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20 Things You Didn’t Know About Crystals

  1. It’s all about the rhythm: Crystals are repeating, three-dimensional arrangements of atoms, ions, or molecules.
  2. Almost any solid material can crystallize—even DNA. Chemists from New York University, Purdue University, and the Argonne National Laboratory recently created DNA crystals large enough to see with the naked eye. The work could have applications in nanoelectronics and drug development.
  3. One thing that is not a crystal: leaded “crystal” glass, like the vases that so many newlyweds dread. (Glass consists of atoms or molecules all in a jumble, not in the well-patterned order that defines a crystal.)
  4. The oldest known pieces of our planet’s surface are 4.4-billion-year-old zircon crystals from the Jack Hills of western Australia.
  5. The center of the earth was once thought to be a single, 1,500-mile-wide iron crystal. Seismic studies now show that the inner core is not a single solid but perhaps an aggregate of smaller crystals.
  6. Tiny silicate crystals, which need high temperatures to form, have been found inside icy comets from the solar system’s distant, chilly edges. Powerful flares from the sun may have provided the necessary heat.
  7. In Chihuahua, 
Mexico, a limestone cavern 1,000 feet below the surface contains the largest crystals in the world: glittering gypsum formations up to 6 feet in diameter and 36 feet long, weighing as much as 55 tons.
  8. You may be sitting in a gypsum cave right now: It is a primary component of drywall.
  9. Are the streets of New York paved with gold? No, but the bedrock schist beneath them is studded with opal, beryl, chrysoberyl, garnet, and three kinds of tourmaline.
  10. In 1885 a garnet weighing nearly 10 pounds was discovered beneath 35th Street near Broadway, close to today’s Macy’s store. According to urban lore, it was unearthed either during subway construction or by a laborer digging a sewer.
  11. Cheaper by the pound: The so-called Subway Garnet was sold within a day, reportedly for $100—just $2,300 in today’s dollars.
  12. The unit of measure for gemstones had humble beginnings. “Carat” comes from the Greek keration, or “carob bean,” which was used as a standard for weighing small quantities. It is equivalent to 200 milligrams, or about 0.007 ounce.
  13. When Richard Burton bought Elizabeth Taylor the heart-shaped Taj-Mahal diamond, he is said to have bragged, “It has so many carats, it’s almost a turnip.”
  14. A “fancy intense pink” diamond recently set a world record when it was purchased at auction for $46 million by a London jeweler.
  15. The Cullinan diamond is the largest known gem diamond—or, actually, was. It weighed 3,106 carats, or nearly a pound and a half, when it was discovered in South Africa in 1905, but it has since been cut into more than 100 stones.
  16. The Cullinan stones, all flawless, are now part of the British Regalia. The largest, a 530-carat behemoth, is set in one of the British royal scepters.
  17. For the rest of us, there is crystallized sodium chloride, otherwise known as salt. We are literally awash in it: If the water were evaporated from the world’s oceans, we’d be left with 4.5 million cubic miles of salt, equivalent to a cube measuring 165 miles on each side.
  18. Another crystal for commoners: sugar. Each American eats an average of more than 130 pounds of it per year.
  19. As if sugar’s ties to obesity and tooth decay weren’t enough, new research out of Imperial College London suggests that it contributes to high blood pressure, too.
  20. Snow is near-pure crystallized water, but when it collects on the ground it acts as a reservoir for atmospheric pollutants such as mercury and soot. So you probably shouldn’t eat the white snow either.

Note: The above post is reprinted from materials provided by Discover Magazine. The original article was written by Rebecca Coffey.

Alaska volcano Q&A

This photo taken Dec. 21, 2016 and provided by Lynda Lybeck Robinson shows the Bogoslof Volcano erupting in the Aleutian Islands, Alaska. The active Alaska volcano, which has erupted 10 times since mid-December and is located about 850 miles southwest of Anchorage, erupted again Thursday, Jan. 5, 2017, this time sending a cloud of ash and ice 35,000 feet in the air. Credit: Lynda Lybeck Robinson via AP

A remote volcano in Alaska’s Aleutian Islands has erupted 10 times in less than a month, and experts say more eruptions are possible.

