During the earliest stages of the Earth’s formation, the planet’s mantle may have taken the form of a giant magma ocean, being fully or partially molten all the way down to the core-mantle boundary. Though today mantle material is predominantly solid, some scientists suggest that regions of anomalously low seismic wave velocity deep within the mantle, known as ultralow velocity zones (ULVZs), may be indicative of a remnant magma ocean or of partial melting of minerals near the core-mantle boundary. To understand how the early mantle solidified, or whether modern melt could be the source of ULVZs, scientists need to know how various minerals and melts behave under the extreme conditions found near the center of the Earth.
Through the use of various techniques, Thomas et al.analyzed how the density of molten fayalite—an iron-bearing silicate mineral—behaved under pressures up to 161 gigapascals, surpassing those at the core-mantle boundary.
The research adds to previous investigations into the equation of state of fayalite, an expression describing how the material’s density responds to changes in temperature and pressure. The authors find that iron-bearing fayalite behaves similarly to nonferrous silicate liquids during compression and heating.
Based on the measured equation of state, and on the known behavior of other silicate liquids, the authors suggest that the solidification of the Earth’s early mantle would have started near the core-mantle boundary or in the lower mantle.
Based on the current research, the authors are unable to determine whether ultralow velocity zones are necessarily caused by partial melting of the mantle material. They did, however, identify a potential set of liquid compositions that would be gravitationally stable if present.
Researchers established the age of the various rocks on Christmas Island at the time they were erupted, and established the position of the island through time. Credit: Peter McKiernan
Geological samples from Christmas Island have been analysed by a West Australian scientist, giving valuable insight into its unique volcanic history.
Curtin University geochronologist Dr Fred Jourdan says while continents are often the subject of geological investigation, ocean geology is less studied and the results of the Christmas Island study adds important information to the field.
The report he co-authored has been published in Gondwana Research.
It describes the Christmas Island area as an extensive zone of volcanism in the north-east Indian Ocean, consisting of numerous submerged seamounts and flat topped guyots.
It explains the island has experienced multiple episodes of volcanism that are exposed sporadically along its coastline.
It is the only island in the region to show intraplate volcanism in the form of basaltic rocks that are exposed above sea level.
Dr Jourdan says the project was a collaboration with Macquarie University. Samples were collected by a student from Macquarie University and tested at Curtin University using 40Ar/39Ar geochronology and paleomagnetism.
Dr Jourdan says this is where the ‘real science’ of finding their origin began.
“What we did was two things; we established the age of the various rocks on the island at the time they were erupted, and we established the position of the island through time,” he says.
“We needed to look at where it was before, to understand why there is volcanic activity at all—is it random or related to something in particular?
“We measured two different ages but we know, comparing it to other seamounts, there are in fact three periods of volcanic activity.
Three stages of Christmas Island volcanic activity
“The oldest happened when Australia and India separated and the rock left behind melted to create a seamount—that was the first volcanic activity, although we didn’t sample this and at this time, the island was much further south than it is now.
“The second, happened between 43 and 37 million years ago—it happened when the continent moved north above a hot zone in the mantle.
“Nothing happened for 30 million years until, in its northward movement toward the European-Asian plate; the plate cracked five million years ago and the magma could easily rise through the cracks.”
Dr Jourdan says similar low volume intraplate volcanism had previously been observed at similar tectonic settings to the Japan and Tonga trench.
“…We put forward the Indo Australian plate subduction setting as a likely candidate for this phase of introceanic volcanism.”
More information:
Rajat Taneja, Craig O’Neill, Mark Lackie, Tracy Rushmer, Phil Schmidt, Fred Jourdan, “40Ar/39Ar geochronology and the paleoposition of Christmas Island (Australia), Northeast Indian Ocean,” Gondwana Research, Available online 27 April 2014, ISSN 1342-937X, dx.doi.org/10.1016/j.gr.2014.04.004.
Note : The above story is based on materials provided by Science Network WA
Chemical Formula: FeAs2 Locality: Lölling, Hüttenberg, Carinthia, Austria Name Origin: Named after its locality.
Loellingite, also spelled löllingite, is an iron arsenide mineral with formula FeAs2. It is often found associated with arsenopyrite (FeAsS) from which it is hard to distinguish. Cobalt, nickel and sulfur substitute in the structure. The orthorhombic lollingite group includes the nickel iron arsenide rammelsbergite and the cobalt iron arsenide safflorite. Leucopyrite is an old synonym for loellingite.
It forms opaque silvery white orthorhombic prismatic crystals often exhibiting crystal twinning. It also occurs in anhedral masses and tarnishes on exposure to air. It has a Mohs hardness of 5.5 to 6 and a quite high specific gravity of 7.1 to 7.5. It becomes magnetic after heating.
Loellingite was first described in 1845 at the Lölling district in Carinthia, Austria, for which it was named.
It occurs in mesothermal ore deposits associated with skutterudite, native bismuth, nickeline, nickel-skutterudite, siderite and calcite. It has also been reported from pegmatites.
New research, published this week, has provided scientists with greater insight into the climatic changes happening in the upper atmosphere. Scientists found that changes in the Earth’s magnetic field are more relevant for climatic changes in the upper atmosphere (about 100-500 km above the surface) than previously thought. Understanding the cause of long-term change in this area helps scientists to predict what will happen in the future. This has key implications for life back on earth.
A good understanding of the long-term behaviour of the upper atmosphere is essential; it affects a lot of satellite-based technology, such as global navigation systems and high-frequency radio communication systems. Some satellites even operate within the upper atmosphere itself.
The increase in atmospheric CO2 concentration has been thought to be the main cause of climatic changes at these high altitudes. This study suggests that magnetic field changes that have taken place over the past century are as important.
Both increasing levels of CO2 and changes in the Earth’s magnetic field affect the upper atmosphere, including its charged portion, also known as the ionosphere. Dr. Ingrid Cnossen from the British Antarctic Survey used computer simulations to compare the effects of these two factors over the past century.
While CO2 causes heat to be trapped in the lower atmosphere, it actually cools the upper atmosphere. The simulations show that the increase in CO2 concentration over the past 100 years has caused the upper atmosphere, at around 300 km altitude, to cool by around 8 degrees. At the same altitude, changes in the Earth’s magnetic field caused a similar amount of cooling over parts of North America, but caused a warming over other parts of the world, with the strongest warming, of up to 12 degrees, located over Antarctica.
Dr. Ingrid Cnossen said: “Computer simulations are a very important tool in understanding the causes of climate change at high altitudes. We still can’t explain all of the long-term trends that have been observed, but it helps that we now know how important the magnetic field is.”
