This is a tooth recovered from Chesil Beach in Dorset, England, which belonged to a Dakosaurus. Credit: Mark Young and Lorna Steel
A fossilised tooth belonging to a fearsome marine predator has been recorded as the largest of its kind found in the UK, following its recent discovery.
A team of palaeontologists have verified the tooth, which was found near Chesil Beach in Dorset, as belonging to a prehistoric relative of modern crocodiles known as Dakosaurus maximus.
The tooth, which has a broken tip, is approximately 5.5 cm long.
Researchers and curators from University of Edinburgh and the Natural History Museum in London identified the item after it was bought at an online auction by a fossil collector.
Scientists say the circumstances in which the fossil was found were unusual — it was dredged from the sea floor rather than being found on the shore or dug up.
The tooth has been examined and identified by a team of UK palaeontologists and placed in the fossil collection of the Natural History Museum.
Dakosaurus maximus, which grew up to about 4.5 metres long, swam in the shallow seas that covered Europe some 152 million years ago. It belonged to a family of marine animals known as thalattosuchians, relatives of today’s crocodiles.
The unusual shape of the animal’s skull and teeth suggests it ate similar prey to modern-day killer whales. It would have used its broad, short jaws to swallow large fish whole and to bite chunks from larger prey.
The team’s research is published in the scientific journal Historical Biology.
Dr Mark Young, of the University of Edinburgh’s School of Biological Sciences, said: “Given its size, Dakosaurus had very large teeth. However, it wasn’t the top marine predator of its time, and would have swum alongside other larger marine reptiles, making the shallow seas of the Late Jurassic period exceptionally dangerous.”
Note : The above story is based on materials provided by University of Edinburgh.
Chemical Formula: PbFCl Locality: Cromford, near Matlock, Derbyshire. Ancient lead slags at Laurium, Greece. Name Origin: Named from its locality.
Matlockite is a rare lead halide mineral, named after the town of Matlock in Derbyshire, England, where it was first discovered in a nearby mine. Matlockite (chemical formula: PbFCl) gives its name to the matlockite group which consists of rare minerals of a similar structure.
Description
The mineral, a lead fluorochloride (formula PbFCl), was discovered sometime around the early 1800s at Bage Mine at Bolehill near Matlock, together with specimens of phosgenite and anglesite. Although phosgenite was known at this time, it seems likely that matlockite itself remained unappreciated as a new mineral for some fifty years. It was given the name by Greg in 1851. The first mention of Matlockite may have been in Mawe’s Mineralogy of Derbyshire in 1802 in which he gives a detailed description of phosgenite, which is then followed by a mention of a mineral he refers to as “glass lead” – a description which does rather equate to the appearance of matlockite. It is a light, translucent creamy-yellow colour, but heavy in weight having a density that is over 7.1.
A very large specimen 10 cm across, and originating from Derbyshire, exists in the collections of the American Museum of Natural History. A 7 cm specimen can be found in the collection of Derby Museum and Art Gallery.
Matlockite has been reported from a variety of locations since its discovery at the type locality of Derbyshire. The mineral is also found in Tiger, Arizona, Laurium in Greece, a mine near Essen in Germany and near Campiglia in Tuscany. Samples have also been found at locations in South Africa, Peru, Chile, Australia, Austria, France and Italy.
Optical properties
Optical and misc. Properties : Transparent Refractive Index : from 2,00 to 2,14
Physical Properties
Cleavage: {001} Perfect Color: Brownish yellow, Colorless, Green yellow, Dark yellow brown. Density: 7.12 Diaphaneity: Transparent Fracture: Brittle – Uneven – Very brittle fracture producing uneven fragments. Hardness: 2.5-3 – Finger Nail-Calcite Luminescence: Non-Fluorescent. Luster: Adamantine – Pearly Streak: white
Tick carrying spirochetes. Credit: Image courtesy of Oregon State University
Lyme disease is a stealthy, often misdiagnosed disease that was only recognized about 40 years ago, but new discoveries of ticks fossilized in amber show that the bacteria which cause it may have been lurking around for 15 million years — long before any humans walked on Earth.
The findings were made by researchers from Oregon State University, who studied 15-20 million-year-old amber from the Dominican Republic that offer the oldest fossil evidence ever found of Borrelia, a type of spirochete-like bacteria that to this day causes Lyme disease. They were published in the journal Historical Biology.
In a related study, published in Cretaceous Research, OSU scientists announced the first fossil record of Rickettsial-like cells, a bacteria that can cause various types of spotted fever. Those fossils from Myanmar were found in ticks about 100 million years old.
As summer arrives and millions of people head for the outdoors, it’s worth considering that these tick-borne diseases may be far more common than has been historically appreciated, and they’ve been around for a long, long time.
“Ticks and the bacteria they carry are very opportunistic,” said George Poinar, Jr., a professor emeritus in the Department of Integrative Biology of the OSU College of Science, and one of the world’s leading experts on plant and animal life forms found preserved in amber. “They are very efficient at maintaining populations of microbes in their tissues, and can infect mammals, birds, reptiles and other animals.
“In the United States, Europe and Asia, ticks are a more important insect vector of disease than mosquitos,” Poinar said. “They can carry bacteria that cause a wide range of diseases, affect many different animal species, and often are not even understood or recognized by doctors.
“It’s likely that many ailments in human history for which doctors had no explanation have been caused by tick-borne disease.”
Lyme disease is a perfect example. It can cause problems with joints, the heart and central nervous system, but researchers didn’t even know it existed until 1975. If recognized early and treated with antibiotics, it can be cured. But it’s often mistaken for other health conditions. And surging deer populations in many areas are causing a rapid increase in Lyme disease — the confirmed and probable cases of Lyme disease in Nova Scotia nearly tripled in 2013 over the previous year.
The new research shows these problems with tick-borne disease have been around for millions of years.
Bacteria are an ancient group that date back about 3.6 billion years, almost as old as the planet itself. As soft-bodied organisms they are rarely preserved in the fossil record, but an exception is amber, which begins as a free-flowing tree sap that traps and preserves material in exquisite detail as it slowly turns into a semi-precious mineral.
A series of four ticks from Dominican amber were analyzed in this study, revealing a large population of spirochete-like cells that most closely resemble those of the present-day Borrelia species. In a separate report, Poinar found cells that resemble Rickettsia bacteria, the cause of Rocky Mountain spotted fever and related illnesses. This is the oldest fossil evidence of ticks associated with such bacteria.
In 30 years of studying diseases revealed in the fossil record, Poinar has documented the ancient presence of such diseases as malaria, leishmania, and others. Evidence suggests that dinosaurs could have been infected with Rickettsial pathogens.