Bogoslof volcano has sent up ash clouds that have reached as high as 35,000 feet. Here are answers to questions on why volcanoes in Alaska erupt so often and the dangers they present:

HOW MANY VOLCANOES ARE IN ALASKA?

The Alaska Volcano Observatory, a joint program of the U.S. Geological Survey and the University of Alaska Fairbanks, says 90 volcanoes have been active within the last 10,000 years—and could erupt again. More than 50 have been active since about 1760, when record-keeping begin.

Like Bogoslof, most are on the 1,550-mile-long Aleutian Arc, which forms the northern portion of the Pacific “Ring of Fire,” a horseshoe shape zone around the Pacific Ocean of frequent earthquakes and volcanic eruptions triggered by the subduction of an oceanic plate beneath continental plates.

HOW OFTEN DO ALASKA VOLCANOES ERUPT?

Regularly. Pavlof Volcano sent up ash clouds in 2013. Cleveland volcano blew in December 2011. Redoubt volcano 100 miles southwest of Anchorage blew in March 2009, dropping ash during the medals ceremony for the U.S. alpine ski championships at Alyeska Resort in Girdwood. Some volcanoes erupt and spit out additional ash intermittently for weeks, as Bogoslof seems to be doing.

The Alaska Volcano Observatory, formed in response to the 1986 eruption of Mount Augustine, has tools to predict eruptions. As magma moves beneath a volcano before an eruption, it often generates earthquakes, swells the surface of a mountain and increases the gases emitted. The observatory samples gases, measures earthquake activity and watches for landscape deformities.

The observatory uses mathematical models to forecast how fast ash particles will be transported in the atmosphere and where ash could fall. The observatory runs the models when it detects that a volcano might erupt, and updates them when they blow.

WHY ARE ALASKA VOLCANOES DANGEROUS?

Volcanoes in Hawaii ooze lava. Volcanoes in Alaska tend to explode.

Instead of a red river of lava, Alaska volcanoes typically shoot ash up to 50,000 feet, or more than nine miles, into the jet stream.

That ash is not the kind you left after a campfire. Instead, it’s an abrasive kind of rock fragment. The particulate has jagged edges and has been used as an industrial abrasive to polish metals.

Particulate can injure skin, eyes and breathing passages. The young, the elderly and people with respiratory problems are especially susceptible. Ash under a windshield wiper can scratch glass. However, most volcanoes are far from communities and ash fall requiring breathing masks or new air filters on a car is infrequent.

WHAT DOES IT DO TO AIRCRAFT?

USGS geophysicist John Power once likened flying through an ash cloud to flying into a sandblaster.

Ash can scrape the moving parts of jet engines such as turbine blades. However, ash on hot parts of a jet engine is potentially more dangerous, according to the observatory. The engines operate near the melting temperature of volcanic ash.

“Ingestion of ash can clog fuel nozzles, combustor, and turbine parts causing surging, flame out, immediate loss of engine thrust, and engine failure,” according to the observatory.

IF THE VOLCANOES ARE IN REMOTE LOCATIONS, HOW DANGEROUS CAN THEY BE?

Using information provided by the Federal Aviation Administration, the observatory estimates that more than 80,000 large aircraft per year, and 30,000 people per day, fly on routes downwind of Aleutian volcanoes, which are along great-circle routes between Europe, North America and Asia.

Airlines get excited when an ash cloud rises above 20,000 feet.

The jet stream can carry ash for hundreds of miles. Ash from Kasatochi Volcano in August 2008 blew all the way to Montana.

Redoubt volcano blew on Dec. 15, 1989, and sent ash 150 miles away into the path of a KLM jet carrying 231 passengers. Its four engines flamed out.

As the crew tried to restart the engines, “smoke” and a strong odor of sulfur filled the cockpit and cabin, according to a USGS account. The jet dropped more than 2 miles, from 27,900 feet to 13,300 feet, before the crew was able to restart all engines and land the plane safely at Anchorage.