The new simulations also indicate that rising CO2 levels have caused the densest part of the ionosphere to lower by about 5 km globally. Changes in the Earth’s magnetic field can cause much larger changes, but they are very dependent on location and can be either positive or negative; over the southern Atlantic Ocean a decrease in height of up to 50 km was found, while an increase in height of up to 20 km was found over western Africa.
The findings are published in the Journal of Space Weather and Space Climate.
Note : The above story is based on materials provided by British Antarctic Survey
An Italian astronomer in the 19th century first described them as ‘canali’ – on Mars’ equatorial region, a conspicuous net-like system of deep gorges known as the Noctis Labyrinthus is clearly visible. The gorge system, in turn, leads into another massive canyon, the Valles Marineris, which is 4,000 km long, 200 km wide and 7 km deep. Both of these together would span the US completely from east to west.
As these gorges, when observed from orbit, resemble terrestrial canyons formed by water, most researchers assumed that immense flows of water must have carved the Noctis Labyrinthus and the Valles Marineris into the surface of Mars. Another possibility was that tectonic activity had created the largest rift valley on a planet in our solar system.
Lava flows caused the gorges
These assumptions were far from the mark, says Giovanni Leone, a specialist in planetary volcanism in the research group of ETH professor Paul Tackley. Only lava flows would have had the force and mass required to carve these gigantic gorges into the surface of Mars. The study was recently published in the Journal of Volcanology and Geothermal Research.
In recent years, Leone has examined intensively the structure of these canyons and their outlets into the Ares Vallis and the Chryse Planitia, a massive plain on Mars’ low northern latitude. He examined thousands of high-resolution surface images taken by numerous Mars probes, including the latest from the Mars Reconnaissance Orbiter, and which are available on the image databases of the US Geological Survey.
No discernible evidence of erosion by water
His conclusion is unequivocal: “Everything that I observed on those images were structures of lava flows as we know them on Earth,” he emphasises. “The typical indicators of erosion by water were not visible on any of them.” Leone therefore does not completely rules out water as final formative force. Evidence of water, such as salt deposits in locations where water evaporated from the ground or signs of erosion on the alluvial fans of the landslides, are scarce but still existing. “One must therefore ask oneself seriously how Valles Marineris could have been created by water if one can not find any massive and widespread evidence of it.” The Italian volcanologist similarly could find no explanation as to where the massive amounts of water that would be required to form such canyons might have originated.
Source region of lava flows identified
The explanatory model presented by Leone in his study illustrates the formation history from the source to the outlet of the gorge system. He identifies the volcanic region of Tharsis as the source region of the lava flows and from there initial lava tubes stretched to the edge of the Noctis Labyrinthus. When the pressure from an eruption subsided, some of the tube ceilings collapsed, leading to the formation of a chain of almost circular holes, the ‘pit chains’.
When lava flowed again through the tubes, the ceilings collapsed entirely, forming deep V-shaped troughs. Due to the melting of ground and rim material, and through mechanical erosion, the mass of lava carved an ever-deeper and broader bed to form canyons. The destabilised rims then slipped and subsequent lava flows carried away the debris from the landslides or covered it. “The more lava that flowed, the wider the canyon became,” says Leone.
Leone supported his explanatory model with height measurements from various Mars probes. The valleys of the Noctis Labyrinthus manifest the typical V-shape of ‘young’ lava valleys where the tube ceilings have completely collapsed. The upper rims of these valleys, however, have the same height. If tectonic forces had been at work, they would not be on the same level, he says. The notion of water as the formative force, in turn, is undermined by the fact that it would have taken tens of millions of cubic kilometres of water to carve such deep gorges and canyons. Practically all the atmospheric water of all the ages of Mars should have been concentrated only on Labyrinthus Noctis. Moreover, the atmosphere on Mars is too thin and the temperatures too cold. Water that came to the surface wouldn’t stay liquid, he notes: “How could a river of sufficient force and size even form?”
Life less likely
Leone’s study could have far-reaching consequences. “If we suppose that lava formed the Noctis Labyrinthus and the Valles Marineris, then there has always been much less water on Mars than the research community has believed to date,” he says. Mars received very little rain in the past and it would not have been sufficient to erode such deep and large gorges. He adds that the shallow ocean north of the equator was probably much smaller than imagined – or hoped for; it would have existed only around the North Pole. The likelihood that life existed, or indeed still exists, on Mars is accordingly much lower.
Leone can imagine that the lava tubes still in existence are possible habitats for living organisms, as they would offer protection from the powerful UV rays that pummel the Martian surface. He therefore proposes a Mars mission to explore the lava tubes. He considers it feasible to send a rover through a hole in the ceiling of a tube and search for evidence of life. “Suitable locations could be determined using my data,” he says.
Swimming against the current
With his study, the Italian is swimming against the current and perhaps dismantling a dogma in the process. Most studies of the past 20 years have been concerned with the question of water on Mars and how it could have formed the canyons. Back in 1977, a researcher first posited the idea that the Valles Marineris may have been formed by lava, but the idea failed to gain traction. Leone says this was due to the tunnel vision that the red planet engenders and the prevailing mainstream research. The same story has been told for decades, with research targeted to that end, without achieving a breakthrough. Leone believes that in any case science would only benefit in considering other approaches. “I expect a spirited debate,” he says. “But my evidence is strong.”
Note : The above story is based on materials provided by ETH Zurich
Chemical Formula: Cu2Al(AsO4)(OH)4·4H2O Locality: Wheal Gorland, Gwennap, Cornwall, England, UK Name Origin: From the Greek, liros – “pale” and konia – “powder.”
Liroconite is a complex mineral: Hydrated copper aluminium arsenate hydroxide, with the formula Cu2Al(AsO4)(OH)4·4H2O. It is a vitreous monoclinic mineral, colored bright blue to green, often associated with malachite, azurite, olivenite, and clinoclase. It is quite soft, with a Mohs hardness of 2 – 2.5, and has a specific gravity of 2.9 – 3.0.
It was first identified in 1825 in the tin and copper mines of Devon and Cornwall, England. Although it remains quite rare it has subsequently been identified in a variety of locations including France, Germany, Australia, New Jersey and California.
The type locality for Liroconite is Wheal Gorland in St Day, Cornwall in the United Kingdom.
It occurs as a secondary mineral in copper deposits in association with olivenite, chalcophyllite, clinoclase, cornwallite, strashimirite, malachite, cuprite and limonite.
Crystals of putnisite (purple) . Image credit: P. Elliott et al.
The new mineral is named putnisite after Drs Christine and Andrew Putnis from the University of Münster, Germany, for their outstanding contributions to mineralogy.
Putnisite occurs as isolated pseudocubic crystals, up to 0.5 mm in diameter, and is associated with quartz and a near amorphous Cr silicate.