Humans have probably been getting diseases, including Lyme disease, from tick-borne bacteria as long as there have been humans, Poinar said. The oldest documented case is the Tyrolean iceman, a 5,300-year-old mummy found in a glacier in the Italian Alps.
“Before he was frozen in the glacier, the iceman was probably already in misery from Lyme disease,” Poinar said. “He had a lot of health problems and was really a mess.”
Note : The above story is based on materials provided by Oregon State University.
A Curtin University researcher has shown that ancient volcanic eruptions in Australia 510 million years ago significantly affected the climate, causing the first known mass extinction in the history of complex life.
Published in the journal Geology, Associate Professor Fred Jourdan from Curtin’s Department of Applied Geology, along with colleagues from several Australian and international institutions, used radioactive dating techniques to precisely measure the age of the eruptions of the Kalkarindji volcanic province — where lavas covered an area of more than 2 million square kilometres in the Northern Territory and Western Australia.
Dr Jourdan and his team were able to prove the volcanic province occurred at the same time as the Early-Middle Cambrian extinction from 510-511 million years ago — the first extinction to wipe out complex multicellular life.
“It has been well-documented that this extinction, which eradicated 50 per cent of species, was related to climatic changes and depletion of oxygen in the oceans, but the exact mechanism causing these changes was not known, until now,” Dr Jourdan said.
“Not only were we able to demonstrate that the Kalkarindji volcanic province was emplaced at the exact same time as the Cambrian extinction, but were also able to measure a depletion of sulphur dioxide from the province’s volcanic rocks — which indicates sulphur was released into the atmosphere during the eruptions.
“As a modern comparison, when the small volcano Pinatubo erupted in 1991, the resulting discharge of sulphur dioxide decreased the average global temperatures by a few tenths of a degree for a few years following the eruption.
“If relatively small eruptions like Pinatubo can affect the climate just imagine what a volcanic province with an area equivalent to the size of the state of Western Australia can do.”
The team then compared the Kalkarindji volcanic province with other volcanic provinces and showed the most likely process for all the mass extinctions was a rapid oscillation of the climate triggered by volcanic eruptions emitting sulphur dioxide, along with greenhouse gases methane and carbon dioxide.
“We calculated a near perfect chronological correlation between large volcanic province eruptions, climate shifts and mass extinctions over the history of life during the last 550 million years, with only one chance over 20 billion that this correlation is just a coincidence,” Dr Jourdan said.
Dr Jourdan said the rapid oscillations of the climate produced by volcanic eruptions made it difficult for various species to adapt, ultimately resulting in their demise. He also stressed the importance of this research to better understand our current environment.
“To comprehend the long-term climatic and biological effects of the massive injections of gas in the atmosphere by modern society, we need to recognise how climate, oceans and ecosytems were affected in the past,” he said.
Note : The above story is based on materials provided by Curtin University.
Chemical Formula: Na4Al3Si9O24Cl Locality: Pianura. Near Naples, Italy. Name Origin: Named by von Rath in honor of his wife, Maria Rosa vom Rath (1830-1888).
Marialite is a silicate mineral with a chemical composition of Na4Al3Si9O24Cl if a pure endmember or Na4(AlSi3O8)3(Cl2,CO3,SO4) with increasing meionite content. Marialite is a member of the scapolite group and a solid solution exists between marialite and meionite, the calcium endmember. It is a rare mineral usually used as a collector’s stone. It has a very rare but attractive gemstones and cat’s eye.
Discovery and occurrence
Marialite was first described in 1866 for an occurrence in the Phlegrean Volcanic complex, Campania, Italy. It was named by German mineralogist Gerhard vom Rath for his wife, Maria Rosa vom Rath.
Marialite occurs in regional and contact metamorphism: marble, calcareous gneiss, granulite and greenschist. It also occurs in skarn, pegmatite and hydrothermally altered volcanic rocks. This means that Marialite is formed in high pressure and/or high temperature environments.
History
Discovery date : 1866 Town of Origin : PIANURA, NAPLES, CAMPANIE Country of Origin : ITALIE
Optical properties
Optical and misc. Properties : Transparent to Translucent Refractive Index : from 1,53 to 1,55
Physical Properties
Cleavage: {100} Distinct, {110} Distinct Color: Bluish, Brownish, Colorless, Violet, Greenish. Density: 2.5 – 2.62, Average = 2.56 Diaphaneity: Transparent to Translucent Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 5.5-6 – Knife Blade-Orthoclase Luminescence: Fluorescent, Long UV=strong yellow. Luster: Vitreous – Pearly Streak: white
Some scientists may dream of the chance to pursue their research on another planet. That opportunity isn’t a reality just yet, but PhD student Michaela Musilova got the next best thing – a simulated mission to Mars.
Space suit fitted: check. Helmet secured: check. Radio transmitter attached: check. Air supply pack turned on: check. Time to go into the airlock! While the simulated depressurisation of the airlock is ending, my fellow crewmember and I finish making our plans for the EVA – extra vehicular activity.
I look through the porthole eagerly, in anticipation of stepping out onto the Martian terrain. It’s another sunny day on Mars, even though the temperature is still below zero. It’s a good thing our suits are thick enough to protect us against the cold, but that makes them very heavy: along with the air-supply pack they weigh 15kg.
As I walk over the rolling, red sandy hills of the stunning Martian landscape, I look back at the Mars Desert Research Station (MDRS). It is an analogue (simulation) laboratory – a copy of a planned NASA surface base on Mars – built by the non-profit Mars Society, which works closely with NASA and other international space agencies.
The station is in the high, cold Utah desert, USA, where the environmental conditions, geological features and biological attributes are a good approximation of what we know about those on Mars. It was designed to help people learn about the challenges of living and working on Mars. The Red Planet is considered to be the nearest planet with the resources for humanity to inhabit and then to use as a stepping stone for expansion further into the universe.
I am one of several scientists selected to take part in a total immersion simulation for over two weeks. This means we spend every minute of every day facing the physical and social challenges of life as we would experience it on Mars.
We are here as analogue astronauts, subjected to psychological, nutritional and scientific studies designed by researchers from around the world. These include living with limited amounts of electricity, oxygen, water and dehydrated powder-like astronaut’s food. Crews for simulations are selected to include specialists in different fields of research that would be necessary for the exploration of Mars.
Our crew commander is an aerospace engineer; we have a medical officer, two crew engineers, each specialising in a different aspect of space technology equipment testing; two crew scientists: a geochemist and myself – an astrobiologist and geologist. We also have a film-maker and even a humanoid robot, which we are testing out as a potential crew-member for real Mars missions.
