with formula Pb2CuCl2(OH)4. It was discovered in England in 1923 and named diaboleite, from the Greek word διά and boleite, meaning “distinct from boleite”. The mineral has since been found in a number of countries.
Description
Diaboleite is deep blue in color and pale blue in transmitted light. The mineral occurs as tabular crystals up to 2 cm (0.8 in) in size, as subparallel aggregates, or it has massive habit. Vicinal forms of the tabular crystals have a square or octagonal outline and rarely exhibit pyramidal hemihedralism.
Physical Properties of Diaboleite
Cleavage: {001} Perfect Color: Dark blue, Bright sky blue. Density: 5.48 – 6.41, Average = 5.94 Diaphaneity: Transparent to Translucent Fracture: Conchoidal – Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). Hardness: 2.5 – Finger Nail Luster: Adamantine Streak: blue
This screenshot from a supercomputer simulation shows the waveguide-to-basin effect in Southern California. First predicted in 2006, this effect has remained untested because a large earthquake has not occurred in the region in more than 150 years. Stanford scientists recently confirmed the effect using the virtual earthquake approach. (Credit: Courtesy of Southern California Earthquake Center)
Stanford scientists are using weak vibrations generated by Earth’s oceans to produce “virtual earthquakes” that can be used to predict the ground movement and shaking hazard to buildings from real quakes.
The new technique, detailed in the Jan. 24 issue of the journal Science, was used to confirm a prediction that Los Angeles will experience stronger-than-expected ground movement if a major quake occurs south of the city.
“We used our virtual earthquake approach to reconstruct large earthquakes on the southern San Andreas Fault and studied the responses of the urban environment of Los Angeles to such earthquakes,” said lead author Marine Denolle, who recently received her PhD in geophysics from Stanford and is now at the Scripps Institution of Oceanography in San Diego.
The new technique capitalizes on the fact that earthquakes aren’t the only sources of seismic waves. “If you put a seismometer in the ground and there’s no earthquake, what do you record? It turns out that you record something,” said study leader Greg Beroza, a geophysics professor at Stanford.
What the instruments will pick up is a weak, continuous signal known as the ambient seismic field. This omnipresent field is generated by ocean waves interacting with the solid Earth. When the waves collide with each other, they generate a pressure pulse that travels through the ocean to the sea floor and into Earth’s crust. “These waves are billions of times weaker than the seismic waves generated by earthquakes,” Beroza said.
Scientists have known about the ambient seismic field for about 100 years, but it was largely considered a nuisance because it interferes with their ability to study earthquakes. The tenuous seismic waves that make up this field propagate every which way through the crust. But in the past decade, seismologists developed signal-processing techniques that allow them to isolate certain waves; in particular, those traveling through one seismometer and then another one downstream.
Denolle built upon these techniques and devised a way to make these ambient seismic waves function as proxies for seismic waves generated by real earthquakes. By studying how the ambient waves moved underground, the researchers were able to predict the actions of much stronger waves from powerful earthquakes.
She began by installing several seismometers along the San Andreas Fault to specifically measure ambient seismic waves.
Employing data from the seismometers, the group then used mathematical techniques they developed to make the waves appear as if they originated deep within Earth. This was done to correct for the fact that the seismometers Denolle installed were located at Earth’s surface, whereas real earthquakes occur at depth.
In the study, the team used their virtual earthquake approach to confirm the accuracy of a prediction, made in 2006 by supercomputer simulations, that if the southern San Andreas Fault section of California were to rupture and spawn an earthquake, some of the seismic waves traveling northward would be funneled toward Los Angeles along a 60-mile-long (100-kilometer-long) natural conduit that connects the city with the San Bernardino Valley. This passageway is composed mostly of sediments, and acts to amplify and direct waves toward the Los Angeles region.
Until now, there was no way to test whether this funneling action, known as the waveguide-to-basin effect, actually takes place because a major quake has not occurred along that particular section of the San Andreas Fault in more than 150 years.
The virtual earthquake approach also predicts that seismic waves will become further amplified when they reach Los Angeles because the city sits atop a large sedimentary basin. To understand why this occurs, study coauthor Eric Dunham, an assistant professor of geophysics at Stanford, said to imagine taking a block of plastic foam, cutting out a bowl-shaped hole in the middle, and filling the cavity with gelatin. In this analogy, the plastic foam is a stand-in for rocks, while the gelatin is like sediments, or dirt. “The gelatin is floppier and a lot more compliant. If you shake the whole thing, you’re going to get some motion in the Styrofoam, but most of what you’re going to see is the basin oscillating,” Dunham said.
As a result, the scientists say, Los Angeles could be at risk for stronger, and more variable, ground motion if a large earthquake — magnitude 7.0 or greater — were to occur along the southern San Andreas Fault, near the Salton Sea.