WHAT ARE THE CHANCES FOR A MAJOR, CATASTROPHIC ERUPTION?

“That’s always a possibility but big eruptions have precursor signals,” said USGS research geophysicist Chris Waythomas, “That just doesn’t happen in 20 minutes.”

Months of below-ground unrest can precede a major eruption. The Alaska Volcano Observatory, Waythomas said, likely would be tipped off by movement of the huge volume of magma involved.

“It has to break a lot of rock to get to the surface,” he said.

Note: The above post is reprinted from materials provided by The Associated Press.

World’s Largest Meteorite

Hoba Meteorite near Grootfontein, Namibia

Name: Hoba “This is an OFFICIAL meteorite name”
Abbreviation: There is no official abbreviation for this meteorite.
Observed fall: No
Year found: 1920
Country: Namibia
Mass: 60 tons

The Hoba or Hoba West meteorite lies on the farm “Hoba West”, not far from Grootfontein, in the Otjozondjupa Region of Namibia. It has been uncovered but, because of its large mass, has never been moved from where it fell. The main mass is estimated at more than 60 tons, making it the largest known meteorite (as a single piece) and the most massive naturally occurring piece of iron known on Earth’s surface.

Impact

The Hoba meteorite impact is thought to have occurred more recently than 80,000 years ago. It is inferred that the Earth’s atmosphere slowed the object to the point that it impacted the surface at terminal velocity, thereby remaining intact and causing little excavation.

Assuming a drag coefficient of about 1.3, the meteor would have been slowed to about 720 miles per hour (0.32 km/s) from its speed on entering the Earth’s atmosphere, typically in excess of 10 km/s for similar objects. The meteorite is unusual in that it is flat on both major surfaces, possibly causing it to have skipped across the top of the atmosphere like a flat stone skipping on water.

Discovery

The Hoba meteorite left no preserved crater and its discovery was a chance event. The owner of the land, Jacobus Hermanus Brits, encountered the object while ploughing one of his fields with an ox. During this task, he heard a loud metallic scratching sound and the plough came to an abrupt halt. The obstruction was excavated, identified as a meteorite and described by Mr. Brits, whose report was published in 1920 and can be viewed at the Grootfontein Museum in Namibia.

Friedrich Wilhelm Kegel took the first published photograph of the Hoba meteorite.

Description and composition

Hoba is a tabloid body of metal, measuring 2.7×2.7×0.9 metres (8.9×8.9×3.0 ft). In 1920 its mass was estimated at 66 tons. Erosion, scientific sampling and vandalism reduced its bulk over the years. The remaining mass is estimated at just over 60 tons.

The meteorite is composed of about 84% iron and 16% nickel, with traces of cobalt. It is classified as an ataxite iron meteorite belonging to the nickel-rich chemical class IVB. A crust of iron hydroxides is locally present on the surface, owing to weathering.

Note: The above post is reprinted from materials provided by Wikipedia.

Five things you might not know about crystallography

1. 2014 – was the UNESCO Year of Crystallography.

The father and son combination of father William Henry Bragg and son William Lawrence Bragg first revealed the structure of salt and won the Nobel Prize in Physics in 1915 for their services ‘in the analysis of crystal structure by means of X-ray’. To date, the Braggs are the only father and son team to receive a Nobel Prize. In fact, Crystallography is the science or discipline directly attributable to winning the most Nobel Prizes, taking the award 28 times.

2. Around 90 per cent of all drugs are actually crystals.

That’s because it’s much easier to control the solid state of a crystalline structure – even if you’re using a gel, that would involve crystals that are suspended in a gooey substance to aid the delivery of the drug involved. Some drugs that are injected would also be comprised of small crystals as crystalline materials can be arranged in different ways, under different conditions, to create the required effect.

If you take a tablet, it has to dissolve in your gut and get across the gut wall into the bloodstream. How the crystals in the drugs are composed will define how readily they will dissolve in your gut. If you get the wrong form, the drug might go all the way through the body, or dissolve in the wrong place and be useless.