We arrived at MDRS on 18 January 2014 and spent every moment of the simulation in total isolation from our terrestrial lives. The facility became our new home. It is made up of a habitat module nick-named the Hab, a greenhouse called the GreenHab and an observatory. The Hab is a two-storey cylinder-shaped building made to fit atop a heavy-lift space-launch vehicle. It’s only eight metres in diameter, creating a very confined living and working environment.
The common room, on the top floor, also serves as dining room, workstation, kitchen and exercise area. The lower level contains the airlock, laboratories, bathroom and toilet, all crammed into a space the size of my living room. As a consequence, you are almost always within eyeshot and earshot of at least one other person, so, it was really important that the crew could work as a team and get along for a prolonged period despite the lack of privacy.
Each of us has our own scientific experiments to conduct, which involve lab and/or field work in the simulated Martian environment. They include field-testing NASA hardware that extracts hydrogen and oxygen from soil, a technology that could potentially produce breathable air, drinkable water and rocket fuel for a return journey to Earth. If it works, this equipment would dramatically reduce the weight and cost of future space missions.
Our team also carried out simulated surgeries, via Skype, with several research groups around the world including the French/Italian Concordia base in Antarctica. The goal of these ‘tele-surgeries’ was to understand the difficulties faced when medical experts have to direct non-experts in an emergency, with restricted and delayed telecommunications – a situation astronauts travelling to Mars are likely to find themselves in.
One of the engineering projects is on prototype spacesuit glove technology. Our gloves have to be thick but these prototypes are nevertheless designed to feed information to the user’s fingertips about the texture and temperature of what they are holding, giving the astronaut a better awareness of the samples they are handling and the environment around them.
Another engineering project is testing rover cameras and a 3D mapping system similar to the one that will be on the ExoMars rover (scheduled for launch to Mars in 2018).
My own research is on extremophiles: organisms that live in physically or chemically extreme environments and are therefore significant for understanding what kind of life might exist on other planets and to help us develop the technologies to search for it. At MDRS, I am investigating two important questions: whether terrestrial microbes can survive in Mars-like conditions and thus whether there could be similar life on Mars; and whether these extremophiles could be used for terraforming Mars – recreating Earth-like conditions. Without terraforming or some other way of creating conditions for agriculture on Mars we could never properly settle on the Red Planet.
Today, I set out to collect more extremophiles for my experiments in the Hab (and for further analysis during my PhD). I love doing this simulated Martian fieldwork. Regardless of how hard it is to move around in my heavy spacesuit, breathing artificial air in my fishbowl helmet, I am completely absorbed in my role as an analogue astronaut. Walking towards the red Martian hills on the horizon I feel, more than ever, that I am on the path towards my childhood dream of going into space for real.
Single oak pollen grain, SEM image. Credit: Allison Steiner (UM) and Michael Pendleton (Texas A&M)
In the past, many atmospheric scientists believed that pollen particles probably had a negligible effect on climate because they were so big. In recent years, however, as they began to realize that pollen particles were not as sturdy as they once thought, they have been rethinking their old assumptions.
“Pollen can rupture and generate a lot of small, tiny particles,” says Allison Steiner, an associate professor of atmospheric, oceanic and space sciences at the University of Michigan. “They can break pretty easily.”
Moreover, pollen, the same airborne material that wreaks misery during certain seasons in the form of drippy noses and itchy eyes, apparently can have an influence on weather. When big pollen particles break into fine ones, they can take up water vapor in the air to promote the formation of clouds, potentially altering weather systems as a result. Unlike greenhouse gases, which contribute to warming, these fine particles can have a cooling effect.
This is a process that Steiner wants to learn more about, particularly now, when much of the scientific community is devoting considerable attention to the anthropogenic—or human—causes of climate change.
“The impact of pollen in the atmosphere may change weather and it could change our understanding of the climate system,” says the National Science Foundation (NSF)-funded scientist.
“How much is nature contributing?” she adds. “How important will that be in understanding what we will see in the absence of human influences? It’s easier to understand the human causes, but these natural aerosols like pollen are something we don’t understand very well.”
Prior research indicates that when pollen becomes wet, it easily ruptures into very small particles. She wondered whether these small, pollen fragments could, “seed” the creation of clouds.
“If you have water vapor in the atmosphere, it’s hard to form droplets all by itself,” she explains. “But if you have a little particle already there, it’s easy for water to condense on it and grow into a droplet, which enables the formation of cloud droplets.
“Most people think of pollen as being pretty inert in the atmosphere, and it’s not,” she adds. “It’s interacting with the water cycle, and can influence clouds in ways that people hadn’t realized before.”
She and her team are using ground based observation data obtained from across the nation to design a computer algorithm emissions model. The model includes the different types of pollen, and takes into account various conditions that can have an effect on pollen when it enters the atmosphere, for example, rain.
Furthermore, tiny pollen particles can react with radiation. “The models simulate the ability of pollen particles to interact with incoming solar radiation to understand how these particles will affect climate,” she says. By using computer models, she can estimate the effect these particles have on regional climate.
She also has been working in the laboratory of Sarah Brooks, a professor of atmospheric sciences at Texas A&M University, to demonstrate pollen’s effect on cloud formation. Using a cloud condensation nuclei chamber, an instrument that can reproduce the atmospheric conditions that form clouds, they were able to demonstrate that pollen can in fact grow and act as cloud droplets.
“This means that pollen could have an impact on climate,” says Steiner, who conducted the experiments at Texas A & M in the spring. “One thing we are still trying to figure out is how big that effect actually is.”
Steiner is conducting her research under an NSF Faculty Early Career Development (CAREER) award, which she received in 2010. The award supports junior faculty who exemplify the role of teacher-scholars through outstanding research, excellent education, and the integration of education and research within the context of the mission of their organization. NSF is funding her work with $599,940 over five years.
As part of the grant’s educational component, she has worked with middle schools and high schools in Detroit and Ypsilanti. Using the sites and numerous hands-on activities will introduce students to hypothesis development, data collection and analysis, and interpretation, and also will help the pollen emissions model development.
She also plans to integrate elements of the pollen project with University of Michigan undergraduate and graduate programs, as well as form a partnership with the International Centre for Theoretical Physics in Trieste, Italy to train scientists from developing nations on the role of biosphere-atmosphere interactions.
Steiner says she is especially gratified by the response of the young middle school students “who find it a real change to have a college professor come into their classroom on a regular basis,” she says, adding: “It can be a real challenge to make our research relevant for middle-school students. But the students have asked great questions, and we’ve developed some novel hands-on activities that have really helped the students to see how fun and exciting scientific research can be.”