It is translucent, with a pink streak and vitreous lustre. It is brittle and shows one excellent and two good cleavages parallel to {100}, {010} and {001}.
“What defines a mineral is its chemistry and crystallography. By x-raying a single crystal of mineral you are able to determine its crystal structure and this, in conjunction with chemical analysis, tells you everything you need to know about the mineral,” explained Dr Elliott, who, along with colleagues, described putnisite in the Mineralogical Magazine.
“Most minerals belong to a family or small group of related minerals, or if they aren’t related to other minerals they often are to a synthetic compound – but putnisite is completely unique and unrelated to anything.”
Putnisite combines the elements strontium, calcium, chromium, sulfur, carbon, oxygen and hydrogen: SrCa4Cr83+(CO3)8SO4(OH)16•25H2O
The mineral has a Mohs hardness of 1.5–2, a measured density of 2.20 g/cm3 and a calculated density of 2.23 g/cm3. It was discovered during prospecting by a mining company in Western Australia.
“Nature seems to be far cleverer at dreaming up new chemicals than any researcher in a laboratory,” Dr Elliott concluded.
Reference::
P. Elliott et al. 2014. Putnisite, SrCa4Cr83+(CO3)8SO4(OH)16•25H2O, a new mineral from Western Australia: description and crystal structure. Mineralogical Magazine, vol. 78, no. 1, pp. 131-144; DOI: 10.1180/minmag.2014.078.1.10
Note : The above story is based on materials provided by Natali Anderson.
Image showing the remnants of a crater that UAlberta researchers theorize was left by a massive meteorite strike sometime in the last 70 million years. Colour variation shows metres above sea level.
The discovery of an ancient ring-like structure in southern Alberta suggests the area was struck by a meteorite large enough to leave an eight-kilometre-wide crater, producing an explosion strong enough to destroy present-day Calgary, say researchers from the Alberta Geological Survey and University of Alberta.
The first hints about the impact site near the southern Alberta hamlet of Bow City were discovered by a geologist with the Alberta Geological Survey and studied by a U of A team led by Doug Schmitt, Canada Research Chair in Rock Physics.
Time and glaciers have buried and eroded much of the evidence, making it impossible at this point to say with full certainty the ring-like structure was caused by a hypervelocity meteorite impact, but that’s what seismic and geological evidence strongly suggests, said Schmitt, a professor in the Faculty of Science and co-author of a new paper about the discovery.
“We know that the impact occurred within the last 70 million years, and in that time about 1.5 km of sediment has been eroded. That makes it really hard to pin down and actually date the impact.”
Erosion has worn away all but the “roots” of the crater, leaving a semicircular depression eight kilometres across with a central peak. Schmitt says that when it formed, the crater likely reached a depth of 1.6 to 2.4 km—the kind of impact his graduate student Wei Xie calculated would have had devastating consequences for life in the area.
“An impact of this magnitude would kill everything for quite a distance,” he said. “If it happened today, Calgary (200 km to the northwest) would be completely fried and in Edmonton (500 km northwest), every window would have been blown out. Something of that size, throwing that much debris in the air, potentially would have global consequences; there could have been ramifications for decades.”
The impact site was first discovered in 2009 by geologist Paul Glombick, who at the time was working on a geological map of the area for the Alberta Geological Survey, focusing on the shallow subsurface, between zero and 500 metres in depth. Glombick relied on existing geophysical log data from the oil and gas industry when he discovered a bowl-shaped structure. After checking maps of the area dating back to the 1940s, he found evidence of faulting at the surface.
The Alberta Geological Survey contacted the U of A and Schmitt to explore further, peeking into the earth by analyzing seismic data donated by industry. Schmitt’s student, Todd Brown, later confirmed a crater-like structure.
For Glombick, who earned his bachelor’s degree and PhD in geology from the U of A, contributing to such a historic find was a “pretty cool” departure from his regular duties of mapping rock and layers in the shallow subsurface.
“It’s exciting to come across a structure like this. It highlights there’s still a fair amount of unknowns in the shallow subsurface,” he said, noting the oil and gas industry’s geological interests focus deeper underground. “It’s nice to be able to contribute something to the geology of Alberta.”
The research team’s paper about the discovery was published in the journal Meteoritics & Planetary Science in an early online release.
Map:
Note : The above story is based on materials provided by University of Alberta
Chemical Formula: Co2+Co3+2S4 Locality: Bastnäs mines, Riddarhyttan, Västmanland, Sweden. Name Origin: Named after the Swedish botanist, C. Linne (1707-1778).Linnaeite is a cobalt sulfide mineral with the composition Co2+Co3+2S4. It was discovered in 1845 in Västmanland, Sweden, and was named to honor Carl Linnaeus (1707–1778).Linnaeite forms a series with polydymite, Ni+2Ni+32S4. Linnaeite is found in hydrothermal veins with other cobalt and nickel sulfides in many localities around the world
An eroding bluff on the US Great Plains reveals a buried, carbon-rich layer of fossil soil. A team of researchers led by UW-Madison Assistant Professor of geography Erika Marin-Spiotta has found that buried fossil soils contain significant amounts of carbon and could contribute to climate change as the carbon is released through human activities such as mining, agriculutre and deforestation. Credit: Jospeh Mason
Soils that formed on the Earth’s surface thousands of years ago and that are now deeply buried features of vanished landscapes have been found to be rich in carbon, adding a new dimension to our planet’s carbon cycle.
The finding, reported today in the journal Nature Geoscience, is significant as it suggests that deep soils can contain long-buried stocks of organic carbon which could, through erosion, agriculture, deforestation, mining and other human activities, contribute to global climate change.
“There is a lot of carbon at depths where nobody is measuring,” says Erika Marin-Spiotta, a University of Wisconsin-Madison assistant professor of geography and the lead author of the new study. “It was assumed that there was little carbon in deeper soils. Most studies are done in only the top 30 centimeters. Our study is showing that we are potentially grossly underestimating carbon in soils.”
The soil studied by Marin-Spiotta and her colleagues, known as the Brady soil, formed between 15,000 and 13,500 years ago in what is now Nebraska, Kansas and other parts of the Great Plains. It lies up to six-and-a- half meters below the present-day surface and was buried by a vast accumulation of windborne dust known as loess beginning about 10,000 years ago, when the glaciers that covered much of North America began to retreat.
The region where the Brady soil formed was not glaciated, but underwent radical change as the Northern Hemisphere’s retreating glaciers sparked an abrupt shift in climate, including changes in vegetation and a regime of wildfire that contributed to carbon sequestration as the soil was rapidly buried by accumulating loess.