3. Did you know that quite a lot of the human body is made of crystals?

For example, most of the rods and cones in your eye that conduct the light or form an image are made of crystals. Around 65 per cent of the bone mass of an adult is made of hydroxyapatite crystal.

4. Another thing to consider, especially during the seasonal period, is that chocolate is crystalline.

The National X-ray Crystallography Service at Southampton has done a number of experiments on the crystalline structures of chocolate. The cocoa butter added controls the crystallinity and that is important because there are six different crystalline forms of chocolate. Perhaps surprisingly, the one that most chocolate wants to be – the most stable form – is the nasty one with the white coating on the top that nobody likes the taste of, but that’s what chocolate ultimately wants to be.

If you play around with the amount of cocoa butter, that affects the crystalline nature of the chocolate and that’s how you get different forms, tastes and textures and, hopefully, will direct you to the form of chocolate that everybody knows and loves.

5. Many people will be enjoying fireworks over the holiday period, but did you know that explosives are all crystals?

Here in Southampton, we have developed a new class of solid compound that means that you would no longer need to mix powders to create fireworks, much as the Chinese were doing centuries ago. The problem with explosive powders, or other substances like nitro-glycerine, is their volatility. However, if they were to be created in a more stable solid state, they would be safer to transport and easier to control.

One answer we have discovered is to move towards a different kind of high-energy material by growing crystals with firework-type properties in a scaffold or lattice-like structure, which stays stable and features channels and voids where you can put things like different dyes to create different colours. You could even put nitro-glycerine within such a structure and it would stay stable for as long as you like.

The applications for this kind of firework are not just for entertainment or defence. The airbags in our cars are also initiated by energetic materials that are all mini fireworks, so there are many civilian applications for these crystals as well.

Note: The above post is reprinted from materials provided by University of Southampton.

Diamonds could one day replace GPS

Diamond

Lab-grown red diamonds with an atomic defect could one day replace GPS systems thanks to their remarkable sensitivity to magnetic waves, scientists have suggested.

A team at Element Six, a tech company based in Oxfordshire, are exploring the remarkable properties of crystals with a so-called ‘nitrogen vacancy defect’ – a gap in the atomic lattice at the heart of the diamond.

These diamonds have demonstrated incredible sensitivity to magnetic waves at room temperature, and are currently able to detect the passing of a car 300 metres away.

The hope is that they could one day be attuned to pinpoint their own location on the surface of the planet by reading magnetic waves from the sun. This would eliminate the need for GPS satellites, which send signals back to earth to tell cars where they are.

Such a breakthrough could make driverless cars a reality, as it would allow autonomous vehicles to move safely around each other.

“If you have a device that is capable of sensing the surrounding magnetic fields, it also knows where it is,” explained principal research scientist Richard Bodkin. “So once you can harness all of those technologies into a single device, there is no reason why driverless cars can’t be realised.”

However such a development could be decades away, the scientists warned. Their work is focused on improving the magnetic sensitivity of synthetic diamonds, which could also be used to replace MRI sensors. This could result in a helmet or handheld scanner that would probe a patient’s body without putting them inside an MRI tube.

Element Six primarily focuses on developing diamond-edged cutting tools for use in heavy industry, such as drill bits for oil and gas companies. It is majority owned by diamond mining giant De Beers.

The company is also looking at how to use synthetic diamonds in quantum computing, a highly theoretical field that promises computational power far in excess of today’s digital machines.

Note: The above post is reprinted from materials provided by Telegraph.