Note : The above story is based on materials provided by National Science Foundation
Chemical Formula: CaAl2(Al2Si2O10)(OH)2 Locality: Corundum mines at Ekaterinurg Distict, Ural Mountains, Russia. Name Origin: From the Greek margaritos – “pearl.”
Margarite is a calcium rich member of the mica group of the phyllosilicates with formula: CaAl2(Al2Si2O10)(OH)2. It forms white to pinkish or yellowish gray masses or thin laminae. It crystallizes in the monoclinic crystal system. It typically has a specific gravity of around 3 and a Mohs hardness of 4. It is translucent with perfect 010 cleavage and exhibits crystal twinning.
It occurs commonly as an alteration product of corundum, andalusite and other aluminous minerals. It has been reported as forming alteration pseudomorphs of chiastolite along with muscovite and paragonite. The margarite in this occurrence forms preferentially along the dark graphite rich inclusions with the chiastolite crystals.
History
Discovery date : 1823 Town of Origin: MT. GREINER, STERZING, TYROL Country of Origin : AUTRICHE
Optical properties
Optical and misc. Properties : Translucent to subtranslucent Refractive Index: from 1,63 to 1,65 Axial angle 2V : 40-67°
Physical Properties
Cleavage: {001} Good Color: White, Gray, Pinkish gray, Yellowish gray. Density: 2.99 – 3.08, Average = 3.03 Diaphaneity: Translucent to subtranslucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4 – Fluorite Luminescence: Fluorescent, Short UV=sky blue, Long UV=strong sky blue. Luster: Pearly Streak: white
Volcanic eruptions across a vast area of what is now Western Australian and the Northern Territory 510 million years ago caused the first known mass extinction of complex life forms.
Curtin University’s Dr Fred Jourdan says it is widely documented that the Early-Middle Cambrian extinction of complex multicellular life was related to changes in climate and depletion of oxygen in the oceans but the exact cause has been unknown until now.
He is part of an international team of scientists that calculated a near perfect chronological correlation between large volcanic eruptions, climate changes and mass extinction over the history of life during the last 550 million years.
The eruptions produced rapid fluctuations in climate making it difficult for species to survive.
The research team’s findings High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the early–Middle Cambrian (Stage 4–5) extinction, have been reported in the journal Geology.
The paper concludes the likely factors responsible for the Early–Middle Cambrian extinction are rapid climate shifts triggered by volcanic eruptions emitting mantle gases sulphur dioxide and greenhouse gases methane and carbon dioxide, either dissolved in the magma or generated by the interaction between magma and evaporite layers and/or oil-rich rocks.
Primative ocean life
Since there was no existing fauna or flora on land during the period, the extinction mechanism must have acted on the oceans.
Life at that time would have included the reef building sponge-like organism Archaeocyathids and Trilobites, the most primitive groups.
Dating techniques
The team used high-precision 40Ar/39Ar and U-Pb mineral dating to measure the age of eruptions in the Kalkarindji volcanic province in the Northern Territory and Western Australia where lavas covered more than two million square kilometres.
Both techniques are based on completely different elements and give the same age for the lavas, which is a strong validation that the age is correct.
Insights into gas emission effect
Dr Jourdan says the research is vital to understanding the long term implications that modern-day massive gas emission into the atmosphere can have on the climate and life.
“I’m talking about greenhouses gases like methane and carbon dioxide which warm the climate and sulphur dioxide which can cool the climate for short periods of time but more relevant to now, can cause acid rains which can wreck ecosystem and massive toxic pollution; part of the irritant pollutants in Beijing come from sulphur dioxide.
“…we can see the effect of those gases on nature by studying the rock record, and we are injecting a massive amount of those into the atmosphere, mostly by burning fossil fuels like coal and oil.”
More information: F. Jourdan, K. Hodges, B. Sell, U. Schaltegger, M.T.D. Wingate, L.Z. Evins, U. Söderlund, P.W. Haines, D. Phillips, and T. Blenkinsop. “High-precision dating of the Kalkarindji large igneous province, Australia, and synchrony with the Early–Middle Cambrian (Stage 4–5) extinction.” Geology, G35434.1, first published on April 24, 2014, DOI: 10.1130/G35434.1
Note : The above story is based on materials provided by Science Network WA
Scientists have found a way to extend the length of time they can use protein molecules to identify tissues like bone and teeth.
Every animal has thousands of proteins in its bones containing information on its species. These proteins make up an almost unique fingerprint that survives long after the animal’s DNA has decomposed.
Scientists can take advantage of this long survival time and use the proteins to try to identify fossils and other ancient tissues like hair and skin. But over time these proteins also begin to break down, which makes it hard to extract the genetic information they hold.
Last year Dr Mike Buckley of the University of Manchester showed that collagen, which contains almost 90 per cent of the proteins in bone, could be used to identify extremely old fossils when his collagen-fingerprinting technique identified a 1.5 million-year-old camel fossil from the high Arctic.
But proteins that aren’t found in collagen have only ever been used to test the genetic information of fossils up to 50,000 years old.
Now Buckley and his PhD student Caroline Wadsworth have managed to use these non-collagenous proteins to test fossils over one million years old.
They found that thousands of non-collagenous proteins – with the potential to be even more informative than collagen – also survive the burial process, and hope to use these in the future to test many older fossils.
Chemical Formula: FeS2 Locality: Common world wide. Name Origin: Arabic or Moorish name for pyrites and similar material of uncertain origin.
The mineral marcasite, sometimes called white iron pyrite, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both structures do have in common that they contain the disulfide S22- ion having a short bonding distance between the sulfur atoms.
The structures differ in how these di-anions are arranged around the Fe2+ cations. Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure.
On fresh surfaces it is pale yellow to almost white and has a bright metallic luster. It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called “cockscombs.”
In marcasite jewellery, pyrite used as a gemstone is termed “marcasite”. That is, marcasite jewellery is made from pyrite not from marcasite. In the late medieval and early modern eras the word “marcasite” meant both pyrite and marcasite (and iron sulfides in general). The narrower, modern scientific definition for marcasite as orthorhombic iron sulfide dates from 1845. The jewellery sense for the word pre-dates this 1845 scientific redefinition. Marcasite in the scientific sense is not used as a gem due to its brittleness.
Occurrence
Marcasite can be formed as both a primary or a secondary mineral. It typically forms under low-temperature highly acidic conditions. It occurs in sedimentary rocks (shales, limestones and low grade coals) as well as in low temperature hydrothermal veins. Commonly associated minerals include pyrite, pyrrhotite, galena, sphalerite, fluorite, dolomite and calcite.