“Most of the carbon (in the Brady soil) was fire derived or black carbon,” notes Marin-Spiotta, whose team employed an array of new analytical methods, including spectroscopic and isotopic analyses, to parse the soil and its chemistry. “It looks like there was an incredible amount of fire.”
The team led by Marin-Spiotta also found organic matter from ancient plants that, thanks to the thick blanket of loess, had not fully decomposed. Rapid burial helped isolate the soil from biological processes that would ordinarily break down carbon in the soil.
Such buried soils, according to UW-Madison geography Professor and study co-author Joseph Mason, are not unique to the Great Plains and occur worldwide.
The work suggests that fossil organic carbon in buried soils is widespread and, as humans increasingly disturb landscapes through a variety of activities, a potential contributor to climate change as carbon that had been locked away for thousands of years in arid and semiarid environments is reintroduced to the environment.
The element carbon comes in many forms and cycles through the environment – land, sea and atmosphere – just as water in various forms cycles through the ground, oceans and the air. Scientists have long known about the carbon storage capacity of soils, the potential for carbon sequestration, and that carbon in soil can be released to the atmosphere through microbial decomposition.
The deeply buried soil studied by Marin-Spiotta, Mason and their colleagues, a one-meter-thick ribbon of dark soil far below the modern surface, is a time capsule of a past environment, the researchers explain. It provides a snapshot of an environment undergoing significant change due to a shifting climate. The retreat of the glaciers signaled a warming world, and likely contributed to a changing environment by setting the stage for an increased regime of wildfire.
“The world was getting warmer during the time the Brady soil formed,” says Mason. “Warm-season prairie grasses were increasing and their expansion on the landscape was almost certainly related to rising temperatures.”
The retreat of the glaciers also set in motion an era when loess began to cover large swaths of the ancient landscape. Essentially dust, loess deposits can be thick—more than 50 meters deep in parts of the Midwestern United States and areas of China. It blankets large areas, covering hundreds of square kilometers in meters of sediment.
This shows a visualization of vibrations inside the Merapi volcano (island of Java) computed with the earthquake simulation software SeisSol. Credit: Alex Breuer (TUM) / Christian Pelties (LMU)
Geophysicists use the SeisSol earthquake simulation software to investigate rupture processes and seismic waves beneath the Earth’s surface. Their goal is to simulate earthquakes as accurately as possible to be better prepared for future events and to better understand the fundamental underlying mechanisms. However, the calculations involved in this kind of simulation are so complex that they push even super computers to their limits.
In a collaborative effort, the workgroups led by Dr. Christian Pelties at the Department of Geo and Environmental Sciences at LMU and Professor Michael Bader at the Department of Informatics at TUM have optimized the SeisSol program for the parallel architecture of the Garching supercomputer “SuperMUC”, thereby speeding up calculations by a factor of five.
Using a virtual experiment they achieved a new record on the SuperMUC: To simulate the vibrations inside the geometrically complex Merapi volcano on the island of Java, the supercomputer executed 1.09 quadrillion floating point operations per second. SeisSol maintained this unusually high performance level throughout the entire three hour simulation run using all of SuperMUC’s 147,456 processor cores.
Complete parallelization
This was possible only following the extensive optimization and the complete parallelization of the 70,000 lines of SeisSol code, allowing a peak performance of up to 1.42 petaflops. This corresponds to 44.5 percent of Super MUC’s theoretically available capacity, making SeisSol one of the most efficient simulation programs of its kind worldwide.
“Thanks to the extreme performance now achievable, we can run five times as many models or models that are five times as large to achieve significantly more accurate results. Our simulations are thus inching ever closer to reality,” says the geophysicist Dr. Christian Pelties. “This will allow us to better understand many fundamental mechanisms of earthquakes and hopefully be better prepared for future events.”
The next steps are earthquake simulations that include rupture processes on the meter scale as well as the resultant destructive seismic waves that propagate across hundreds of kilometers. The results will improve the understanding of earthquakes and allow a better assessment of potential future events.
“Speeding up the simulation software by a factor of five is not only an important step for geophysical research,” says Professor Michael Bader of the Department of Informatics at TUM. “We are, at the same time, preparing the applied methodologies and software packages for the next generation of supercomputers that will routinely host the respective simulations for diverse geoscience applications.”
Note : The above story is based on materials provided by Technische Universitaet Muenchen
Chemical Formula: Cu2(PO4)(OH) Locality: Lubietova (German Livethen), Czechoslovakia. Name Origin: Named after its locality.
Libethenite is a rare copper phosphate hydroxide mineral. It forms striking, dark green orthorhombic crystals. It was discovered in 1823 in Ľubietová, Slovakia and is named after the German name of that locality (Libethen).
GEOMAR researchers specify models for the birth of the youngest world ocean
Pacific, Atlantic and Indian Ocean, with the land masses of the Americas, Europe, Asia, Africa and Australia in between – that’s how we know our earth. From a geologist’s point of view, however, this is only a snapshot. Over the course of the earth’s history, many different continents have formed and split again. In between oceans were created, new seafloor was formed and disappeared again: Plate tectonics is the generic term for these processes.
The Red Sea, where currently the Arabian Peninsula separates from Africa, is one of the few places on earth where the splitting of a continent and the emergence of the ocean can be observed. During a three-year joint project, the Jeddah Transect Project (JTP), researchers at the GEOMAR Helmholtz Centre for Ocean Research Kiel and the King Abdulaziz University (KAU) in Jeddah, Saudi Arabia, have taken a close look at this crack in the earth’s crust by means of seabed mapping, sampling and magnetic modeling. “The findings have shed new light on the early stages of oceanic basins, and they specifically change the school of thought on the Red Sea,” says Dr. Nico Augustin from GEOMAR, lead author of the study. It has now been published in the scientific journal “Earth and Planetary Science Letters”.
It is, and was, undisputed that a continent is stretched and thinned out by volcanic activity before it ruptures and a new ocean basin is formed. The rifting occurs where the greatest stretching takes place. However, the detailed processes during the break-up are debated in research. On the one hand, one needs to better understand the dynamics of our home planet. “On the other hand, most marine oil and gas resources are located near such former fracture zones. This research can therefore also have economic and political implications,” says Professor Colin Devey (GEOMAR), co-author of the study.
Until now, conventional knowledge said that a continent is breaking apart more or less simultaneously along an entire line, and the ocean basin is formed all at once. The Red Sea, however, did not fit into this picture. Here, a model was favored with several smaller fracture zones, lined up one after the other, that would unite gradually, which in turn would lead to a relatively slow emergence of the ocean during a long transition phase. “Our studies show that the Red Sea is not an exception but that it takes its place in line with the other ocean basins,” says Augustin. The previous picture we had of the ocean floor in the Red Sea was simply corrupted by salt glaciers. “The volcanic rocks we recovered are similar to those from other normal mid-ocean ridges,” says co-author Froukje van der Zwan, working on her PhD as part of the JTP.