“The seismic waves are essentially guided into the sedimentary basin that underlies Los Angeles,” Beroza said. “Once there, the waves reverberate and are amplified, causing stronger shaking than would otherwise occur.”
Beroza’s group is planning to test the virtual earthquake approach in other cities around the world that are built atop sedimentary basins, such as Tokyo, Mexico City, Seattle and parts of the San Francisco Bay area. “All of these cities are earthquake threatened, and all of them have an extra threat because of the basin amplification effect,” Beroza said.
Because the technique is relatively inexpensive, it could also be useful for forecasting ground motion in developing countries. “You don’t need large supercomputers to run the simulations,” Denolle said.
In addition to studying earthquakes that have yet to occur, the technique could also be used as a kind of “seismological time machine” to recreate the seismic signatures of temblors that shook Earth long ago, according to Beroza.
“For an earthquake that occurred 200 years ago, if you know where the fault was, you could deploy instruments, go through this procedure, and generate seismograms for earthquakes that occurred before seismographs were invented,” he said.
German Prieto, an assistant professor of geophysics at the Massachusetts Institute of Technology and a Stanford alumnus, also contributed to the research.
Video :
Note :The above story is based on materials provided by Stanford University. The original article was written by Ker Than.
Polarstern. In spring 2010, the research icebreaker Polarstern returned from the South Pacific with a scientific treasure — ocean sediments from a previously almost unexplored part of the South Polar Sea. (Credit: Martin Schiller, Alfred Wegener Institute)
In spring 2010, the research icebreaker Polarstern returned from the South Pacific with a scientific treasure — ocean sediments from a previously almost unexplored part of the South Polar Sea. What looks like an inconspicuous sample of mud to a layman is, to geological history researchers, a valuable archive from which they can reconstruct the climatic history of the polar areas over many years of analysis. This, in turn, is of fundamental importance for understanding global climatic development.
With the help of the unique sediment cores from the Southern Ocean, it is now possible to provide complete evidence of how dust has had a major influence on the natural exchange between cold and warm periods in the southern hemisphere. An international research team under the management of the Alfred Wegener Institute in Bremerhaven was able to prove that dust infiltrations there were 2 to 3 times higher during all the ice ages in the last million years than in the warm phases in climatic history.
“High large-area dust supply can have an effect on the climate for two major reasons,” explained Dr. Frank Lamy, geoscientist at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, about the findings. “Trace substances such as iron, which are essential for life, can be incorporated into the ocean through dust. This stimulates biological production and increases the sea’s capacity to bind carbon. The result is that the greenhouse gas carbon dioxide is taken out of the atmosphere. In the atmosphere itself, dust reflects the sun’s radiation and purely due to this it reduces the heat input into Earth’s system. Both effects lead to the fact that the Earth cools down.” Lamy is the main author of the study which will be published in the journal Science on the 24th January 2014. Other participants included geochemist Gisela Winckler from the US Lamont-Doherty Earth Observatory and the Bremen Centre for Marine Environmental Sciences MARUM.
The influence of dust supply on the climate changes between ice ages and warm periods has long been suspected. Climatic researchers always found particularly high dust content containing iron when Earth was going through an ice age, both in Antarctic ice cores and in sediment cores from the Atlantic part of the Southern Ocean. However, up to now there was no data available for the Pacific section, which covers 50% of the Southern Ocean. “We can now close this central gap” is how Lamy underlines the importance of the new study. “The result is that we are now finding the same patterns in the South Pacific that we found in cores from the South Atlantic and the Antarctic ice. Therefore, the increased dust input was a phenomenon affecting the southern hemisphere during colder periods. This means that they now have to be considered differently when assessing the complex mechanisms which control natural climate changes.”
What sounds almost incidental in Lamy’s words is something of considerable relevance for research. This is because up to now many scientists were convinced that dust supply to the Pacific area could not have been higher during the ice ages than during warmer periods of Earth’s climate history. Where could larger dust quantities in this area of Earth’s oceans come from? Up to now, South Patagonia was suspected as a geological dust source since it is the only landmass in the Southern Ocean, intruding into it like a huge finger. However, since the wind predominating in this part of the world comes from the West, any dust particles in the air originating from South America mostly drift towards the Atlantic. For this reason, data from the South Pacific has been on scientists’ wishlists for a long time.
However, the Pacific section of the Southern Ocean has remained something of a “terra incognita” for researchers despite modern technology. It is considered to be one of the most remote parts of the world’s oceans. “The region is influenced by extreme storms and swells in which wave heights of 10 m or more are not uncommon. The area is also complicated from logistic point of view due to the huge distance between larger harbours” is how AWI scientist Dr. Rainer Gersonde, co-author and at the time leader of the Polarstern expedition, explains the extraordinary challenges faced by the research voyage. The Polarstern made a voyage of 10,000 nautical miles or 18,500 km through this particularly inhospitable part of the Antarctic Ocean in order to obtain high quality and sufficiently long sediment cores.