As a primary mineral it forms nodules, concretions and crystals in a variety of sedimentary rock, such as at Dover, Kent, England, where it forms as sharp individual crystals and crystal groups, and nodules (similar to those shown here) in chalk.
As a secondary mineral it forms by chemical alteration of a primary mineral such as pyrrhotite or chalcopyrite.
History
Discovery date : 1845
Optical properties
Optical and misc. Properties : Opaque Reflective Power : 49,1-54,1% (580)
Physical Properties
Cleavage: {010} Indistinct Color: Bronze, Light brass yellow, Tin white. Density: 4.89 Diaphaneity: Opaque Fracture: Uneven – Flat surfaces (not cleavage) fractured in an uneven pattern. Hardness: 6-6.5 – Orthoclase-Pyrite Luminescence: Non-fluorescent. Luster: Metallic Magnetism: Magnetic after heating Streak: gray brownish black
Scientists of the Senckenberg Research Institute in Frankfurt have described the oldest known fossil of a pollinating bird. The well-preserved stomach contents contained pollen from various flowering plants. This indicates that the relationship between birds and flowers dates back at least 47 million years. The fossil comes from the well-known fossil site “Messel Pit.” The study was published today in the scientific journal Biology Letters.
They fly from flower to flower, and with their long, slender bills they transfer the pollen required for the plants’ reproduction. Particularly in the tropics and subtropics, birds, besides insects, serve as the most important pollinators.
“While this process is well known and understood in the present, geological history has offered very little evidence of pollination through birds,” says Dr. Gerald Mayr, head of the Ornithological Section at the Senckenberg Research Institute in Frankfurt. He adds, “there have been occasional hints, such as characteristic bill shapes, that nectarivorous birds occurred in the past, but, so far, there existed no conclusive evidence.”
Now, however, the ornithologist from Frankfurt and his colleague, paleobotanist Dr. Volker Wilde, have found this evidence. In the well-preserved stomach contents of a fossil bird unearthed in the Messel Pit, the scientists discovered fossilized pollen grains.
“This is another discovery that underlines the unique significance of the Messel fossil site,” exclaims a delighted Dr. Wilde. “Not only does the presence of pollen offer direct evidence of the bird’s feeding habits, but it shows that birds already visited flowers as long as 47 million years ago!”
Fossil evidence for the existence of pollinating insects dates back to the Cretaceous period. Until now, however, there had been no information at what time pollination through vertebrates, and birds in particular, came into existence. To date, the oldest indication of an avian pollinator came from the early Oligocene, about 30 million years ago. “But this hummingbird fossil only offers indirect evidence of the existence of nectarivorous birds,” explains Mayr. “Thanks to the excellent state of preservation of the Messel bird, we were able to identify two different types of pollen, which is the first conclusive proof of nectarivory.”
Large numbers of differently sized pollen grains were found in the stomach contents of the completely preserved avian fossil. “Along with the bird’s skeletal anatomy, this indicates that we indeed have the fossil of a nectarivorous bird” explains Wilde.
And the spectacular discovery also suggests another conclusion: If a pollinating bird lived as much as 47 million years ago, it must be assumed that some representatives of the flora at that time had already adapted to this mode of pollination.
“To date, there are no fossil plants from this geological era that offer proof of the existence of ornithophily — i.e., the pollination of flowers through birds,” adds paleobotanist Wilde.
“However, the characteristic traits of bird-pollinated plants, such as red flowers or a lack of scent, do not fossilize,” elaborates Mayr. This lends an even greater importance to discoveries such as the Messel bird to understand the interactions between birds and flowers through geological time.
Note : The above story is based on materials provided by Senckenberg Research Institute and Natural History Museum.
One of Deep-sea limpets, Lepetodrilus nux. Credit: Image courtesy of OIST
A paper by Dr. Masako Nakamura of the OIST Marine Biophysics Unit on the ecology of one of deep-sea limpets called Lepetodrilus nux has been published in the Marine Ecology Progress Series. These deep-sea limpets are conches with shells about 1 cm long. They have been confirmed to live in the long, narrow seabed known as the Okinawa Trough, located at an average of depth of 1000 meters and northwest of the Nansei and Ryukyu Islands. In this paper, three major findings are reported: new limpet habitats in the Okinawa Trough, the process of limpet population formation surmised from their shell length, and limpet reproduction patterns. This is the first study of the life history of limpets living in the Okinawa Trough, including their reproduction and spread, and Dr. Nakamura’s work provides insights into their ecological mechanisms.
In order to understand the spread of marine life, Dr. Nakamura studies benthos, which are animals that are sessile or hardly move in the adult stage. They include deep-sea limpets, reef-building corals, and coral predator crown-of-thorns starfish. In autumn 2011, she boarded a deep-sea research vessel of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) to collect samples of deep-sea benthos from hydrothermal vents in the Okinawa Trough. Hydrothermal vents, where heated, mineral-laden seawater spews from cracks in the ocean crust, are home to various diverse organisms. From the collected samples, Nakamura took some deep-sea limpets back to her laboratory to study their population formation and colonization patterns. She did this by examining two characteristics: shell length and distribution pattern. Each sample was carefully measured to examine the time the sample has lived in a colony. The longer the shell length, the longer the inhabitance.
To understand the distribution patterns, Nakamura studies the fertilization process of limpets. Through microscopic observation of tissue sections from limpet gonads, she confirmed the stages of egg and sperm development. While limpets have distinct male and female sexes, the female has a bag-like organ called a spermatheca to store sperms for internal fertilization. Nakamura also discovered that eggs and sperms in various stages of maturity coexist simultaneously within the limpet’s genital glands. The limpets undergo a continual fertilization process in which each egg is spawned when it reaches maturity. This is different from coral fertilization, in which numerous mature eggs and sperms are released simultaneously and fertilized in the water. Fertilized limpet eggs released into the sea drift through the larval stage of growth, eventually finding home and adhering to the seabed to join a benthos community. The OIST Marine Biophysics Unit to which Dr. Nakamura belongs also studies ocean currents, which have considerable impact on the spread of benthic larvae. The team is trying to understand life history traits of benthos at the initial stage and the influence of ocean currents in order to find out how these organisms expand their habitat and respond to environmental changes.
Dr. Nakamura goes out on the water and observes marine organisms first hand. This approach is rooted in her belief that certain things can only be understood through observation of their natural state, and that the information obtained through these observations should be valued. “I would like to pass along to the next generation of researchers a diligent field research approach to understand ecosystems,” Dr. Nakamura said. By accumulating the understanding of the ecology of small marine organisms, she hopes to deepen an understanding of the spread of life in the entire ocean.