During the early formation stages of the Red Sea, the area was covered by a very shallow sea that dried up repeatedly. This created thick salt deposits that later on broke apart with the continental crust. Over geologic time periods, salt shows tar-like behavior and begins to flow. “Our new high-resolution seabed maps and magnetic modeling show that the kilometer-thick salt deposits, after the break-up of the Arabian Plate from Africa, flowed like glaciers toward the newly created trench and thus over the oceanic crust due to gravity,” says Augustin. Since these submarine salt glaciers do not cover the rifting zone uniformly over the entire length, the impression of several small fracture zones was created.
The consequences of this discovery are profound: For one, there really seems to be only one single mechanism worldwide for the dispersal of a continent. And secondly, is not yet known how much ocean crust is covered by salt. This questions the previous dating of the opening of the Red Sea. In addition, the volcanically active trench rift zone of the Red Sea, surrounded by salt glaciers, is host of a giant sink filled with a very hot and very salty solution. “Since the sediment in the salt solution is rich in metals, this so-called Atlantis II Deep is also of economic interest,” says co-author Devey. It is quite conceivable that over the course of the earth’s history similar deposits associated with volcanism and salt deposits were created during the opening phase of other oceans. “Thus, our studies help to clarify older research questions. But they also provide starting points for new investigations in all of the oceans,” says Augustin.
Original publication:
Augustin, N., C. W. Devey, F. M. van der Zwan, Peter Feldens, M. Tominaga, R. A. Bantan, T. Kwasnitschka (2014): The rifting to spreading transition in the Red Sea. Earth and Planetary Science Letters, 395, http://dx.doi.org/10.1016/j.epsl.2014.03.047
Note : The above story is based on materials provided by Helmholtz Centre for Ocean Research Kiel (GEOMAR)
This photo shows the approximate location of maximum subsidence in the United States, identified by research efforts of Dr. Joseph F. Poland (pictured). The site is in the San Joaquin Valley southwest of Mendota, Calif. Signs on the pole show approximate altitude of land surface in 1925, 1955, and 1977. Scientists have now found that the groundwater depletion has contributed to rapid uplift of the Sierra Nevada mountains and the California Coast Range as well as affected seismic activity on the San Andreas Fault. Credit: Photo Courtesy USGS.
RENO, Nev. – Like a detective story with twists and turns in the plot, scientists at the University of Nevada, Reno are unfolding a story about the rapid uplift of the famous 400-mile long Sierra Nevada mountain range of California and Nevada.
The newest chapter of the research is being published today in the scientific journal Nature, showing that draining of the aquifer for agricultural irrigation in California’s Central Valley results in upward flexing of the earth’s surface and the surrounding mountains due to the loss of mass within the valley. The groundwater subsidence was found to also correlate with seismic activity on the San Andreas Fault.
University of Nevada, Reno Research Professor Geoff Blewitt also told the story in a presentation at the European Geophysical Sciences Union conference in Vienna, Austria on April 28. The annual EGU General Assembly is the largest and most prominent European geosciences event. It attracts over 11,000 scientists from all over the world.
“We first wrote two years ago about the rapid rise of the Sierra, with its 14,000-foot peaks in the south and 10,000-foot peaks at Lake Tahoe, moving as much as 1 to 3 millimeters per year,” said Blewitt, of the Nevada Bureau of Mines and Geology, a division of the College of Science. “The puzzling results of our earlier research cannot be explained easily by geology alone. We’ve now found that a reason for the rapid uplift may be linked to human activity.”
Over the past 150 years, around 40 trillion gallons of groundwater in California’s Central Valley has been lost through pumping, irrigation and evapotranspiration. That’s roughly equal to all the water in Lake Tahoe, the volume of which can cover the entire state of California in 14 inches of water.
“This massive withdrawal of water has relieved pressure on the Earth’s crust, which is now rebounding upwards in response,” Blewitt said. “This is counter-intuitive to most people, even geologists, who tend to only think that water withdrawal causes subsidence, which is only true in the sediments of the valley from which the water is withdrawn. With the weight of the groundwater missing, the hard-rock crust under the valley is actually rising too.”
The rise is quite fast in geologic time, with these mountain ranges rising by a similar amount each year – about the thickness of a dime – with a cumulative rise over the past 150 years of up to 6 inches, according to the calculations by the team of geophysicists.
Blewitt and colleague Bill Hammond, who run the Nevada Geodetic Laboratory at the University of Nevada, Reno, partnered with the University of Western Washington, the University of California, Berkeley and the University of Ottawa in the research.
“The real importance of this research is that we are demonstrating a potential link between human activity and deformation of the solid Earth, which explains current mountain uplift and the yearly variation in seismicity,” said Colin Amos, assistant professor of geology from Western Washington University and lead author of the Nature article. “These are questions that lots of geologists have been puzzling over, and it’s a real eye opener to think that humans are the ultimate cause.”
The study is based on detailed GPS measurements from California and Nevada between 2007 and 2010. Also working on the study were Pascal Audet of the University of Ottawa and Roland Bürgmann, professor of earth and planetary science at the University of California, Berkeley. The detailed GPS analysis was performed by Hammond and Blewitt with support from the National Science Foundation.
Hammond and Blewitt use data from their Nevada Geodetic Lab and its MAGNET GPS Network, the largest GPS data-processing center in the world, able to process information from about 12,000 stations around the globe continuously, 24/7. The facility measures the shape of the Earth every day using data drawn in from the global network with stations on every continent around the planet, including more than 1,200 stations from the NSF EarthScope Plate Boundary Observatory, as well as stations in space. The space-based radar data comes from the European Space Agency with support from NASA.
“We can sense the long-term flexing of the crust that accompanies trends in climate and related seasonal changes in the Earth’s surface that track yearly precipitation,” Hammond said. “The processing facility at the Nevada Geodetic Laboratory makes it possible to interpret trends in over 500 locations in southern California, needed to measure the centimeter-scale changes these loads produce. It makes it possible for scientists to connect climatic changes to subsidence patterns and the rate of earthquake occurrence.”
“The data is like a gold mine, we keep digging for new discoveries,” he said. “Scientists around the world use it extensively for research such as modeling earthquakes and volcanoes.”