The question is, however, where did the historic dust freight towards the South Pacific come from, and why did the phases of increased input take place at all? Frank Lamy believes that one of the causes is the relocation or extension of the exceptionally strong wind belts prevalent in this region towards the Equator. The entire Southern Ocean is notorious amongst sailors for its powerful westerly winds — the “Roaring Forties” and the “Furious Fifties.” It is considered to be one of the windiest regions in the world. The scientists’ theory is that a relocation or extension of this powerful westerly wind belt towards the North could have caused the extended dry areas on the Australian continent to be influenced by stronger wind erosion. The result was higher dust infiltration into the Pacific Ocean — with the consequences described above. On top of this, New Zealand was an additional dust source. The extended glaciation of the mountains there during the ice age provided considerable quantities of fine-grained material which was then blown far out into the South Pacific by the winds.
“Our investigations have now proved without a doubt that colder periods in the southern hemisphere over a period of 1 million years always and almost everywhere coincided, , with lower carbon dioxide content in the atmosphere and higher dust supply from the air. The climatic history of the Earth was, therefore, written in dust.”
Note : The above story is based on materials provided by Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research, via EurekAlert!, a service of AAAS.
The surfaces of tiny interplanetary dust particles are space-weathered by the solar wind, causing amorphous rims to form on their surfaces. Hydrogen ions in the solar wind react with oxygen in the rims to form tiny water-filled vesicles (blue). This mechanism of water formation almost certainly occurs in other planetary systems with potential implications for the origin of life throughout the galaxy. (Credit: John Bradley, UH SOEST/ LLNL)
Researchers from the University of Hawaii — Manoa (UHM) School of Ocean and Earth Science and Technology (SOEST), Lawrence Livermore National Laboratory, Lawrence Berkeley National Laboratory, and University of California — Berkeley discovered that interplanetary dust particles (IDPs) could deliver water and organics to Earth and other terrestrial planets.
Interplanetary dust, dust that has come from comets, asteroids, and leftover debris from the birth of the solar system, continually rains down on Earth and other Solar System bodies. These particles are bombarded by solar wind, predominately hydrogen ions. This ion bombardment knocks the atoms out of order in the silicate mineral crystal and leaves behind oxygen that is more available to react with hydrogen, for example, to create water molecules.
“It is a thrilling possibility that this influx of dust has acted as a continuous rainfall of little reaction vessels containing both the water and organics needed for the eventual origin of life on Earth and possibly Mars,” said Hope Ishii, new Associate Researcher in the Hawaii Institute of Geophysics and Planetology (HIGP) at UHM SOEST and co-author of the study. This mechanism of delivering both water and organics simultaneously would also work for exoplanets, worlds that orbit other stars. These raw ingredients of dust and hydrogen ions from their parent star would allow the process to happen in almost any planetary system.
Implications of this work are potentially huge: Airless bodies in space such as asteroids and the Moon, with ubiquitous silicate minerals, are constantly being exposed to solar wind irradiation that can generate water. In fact, this mechanism of water formation would help explain remotely sensed data of the Moon, which discovered OH and preliminary water, and possibly explains the source of water ice in permanently shadowed regions of the Moon.
“Perhaps more exciting,” said Ishii, “interplanetary dust, especially dust from primitive asteroids and comets, has long been known to carry organic carbon species that survive entering the Earth’s atmosphere, and we have now demonstrated that it also carries solar-wind-generated water. So we have shown for the first time that water and organics can be delivered together.”
It has been known since the Apollo-era, when astronauts brought back rocks and soil from the Moon, that solar wind causes the chemical makeup of the dust’s surface layer to change. Hence, the idea that solar wind irradiation might produce water-species has been around since then, but whether it actually does produce water has been debated. The reasons for the uncertainty are that the amount of water produced is small and it is localized in very thin rims on the surfaces of silicate minerals so that older analytical techniques were unable to confirm the presence of water.
Using a state-of-the-art transmission electron microscope, the scientists have now actually detected water produced by solar-wind irradiation in the space-weathered rims on silicate minerals in interplanetary dust particles. Futher, on the bases of laboratory-irradiated minerals that have similar amorphous rims, they were able to conclude that the water forms from the interaction of solar wind hydrogen ions (H+) with oxygen in the silicate mineral grains.
This recent work does not suggest how much water may have been delivered to Earth in this manner from IDPs.
“In no way do we suggest that it was sufficient to form oceans, for example,” said Ishii. “However, the relevance of our work is not the origin of the Earth’s oceans but that we have shown continuous, co-delivery of water and organics intimately intermixed.”
In future work, the scientists will attempt to estimate water abundances delivered to Earth by IDPs. Further, they will explore in more detail what other organic (carbon-based) and inorganic species are present in the water in the vesicles in interplanetary dust rims.
Note : The above story is based on materials provided by University of Hawaii.