Note : The above story is based on materials provided by Okinawa Institute of Science and Technology – OIST.
Chemical Formula: MnO(OH) Locality: Ilfeld, Harz, Germany Name Origin: Named after its chemical composition.
Manganite is a mineral. Its composition is manganese oxide-hydroxide, MnO(OH), crystallizing in the monoclinic system (pseudo-orthorhombic). Crystals of manganite are prismatic and deeply striated parallel to their length; they are often grouped together in bundles. The color is dark steel-grey to iron-black, and the luster brilliant and submetallic. The streak is dark reddish-brown. The hardness is 4, and the specific gravity is 4.3. There is a perfect cleavage parallel to the brachypinacoid, and less-perfect cleavage parallel to the prism faces. Twinned crystals are not infrequent.
The mineral contains 89.7% manganese sesquioxide; it dissolves in hydrochloric acid with evolution of chlorine.
Occurrence
Manganite occurs with other manganese oxides in deposits formed by circulating meteoric water in the weathering environment in clay deposits and laterites. It forms by low temperature hydrothermal action in veins in association with calcite, barite, and siderite. Often associated with pyrolusite, braunite, hausmannite and goethite.
Manganite occurs in specimens exhibiting good crystal form at Ilfeld in the Harz Mountains of Germany, where the mineral occurs with calcite and barite in veins traversing porphyry. Crystals have also been found at Ilmenau in Thuringia, Neukirch near Sélestat in Alsace (newkirkite), Granam near Towie in Aberdeenshire, and in Upton Pyne near Exeter, UK and Negaunee, Michigan, United States, and in the Pilbarra of Western Australia. Good crystals have also been found at Atikokan, Ontario and Nova Scotia, Canada. As an ore of manganese it is much less abundant than pyrolusite or psilomelane.
Although described with various other names as early as 1772, the name manganite was first applied in a publication by W. Haidinger in 1827.
History
Discovery date : 1827 Town of Origin : ILFELD,HARZ Country of Origin: ALLEMAGNE
Optical properties
Optical and misc. Properties : Opaque Reflective Power : ~17%
Physical Properties
Cleavage: {010} Perfect Color: Black, Gray, Grayish black. Density: 4.3 – 4.4, Average = 4.34 Diaphaneity: Opaque Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4 – Fluorite Luminescence: Non-fluorescent. Luster: Sub Metallic Magnetism: Nonmagnetic Streak: dark brown
A sample of ancient rock from the Acasta Gneiss Complex in the Northwest Territories. Credit: Image courtesy of University of Alberta
It looks like just another rock, but what Jesse Reimink holds in his hands is a four-billion-year-old chunk of an ancient protocontinent that holds clues about how Earth’s first continents formed.
The University of Alberta geochemistry student spent the better part of three years collecting and studying ancient rock samples from the Acasta Gneiss Complex in the Northwest Territories, part of his PhD research to understand the environment in which they formed.
“The timing and mode of continental crust formation throughout Earth’s history is a controversial topic in early Earth sciences,” says Reimink, lead author of a new study in Nature Geoscience that points to Iceland as a solid comparison for how the earliest continents formed.
Continents today form when one tectonic plate shifts beneath another into Earth’s mantle and cause magma to rise to the surface, a process called subduction. It’s unclear whether plate tectonics existed 2.5 billion to four billion years ago or if another process was at play, says Reimink.
One theory is the first continents formed in the ocean as liquid magma rose from Earth’s mantle before cooling and solidifying into a crust.
Iceland’s crust formed when magma from the mantle rises to shallow levels, incorporating previously formed volcanic rocks. For this reason, Reimink says Iceland is considered a theoretical analogue on early Earth continental crust formation.
Ancient rocks 3.6 to four billion years old
A sample of ancient rock from the Acasta Gneiss Complex in the Northwest Territories
Working under the supervision of co-author Tom Chacko, Reimink spent his summers in the field collecting rock samples from the Acasta Gneiss Complex, which was discovered in the 1980s and found to contain some of Earth’s oldest rocks, between 3.6 and four billion years old. Due to their extreme age, the rocks have undergone multiple metamorphic events, making it difficult to understand their geochemistry, Reimink says.
Fortunately, a few rocks — which the research team dubbed “Idiwhaa” meaning “ancient” in the local Tlicho dialect — were better preserved. This provided a “window” to see the samples’ geochemical characteristics, which Reimink says showed crust-forming processes that are very similar to those occurring in present-day Iceland.
“This provides the first physical evidence that a setting similar to modern Iceland was present on the early Earth.”
These ancient rocks are among the oldest samples of protocontinental crust that we have, he adds, and may have helped jump-start the formation of the rest of the continental crust.
Reimink, who came to the U of A to work with Chacko, says the university’s lab resources are “second to none,” particularly the Ion Microprobe facility within the Canadian Centre for Isotopic Microanalysis run by co-author Richard Stern, which was instrumental to the discovery.
“That lab is producing some of the best data of its kind in the world. That was very key to this project.”
Note : The above story is based on materials provided by University of Alberta.
Illustration of Earth as seen from the moon. The gravitational tug-of-war between Earth and the moon raises a small bulge on the moon. The position of this bulge shifts slightly over time. Credit: NASA’s Goddard Space Flight Center
Scientists combined observations from two NASA missions to check out the moon’s lopsided shape and how it changes under Earth’s sway — a response not seen from orbit before.
The team drew on studies by NASA’s Lunar Reconnaissance Orbiter, which has been investigating the moon since 2009, and by NASA’s Gravity Recovery and Interior Laboratory, or GRAIL, mission. Because orbiting spacecraft gathered the data, the scientists were able to take the entire moon into account, not just the side that can be observed from Earth.
“The deformation of the moon due to Earth’s pull is very challenging to measure, but learning more about it gives us clues about the interior of the moon,” said Erwan Mazarico, a scientist with the Massachusetts Institute of Technology in Cambridge, Mass., who works at NASA’s Goddard Space Flight Center in Greenbelt, Md.
The lopsided shape of the moon is one result of its gravitational tug-of-war with Earth. The mutual pulling of the two bodies is powerful enough to stretch them both, so they wind up shaped a little like two eggs with their ends pointing toward one another. On Earth, the tension has an especially strong effect on the oceans, because water moves so freely, and is the driving force behind tides.
Earth’s distorting effect on the moon, called the lunar body tide, is more difficult to detect, because the moon is solid except for its small core. Even so, there is enough force to raise a bulge about 20 inches (51 centimeters) high on the near side of the moon and similar one on the far side.