Note : The above story is based on materials provided by University of Nevada, Reno
Leucophoenicite (pink) on zincite Origin: Franklin, Sussex Co., New Jersey, U.S.A. Owner: Lou Perloff Microscopic image
Chemical Formula: Mn7(SiO4)3(OH)2 Locality: Franklin, Sussex Co., New Jersey. Name Origin: From the Greek leukos, “pale” and foinis, “red purple”, in allusion to its color
Leucophoenicite is a mineral with formula Mn7(SiO4)3(OH)2. Generally brown to red or pink in color, the mineral gets its name from the Greek words meaning “pale purple-red”. Leucophoenicite was discovered in the U.S. State of New Jersey and identified as a new mineral in 1899.
Leucophoenicite is normally brown, light purple-red, raspberry-red or pink in color; in thin section it is rose-red to colorless. The name is derived from the Greek words leukos, meaning “pale”, and foinis, meaning “purple-red”, in reference to its common coloring.
Leucophoenicite typically occurs as isolated grains or it has granular massive habit. Crystals of the mineral, which occur rarely, are slender, prismatic, elongated, and striated. The mineral forms in a low pressure, hydrothermal environment or in a contact zone in the veins and skarns of a stratiform Zn-Mn ore body.
Leucophoenicite is a member of the humite group. It has been found in association with barite, barysilite, calcite, copper, franklinite, garnet, glaucochroite, hausmannite, jerrygibbsite, manganosite, pyrochroite, rhodochrosite, sonolite, spessartine, sussexite, tephroite, vesuvianite, willemite, and zincite.
History
Discovery date : 1899 Town of Origin : FRANKLIN, SUSSEX CO., NEW JERSEY Country of Origin: USA
Optical properties
Optical and misc. Properties: Transparent to translucent Refractive Index : from 1,75 to 1,78 Axial angle 2V : 74,5°
Physical Properties
Cleavage: {001} Indistinct Color: Brown, Brown, Violet red, Light red, Dark pink. Density: 3.8 Diaphaneity: Transparent to translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 5.5-6 – Knife Blade-Orthoclase Luminescence: Non-fluorescent. Luster: Vitreous (Glassy) Magnetism: Nonmagnetic
This map shows the distribution of the three volcanoes – the Ka’ena, Wai’anae and Ko’olau – now thought to have made up the region of O’ahu, Hawai’i. Bold dashed lines delineate possible rift zones of the three volcanoes; also shown are the major landslide deposits around O’ahu. Image credit: J. Sinton et al / University of Hawai’i’s School of Ocean and Earth Science and Technology.
As we know it today, O’ahu is the remnants of two volcanoes, Wai’anae and Ko’olau. But extending almost 100 km from the western tip of this island is a large region of shallow bathymetry called the submarine Ka’ena Ridge.
It is that region that has now been recognized to represent a precursor volcano to the island of O’ahu, and on whose flanks the Wai’anae and Ko’olau volcanoes later formed.
Prior to the recognition of Ka’ena Volcano, Wai’anae Volcano was assumed to have been exceptionally large and to have formed an unusually large distance from its next oldest neighbor – Kaua’i.
Prof John Sinton of the University of Hawai’i’s School of Ocean and Earth Science and Technology, who is the lead author of a paper published in the Geological Society of America Bulletin, explained: “both of these assumptions can now be revised: Wai’anae is not as large as previously thought and Ka’ena Volcano formed in the region between Kauai and Wai’anae.”
This image shows how Ka’ena, Wai’anae and Ko’olau overlap. Image credit: J. Sinton et al / University of Hawai’i’s School of Ocean and Earth Science and Technology.
In 2010 scientists documented enigmatic chemistry of some unusual lavas of Wai’anae.
“We previously knew that they formed by partial melting of the crust beneath Wai’anae, but we didn’t understand why they have the isotopic composition that they do. Now, we realize that the deep crust that melted under Waianae is actually part of the earlier Ka’ena Volcano,” Prof Sinton said.
The high-quality bathymetric data showed that Ka’ena Ridge had an unusual morphology.
Prof Sinton’s team then began collecting samples from Ka’ena and Wai’alu submarine Ridges.
The geochemical and age data, along with geological observations and geophysical data confirmed that Ka’ena was not part of Waianae, but rather was an earlier volcanic edifice. Wai’anae must have been built on the flanks of Ka’ena.
“What is particularly interesting is that Ka’ena appears to have had an unusually prolonged history as a submarine volcano, only breaching the ocean surface very late in its history,” Prof Sinton said.
Note : The above story is based on materials provided by GSA Release No. 14-35
Map of the Mackenzie River, second greatest river in North America, that drains to the Arctic Ocean
The Mackenzie River (Slavey language: Deh-Cho, big river or Inuvialuktun: Kuukpak, great river) is the largest and longest river system in Canada, and is exceeded only by the Mississippi River system in North America. It flows through a vast, isolated region of forest and tundra entirely within the country’s Northwest Territories, although its many tributaries reach into four other Canadian provinces and territories. The river’s mainstem runs 1,738 kilometres (1,080 mi) in a northerly direction to the Arctic Ocean, draining a vast area nearly the size of Indonesia. It is the largest river flowing into the Arctic from North America, and with its tributaries is one of the longest rivers in the world.
Rising out of the marshy western end of Great Slave Lake, the Mackenzie River flows generally west-northwest for about 300 km (190 mi), passing the hamlets of Fort Providence and Brownings Landing. At Fort Simpson it is joined by the Liard River, its largest tributary, then swings towards the Arctic, paralleling the Franklin Mountains as it receives the North Nahanni River. The Keele River enters from the left about 100 km (62 mi) above Tulita, where the Great Bear River joins the Mackenzie. Just before crossing the Arctic Circle, the river passes Norman Wells, then continues northwest to merge with the Arctic Red and Peel rivers. It finally empties into the Beaufort Sea, part of the Arctic Ocean, through the vast Mackenzie Delta.
Most of the Mackenzie River is a broad, slow-moving waterway; its elevation drops just 156 metres (512 ft) from source to mouth. It is a braided river for much of its length, characterized by numerous sandbars and side channels. The river ranges from 2 to 5 km (1.2 to 3.1 mi) wide and 8 to 9 m (26 to 30 ft) deep in most parts, and is thus easily navigable except when it freezes over in the winter. However, there are several spots where the river narrows to less than half a kilometre (0.3 mi) and flows quickly, such as at the Sans Sault Rapids at the confluence of the Mountain River and “The Ramparts”, a 40 m (130 ft) deep canyon south of Fort Good Hope.
Watershed
At 1,805,200 square kilometres (697,000 sq mi), the Mackenzie River’s watershed or drainage basin is the largest in Canada, encompassing nearly 20% of the country. From its farthest headwaters at Thutade Lake in the Omineca Mountains to its mouth, the Mackenzie stretches for 4,241 km (2,635 mi) across western Canada, making it the longest river system in the nation and the thirteenth longest in the world. The river discharges more than 325 cubic kilometres (78 cu mi) of water each year, accounting for roughly 11% of the total river flow into the Arctic Ocean. The Mackenzie’s outflow holds a major role in the local climate above the Arctic Ocean with large amounts of warmer fresh water mixing with the cold seawater.