The position of the bulge actually shifts a few inches over time. Although the same side of the moon constantly faces Earth, because of the tilt and shape of the moon’s orbit, the side facing Earth appears to wobble. From the moon’s viewpoint, Earth doesn’t sit motionless but moves around within a small patch of sky. The bulge responds to Earth’s movements like a dance partner, following wherever the lead goes.
“If nothing changed on the moon — if there were no lunar body tide or if its tide were completely static — then every time scientists measured the surface height at a particular location, they would get the same value,” said Mike Barker, a Sigma Space Corporation scientist based at Goddard and co-author of the new study, which is available online in Geophysical Research Letters.
A few studies of these subtle changes were conducted previously from Earth. But not until LRO and GRAIL did satellites provide enough resolution to see the lunar tide from orbit.
To search for the tide’s signature, the scientists turned to data taken by LRO’s Lunar Orbiter Laser Altimeter, or LOLA, which is mapping the height of features on the moon’s surface. The team chose spots that the spacecraft has passed over more than once, each time approaching along a different flight path. More than 350,000 locations were selected, covering areas on the near and far sides of the moon.
The researchers precisely matched measurements taken at the same spot and calculated whether the height had risen or fallen from one satellite pass to the next; a change indicated a shift in the location of the bulge.
A crucial step in the process was to pinpoint exactly how far above the surface LRO was located for each measurement. To reconstruct the spacecraft’s orbit with sufficient accuracy, the researchers needed the detailed map of the moon’s gravity field provided by the GRAIL mission.
“This study provides a more direct measurement of the lunar body tide and much more comprehensive coverage than has been achieved before,” said John Keller, LRO project scientist at Goddard.
The good news for lunar scientists is that the new results are consistent with earlier findings. The estimated size of the tide confirmed the previous measurement of the bulge. The other value of great interest to researchers is the overall stiffness of the moon, known as the Love number h2, and this was also similar to prior results.
Having confirmation of the previous values — with significantly smaller errors than before — will make the lunar body tide a more useful piece of information for scientists.
“This research shows the power of bringing together the capabilities of two missions. The extraction of the tide from the LOLA data would have been impossible without the gravity model of the moon provided by the GRAIL mission,” said David Smith, the principal investigator for LRO’s LOLA instrument and the deputy principal investigator for the GRAIL mission. Smith is affiliated with Goddard and the Massachusetts Institute of Technology.
Note : The above story is based on materials provided by NASA/Goddard Space Flight Center.
Chemical Formula: Fe2+Fe3+2O4 Locality: Many localities and environments world wide. Name Origin: Named for Magnes, a Geek shepherd, who discovered the mineral on Mt, Ida, He noted that the nails of his shoe and the iron ferrule of his staff clung to a rock.
Magnetite is a mineral, one of the three common naturally occurring iron oxides (chemical formula Fe3O4) and a member of the spinel group. Magnetite is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient people first noticed the property of magnetism.
Small grains of magnetite occur in almost all igneous and metamorphic rocks. Magnetite is black or brownish-black with a metallic luster, has a Mohs hardness of 5–6 and a black streak.
The chemical IUPAC name is iron(II,III) oxide and the common chemical name is ferrous-ferric oxide.
History
Discovery date : 1845 Town of Origin : MAGNESIA, THESSALIE Country of Origin : GRECE
Optical properties
Optical and misc. Properties : Opaque Reflective Power : ~21%
Physical Properties
Cleavage: None Color: Grayish black, Iron black. Density: 5.1 – 5.2, Average = 5.15 Diaphaneity: Opaque Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces. Hardness: 5.5-6 – Knife Blade-Orthoclase Luminescence: Non-fluorescent. Luster: Metallic Magnetism: Naturally strong Streak: black
Scientists have used a highly sensitive, high-resolution X-ray scanning technique to detect minute quantities of chemicals associated with bone healing in 150-million-year-old dinosaur bones.
They looked in cracks, fractures and breaks in the ancient remains, and found traces of copper, zinc and strontium, which are essential for enzymes involved with bone maintenance, repair and healing.
As well as shedding light on the differences between normal and healed bone, the findings give the first chemical clues to how the dinosaurs’ bones may have healed when they were injured.
They also suggest that many predatory dinosaurs may have recovered from the impact of massive trauma, which would likely kill you or me.
The findings are published in Journal of the Royal Society Interface.
‘It seems dinosaurs evolved a splendid suite of defence mechanisms to help regulate the healing and repair of injuries. Not a lot is known about the biochemistry of healing in extinct animals. So, the ability to diagnose such processes some 150 million years later might well shed light on how we can use Jurassic chemistry in the 21st century,’ says Dr Phil Manning of the University of Manchester, one of the study’s co-authors.
Fossilised bones sometimes show evidence of trauma, sickness and subsequent signs healing. Working out what happened to them usually relies on scientists slicing through ancient, valuable specimens to analyse them.
Manning and colleagues from UK and US universities realised that looking at so-called chemical signatures in the bones could uncover details about how they healed.
‘This is because the body uses a distinct suite of trace-metal co-ordinated enzymes to repair bones,’ explains Manning.
‘Copper-based enzymes are associated with forming calluses. The second stage of bone repair involves zinc-containing enzymes, which promotes bone growth. And the final stage to check all the work done is good involves an enzyme that contains strontium,’ he adds.
‘So if you’re imaging a healed fracture, you’ll find trace amounts of strontium evenly distributed along the healed bone. But if it’s still healing, there’ll be higher concentrations of zinc.’
These elements make up much less than one per cent of our entire bodies, which means trying to find them in 150-million-year-old fossils is a big ask.
The interdisciplinary team based at the University of Manchester used both the Stanford Synchrotron Radiation Light Source and Diamond Light Source to analyse a bone from a theropod dinosaur called Allosaurus fragilis.
The predatory Allosaurus, which means ‘different lizard’, lived 155 to 150 million years ago during the late Jurassic Period. It was a member of a group of vertebrates called the archosaurs, whose modern members include the crocodiles and birds.
The researchers also used the Stanford synchrotron to analyse a bone from a living archosaur, the turkey vulture.
‘Theropods are a logical study group as they are more closely related to the most diverse group of extant archosaurs, the birds,’ explain the authors.
Synchrotron particle accelerators act like a giant microscope, harnessing the power of electrons to produce light brighter than a billion suns to study anything from jet engines to viruses and vaccines.
The team used extremely bright light produced by the two particle accelerators to find minute traces of zinc, copper and strontium in the bones.