Satellite view of the lower Mackenzie River
Many major watersheds of North America border on the drainage of the Mackenzie River. Much of the western edge of the Mackenzie basin runs along the Continental Divide. The divide separates the Mackenzie watershed from that of the Yukon River and its headstreams the Pelly and Stewart rivers, which flow to the Bering Strait; and the Fraser River and Columbia River systems, both of which run to the Pacific Ocean. Lowland divides in the north distinguish the Mackenzie basin from those of the Anderson, Horton, Coppermine and Back Rivers – all of which empty into the Arctic. Eastern watersheds bordering on that of the Mackenzie include those of the Thelon and Churchill Rivers, both of which flow into Hudson Bay. On the south, the Mackenzie watershed borders that of the North Saskatchewan River, part of the Nelson River system, which empties into Hudson Bay after draining much of south-central Canada.
Through its many tributaries, the Mackenzie River basin covers portions of five Canadian provinces and territories – British Columbia (BC), Alberta, Saskatchewan, and the Yukon and Northwest Territories. The two largest headwaters forks, the Peace and Athabasca Rivers, drain much of the central Alberta prairie and the Rocky Mountains in northern BC then combine into the Slave River at the Peace-Athabasca Delta near Lake Athabasca, which also receives runoff from northwestern Saskatchewan. The Slave is the primary feeder of Great Slave Lake (contributing about 77% of the water); other inflows include the Taltson, Lockhart and Hay Rivers, the latter of which also extends into Alberta and BC. Direct tributaries of the Mackenzie from the west such as the Liard and Peel Rivers carry runoff from the mountains of the eastern Yukon.
The eastern portion of the Mackenzie basin is dominated by vast reaches of lake-studded boreal forest and includes many of the largest lakes in North America. By both volume and surface area, Great Bear Lake is the biggest in the watershed and third largest on the continent, with a surface area of 31,153 km2 (12,028 sq mi) and a volume of 2,236 km3 (536 cu mi). Great Slave Lake is slightly smaller, with an area of 28,568 km2 (11,030 sq mi) and containing 2,088 km3 (501 cu mi) of water, although it is significantly deeper than Great Bear. The third major lake, Athabasca, is less than a third that size with an area of 7,800 km2 (3,000 sq mi). Six other lakes in the watershed cover more than 1,000 km2 (390 sq mi), including the Williston Lake reservoir, the second-largest artificial lake in North America, on the Peace River.
With an average annual flow of 9,910 m3/s (350,000 cu ft/s), the Mackenzie River has the highest discharge of any river in Canada and is the fourteenth largest in the world in this respect. About 60% of the water comes from the western half of the basin, which includes the Rocky, Selwyn, and Mackenzie mountain ranges out of which spring major tributaries such as the Peace and Liard Rivers, which contribute 23% and 27% of the total flow, respectively. In contrast the eastern half, despite being dominated by marshland and large lakes, provides only about 25% of the Mackenzie’s discharge. During peak flow in the spring, the difference in discharge between the two halves of the watershed becomes even more marked. While large amounts of snow and glacial melt dramatically drive up water levels in the Mackenzie’s western tributaries, large lakes in the eastern basin retard springtime discharges. Breakup of ice jams caused by sudden rises in temperature – a phenomenon especially pronounced on the Mackenzie – further exacerbate flood peaks. In full flood, the Peace River can carry so much water that it inundates its delta and backs upstream into Lake Athabasca, and the excess water can only flow out after the Peace has receded.
Geology
As recently as the end of the last glacial period eleven thousand years ago the majority of northern Canada was buried under the enormous continental Laurentide ice sheet. The tremendous erosive powers of the Laurentide and its predecessors, which at maximum extent completely buried the Mackenzie River valley under thousands of meters of ice and flattened the eastern portions of the Mackenzie watershed. When the ice sheet receded for the last time, it left a 1,100 km (680 mi)-long postglacial lake called Lake McConnell, of which Great Bear, Great Slave and Athabasca Lakes are remnants. Significant evidence exists that roughly 13,000 years ago, the channel of the Mackenzie was scoured by one or more massive glacial lake outburst floods unleashed from Lake Agassiz, formed by melting ice west of the present-day Great Lakes. At its peak, Agassiz had a greater volume than all present-day freshwater lakes combined. This is believed to have disrupted currents in the Arctic Ocean and led to an abrupt 1,300-year-long cold temperature shift called the Younger Dryas.
Ecology
The Mackenzie River’s watershed is considered one of the largest and most intact ecosystems in North America, especially in the north. Approximately 63% of the basin – 1,137,000 km2 (439,000 sq mi) – is covered by forest, mostly boreal, and wetlands comprise some 18% of the watershed – about 324,900 km2 (125,400 sq mi). More than 93% of the wooded areas in the watershed are virgin forest. There are fifty-three fish species in the basin, none of them endemic. Most of the aquatic species in the Mackenzie River are descendants of those of the Mississippi River and its tributaries. This anomaly is believed to have been caused by hydrologic connection of the two river systems during the Ice Ages by meltwater lakes and channels.
Fishes in the Mackenzie River proper include the northern pike, some minnows, and lake whitefish, and the river’s shores are lined with sparse vegetation like dwarf birch and willows, as well as numerous peat dogs. Further south the tundra vegetation transitions to black spruce, aspen and poplar forest. Overall, the northern watershed is not very diverse ecologically, due to its cold climate – permafrost underlies about three-quarters of the watershed, reaching up to 100 m (330 ft) deep in the delta region – and meager to moderate rainfall, amounting to about 410 millimetres (16 in) over the basin as a whole. The southern half of the basin, in contrast, includes larger reaches of temperate and alpine forests as well as fertile floodplain and riparian habitat, but is actually home to fewer fish species due to large rapids on the Slave River preventing upstream migration of aquatic species.
Migratory birds use the two major deltas in the Mackenzie River basin – the Mackenzie Delta and the inland Peace-Athabasca Delta – as important resting and breeding areas. The latter is located at the convergence of four major North American migratory routes, or flyways. As recently as the mid-twentieth century, more than 400,000 birds passed through during the spring and up to a million in autumn. Some 215 bird species in total have been catalogued in the delta, including endangered species such as the whooping crane, peregrine falcon and bald eagle. Unfortunately, the construction of W.A.C. Bennett Dam on the Peace River has reduced the seasonal variations of water levels in the delta, causing damage to its ecosystems. Populations of migratory birds in the area have steadily declined since the 1960s.