‘You can only detect such chemistry using a synchrotron, because this technique permits you to exactly image the relationship of each atom to its surrounding elements. This allows you to identify if the element was part of the bone-healing process, or if it came from the environment in which the bone became fossilised,’ says Manning.
When they compared the chemical signatures in the dinosaur and turkey vulture specimens, they expected them to be fairly similar.
But they found that the dinosaur bone revealed signs of fracture healing that are more reminiscent of that of modern reptiles like crocodiles or alligators.
‘It is quite possible you’ve got a reptilian-style repair mechanism combined with elevated metabolism, like that you’d find in alligators and birds respectively. So you’ve got a double whammy in a good way. If you suffer massive trauma, you’ve got the perfect set-up to survive it,’ says Manning.
‘Bones doesn’t form scar tissue, like a scratch to your skin, so the body has to completely reform new bone following the same stages that occurred at the skeleton grew in the first place. The means we are able to tease out the chemistry of bone development through such pathological studies,’ says Jennifer Anné, PhD student at the University of Manchester, first author of the study.
‘You’re basically seeing a biological process preserved in the sands of time,’ adds Manning.
More Information :
Jennifer Anné, Nicholas P. Edwards, Roy A. Wogelius, Allison R. Tumarkin-Deratzian, William I. Sellers, Arjen van Veelen, Uwe Bergmann, Dimosthensis Sokaras, Roberto Alonso-Mori, Konstantin Ignatyev, Victoria M. Egerton and Phillip L. Manning, Synchrotron imaging reveals bone healing and remodelling strategies in extinct and extant vertebrates, Journal of the Royal Society Interface, published 7th May 2014, http://dx.doi.org/10.1098/rsif.2014.0277
This is one of many icebergs that sheared off the continent and ended up in the Scotia Sea. Credit: Michael Weber, University of Cologne
A new study has found that the Antarctic Ice Sheet began melting about 5,000 years earlier than previously thought coming out of the last ice age – and that shrinkage of the vast ice sheet accelerated during eight distinct episodes, causing rapid sea level rise.
The international study, funded in part by the National Science Foundation, is particularly important coming on the heels of recent studies that suggest destabilization of part of the West Antarctic Ice Sheet has begun.
Results of this latest study are being published this week in the journal Nature. It was conducted by researchers at University of Cologne, Oregon State University, the Alfred-Wegener-Institute, University of Hawaii at Manoa, University of Lapland, University of New South Wales, and University of Bonn.
The researchers examined two sediment cores from the Scotia Sea between Antarctica and South America that contained “iceberg-rafted debris” that had been scraped off Antarctica by moving ice and deposited via icebergs into the sea. As the icebergs melted, they dropped the minerals into the seafloor sediments, giving scientists a glimpse at the past behavior of the Antarctic Ice Sheet.
Periods of rapid increases in iceberg-rafted debris suggest that more icebergs were being released by the Antarctic Ice Sheet. The researchers discovered increased amounts of debris during eight separate episodes beginning as early as 20,000 years ago, and continuing until 9,000 years ago.
The melting of the Antarctic Ice Sheet wasn’t thought to have started, however, until 14,000 years ago.
“Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last ice age, that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size,” said lead author Michael Weber, a scientist from the University of Cologne in Germany.
“The sediment record suggests a different pattern – one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation,” Weber added.
The research also provides the first solid evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of very rapid sea level rise that began some 14,500 years ago, according to Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.
The largest of the eight episodic pulses outlined in the new Nature study coincides with meltwater pulse 1A.
“During that time, the sea level on a global basis rose about 50 feet in just 350 years – or about 20 times faster than sea level rise over the last century,” noted Clark, a professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “We don’t yet know what triggered these eight episodes or pulses, but it appears that once the melting of the ice sheet began it was amplified by physical processes.”
The researchers suspect that a feedback mechanism may have accelerated the melting, possibly by changing ocean circulation that brought warmer water to the Antarctic subsurface, according to co-author Axel Timmermann, a climate researcher at the University of Hawaii at Manoa.
“This positive feedback is a perfect recipe for rapid sea level rise,” Timmermann said.
Some 9,000 years ago, the episodic pulses of melting stopped, the researchers say.
“Just as we are unsure of what triggered these eight pulses,” Clark said, “we don’t know why they stopped. Perhaps the sheet ran out of ice that was vulnerable to the physical changes that were taking place. However, our new results suggest that the Antarctic Ice Sheet is more unstable than previously considered.”
Today, the annual calving of icebergs from Antarctic represents more than half of the annual loss of mass of the Antarctic Ice Sheet – an estimated 1,300 to 2,000 gigatons (a gigaton is a billion tons). Some of these giant icebergs are longer than 18 kilometers.
More information: Paper: Millennial-scale variability in Antarctic ice-sheet discharge during the last deglaciation, dx.doi.org/10.1038/nature13397
Note : The above story is based on materials provided by Oregon State University
Chemical Formula: MgCO3 Locality: Magnisía (Magnesia) Prefecture, Thessalia (Thessaly) Department, Greece Name Origin: Named after its chemical composition.
Magnesite is a mineral with the chemical formula MgCO3 (magnesium carbonate). Mixed crystals of iron II carbonate and magnesite (mixed crystals known as ankerite) possess a layered structure: monolayers of carbonate groups alternate with magnesium monolayers as well as iron II carbonate monolayers. Manganese, cobalt and nickel may also occur in small amounts.
Occurrence
Magnesite occurs as veins in and an alteration product of ultramafic rocks, serpentinite and other magnesium rich rock types in both contact and regional metamorphic terrains. These magnesites often are cryptocrystalline and contain silica in the form of opal or chert.
Magnesite is also present within the regolith above ultramafic rocks as a secondary carbonate within soil and subsoil, where it is deposited as a consequence of dissolution of magnesium-bearing minerals by carbon dioxide within groundwaters.
History
Discovery date : 1808 Town of Origin : MAGNESIA, THESSALIE Country of Origin : GRECE
Optical properties
Optical and misc. Properties : Transparent to translucent to opaque Refractive Index : from 1,50 to 1,70
Physical Properties
Cleavage: {1011} Perfect, {1011} Perfect, {1011} Perfect Color: Colorless, White, Grayish white, Yellowish white, Brownish white. Density: 3 Diaphaneity: Transparent to translucent to opaque Fracture: Brittle – Conchoidal – Very brittle fracture producing small, conchoidal fragments. Hardness: 4 – Fluorite Luminescence: Fluorescent, Short UV=blue white, Long UV=bright blue white. Luster: Vitreous (Glassy) Streak: white