Note : The above story is based on materials provided by Wikipedia
Chemical Formula: (Na,Ca)2BeSi2(O.OH.F)7 Locality: Langesundfiord district, southern Norway. Name Origin: From the Greek leucos, “white” and phanein, ” to appear” in allusion to the white color
Leucophanite is a sorosilicate mineral with a complex composition, (Na,Ca)2BeSi2(O.OH.F)7. It may contain cerium substituting in the calcium position.
It occurs in pegmatites and alkali igneous complexes as yellow, greenish or white triclinic crystals and has been found in Norway, Quebec and Russia.
It was first described from the Langesundfiord district of southern Norway in 1840. The name is from the Greek leucos for “white” and phanein for “to appear” in allusion to the common white color.
Discovery date: 1840 Town of Origin: LAVEN, LANGESUNDFJORD Country of Origin : NORVEGE
Optical properties
Optical and misc. Properties: Transparent to translucent Refractive Index : from 1,56 to 1,59 Axial angle 2V : 36-50°
Physical Properties
Color: White, Greenish yellow, Yellow, Light green. Density: 2.96 Diaphaneity: Transparent to translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4 – Fluorite Luminescence: Fluorescent, Short UV=pink, Long UV=pink. Luster: Vitreous (Glassy) Streak: white
Australia can no longer lay claim to the origins of the iconic New Zealand kiwi following University of Adelaide research published in the journal Science today showing the kiwi’s closest relative is not the emu as was previously thought.
Instead, the diminutive kiwi is most closely related to the extinct Madagascan elephant bird — a 2-3 metre tall, 275 kg giant. And surprisingly, the study concluded, both of these flightless birds once flew.
A new study by the University of Adelaide’s Australian Centre for Ancient DNA (ACAD), has solved a 150-year-old evolutionary mystery about the origins of the giant flightless “ratite” birds, such as the emu and ostrich, which are found across the southern continents. This group contains some of the world’s largest birds — such as the extinct giant moa of New Zealand and elephant birds of Madagascar.
The different “ratite” species were long thought to have formed as the flightless birds were isolated by the separation of the southern continents over the last 130 million years.
However, ancient DNA extracted from bones of two elephant birds held by the Museum of New Zealand, Te Papa Tongarewa, has revealed a close genetic connection with the kiwi, despite the striking differences in geography, morphology and ecology between the two.
“This result was about as unexpected as you could get,” says Mr Kieren Mitchell, PhD candidate with ACAD, who performed the work. “New Zealand and Madagascar were only ever distantly physically joined via Antarctica and Australia, so this result shows the ratites must have dispersed around the world by flight.”
The results correct previous work by ACAD Director Professor Alan Cooper conducted in the 1990s, which had shown the closest living relatives of the kiwi were the Australian emu and cassowary. “It’s great to finally set the record straight, as New Zealanders were shocked and dismayed to find that the national bird appeared to be an Australian immigrant,” says Professor Cooper. “I can only apologise it has taken so long!”
The team were able to use the elephant bird DNA to estimate when the ratite species had separated from each other.
“The evidence suggests flying ratite ancestors dispersed around the world right after the dinosaurs went extinct, before the mammals dramatically increased in size and became the dominant group,” says Professor Cooper.
“We think the ratites exploited that narrow window of opportunity to become large herbivores, but once mammals also got large, about 50 million years ago, no other bird could try that idea again unless they were on a mammal free island — like the Dodo.”
“We can now see why the evolutionary history of the ratites has been such a difficult problem,” says co-author Professor Mike Lee, of the South Australian Museum and University of Adelaide. “Many of them independently converged on very similar body plans, complicating analysis of their history.”
“We recently found fossils of small kiwi ancestors, which we suggested might have had the power of flight not too long ago,” says co-author Flinders University’s Dr Trevor Worthy. “The genetic results back up this interpretation, and confirm that kiwis were flying when they arrived in New Zealand.
“It also explains why the kiwi remained small. By the time it arrived in New Zealand, the large herbivore role was already taken by the moa, forcing the kiwi to stay small, and become insectivorous and nocturnal.”
Alan Tennyson, Curator of Vertebrates at Te Papa, New Zealand’s national museum, says: “The New Zealand kiwi is an integral part of this country’s culture and heritage. It’s fitting that Te Papa’s scientific collections have been used to resolve the mystery of its origins.”
Journal Reference:
Kieren J. Mitchell, Bastien Llamas, Julien Soubrier, Nicolas J. Rawlence, Trevor H. Worthy, Jamie Wood, Michael S. Y. Lee, Alan Cooper. Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution. Science, 2014 DOI: 10.1126/science.1251981
Note : The above story is based on materials provided by University of Adelaide.
Washington, D.C.—Breaking research news from a team of scientists led by Carnegie’s Ho-kwang “Dave” Mao reveals that the composition of the Earth’s lower mantle may be significantly different than previously thought. These results are to be published by Science.
The lower mantle comprises 55 percent of the planet by volume and extends from 670 and 2900 kilometers in depth, as defined by the so-called transition zone (top) and the core-mantle boundary (below). Pressures in the lower mantle start at 237,000 times atmospheric pressure (24 gigapascals) and reach 1.3 million times atmospheric pressure (136 gigapascals) at the core-mantle boundary.
The prevailing theory has been that the majority of the lower mantle is made up of a single ferromagnesian silicate mineral, commonly called perovskite (Mg,Fe)SiO3) defined through its chemistry and structure. It was thought that perovskite didn’t change structure over the enormous range of pressures and temperatures spanning the lower mantle.
Recent experiments that simulate the conditions of the lower mantle using laser-heated diamond anvil cells, at pressures between 938,000 and 997,000 times atmospheric pressure (95 and 101 gigapascals) and temperatures between 3,500 and 3,860 degrees Fahrenheit (2,200 and 2,400 Kelvin), now reveal that iron bearing perovskite is, in fact, unstable in the lower mantle.
The team finds that the mineral disassociates into two phases one a magnesium silicate perovskite missing iron, which is represented by the Fe portion of the chemical formula, and a new mineral, that is iron-rich and hexagonal in structure, called the H-phase. Experiments confirm that this iron-rich H-phase is more stable than iron bearing perovskite, much to everyone’s surprise. This means it is likely a prevalent and previously unknown species in the lower mantle. This may change our understanding of the deep Earth.
“We still don’t fully understand the chemistry of the H-phase,” said lead author Li Zhang, also of Carnegie. “But this finding indicates that all geodynamic models need to be reconsidered to take the H-phase into account. And there could be even more unidentified phases down there in the lower mantle as well, waiting to be identified.”
Note : The above story is based on materials provided by Carnegie Institution