Evidence for a new kind of water molecule, trapped inside an emerald

The image shows the “H12/6O” molecule trapped at low temperature within the emerald crystalline structure as revealed by neutron scattering. A macroscopic emerald crystal is also shown. Credit: ORNL/Jeff Scovil

The interactions of water with the surrounding rock ore deposits create geothermal energy and mineral deposits. The properties of water and other fluids change when they are confined in very small pores. In analyzing the properties of water molecules confined inside an emerald at extremely low temperature (about 5 K or -451 Fahrenheit), scientists at Oak Ridge National Laboratory found that individual molecules undergo a transition, essentially existing simultaneously as six copies of itself, each of which is, in a sense, 1/6 “present.” The formula might be written “H12/6O” instead of “H2O.” This is a completely new kind of water molecule, created through the agency of quantum tunneling, whose shape has been altered to conform to the symmetry of the environment in which it is trapped.

The Impact

The revelation of this tunneling state of water will enable scientists to better describe the thermodynamic properties and behavior of water in highly confined environments. Knowledge of the temperature dependence of the scattering signal serves as an important constraint on theoretical calculations of the H2O-H12/6O transition at very low temperature. Knowledge of the details of this transformation can then be used to make more accurate predictions of water diffusion and transport in higher temperature systems such as in the channels of cell membranes, in carbon nanotubes, and along grain boundaries and at mineral interfaces in a variety of geological environments.

Summary

The interactions of water with the surrounding rock matrix are responsible for geothermal energy, the formation of many ore deposits, and a number of other important geological processes. In many such systems, water may be present as no more than an ultrathin film along the boundaries between the mineral grains making up the rock.

Highly confined water is also present inside nanometer-sized channels present in the crystalline structures of some types of minerals and gems, where the atomic environment is much more regular and easier to characterize than in complex grain boundaries. New research by scientists at the Oak Ridge National Laboratory (ORNL) and their colleagues describes a new kind of water molecule, created by quantum tunneling, confined in hexagonal channels — 5 angstroms across — of the mineral beryl.

The discovery, made possible with experiments at ORNL’s Spallation Neutron Source and the Rutherford Appleton Laboratory in the United Kingdom, demonstrates that at low temperatures, water in these channels is “delocalized” over six symmetrically equivalent positions in the channel and assumes an unusual double-top-like shape (see the figure). This research not only provides the first evidence of a new quantum tunneling state of the water molecule, it also suggests that the vibrational spectra of surrounding minerals can reduce the activation energy for water transport on grain boundaries in geologic environments.

Compared to the non-tunneling molecule, the center of mass and the dipole moment of the delocalized water molecule are modified, thus modifying the interactions of the molecule with its surroundings and impacting our understanding of water and energy transport and reactivity. Neutron scattering and computational modeling revealed unique and unexpected behavior of water molecules under extreme confinement that is unmatched by any known gas, liquid, or solid states.

Reference:
A.I. Kolesnikov, G.F. Reiter, N. Choudhury, T.R. Prisk, E. Mamontov, A. Podlesnyak, G. Ehlers, A.G. Seel, D.J. Wesolowski, and L.M. Anovitz, “Quantum tunneling of water in beryl: A new state of the water moleculeExternal link.” Physical Review Letters 116, 167802 (2016). DOI: 10.1103/PhysRevLett.116.167802

Note: The above post is reprinted from materials provided by Department of Energy, Office of Science.

South American fossil tomatillos show nightshades evolved earlier than thought

The new fossil groundcherry Physalis infinemundi from Laguna del Hunco in Patagonia, Argentina, 52 million years old. This specimen displays the characteristic papery, lobed husk and details of the venation. Credit: Ignacio Escapa, Museo Paleontológico Egidio Feruglio

Delicate fossil remains of tomatillos found in Patagonia, Argentina, show that this branch of the economically important family that also includes potatoes, peppers, tobacco, petunias and tomatoes existed 52 million years ago, long before the dates previously ascribed to these species, according to an international team of scientists.

Tomatillos, ground cherries and husk tomatoes — members of the physalis genus — are unusual because they have papery, lantern-like husks, known to botanists as inflated calyces that grow after fertilization to extend around their fleshy, often edible berries. They are a small portion of the nightshade family, which includes many commercially, scientifically and culturally valuable plants among its more than 2,400 living species. This entire family has had a notably poor fossil record, limited to tiny seeds and wood with little diagnostic value that drastically limited understanding of when and where it evolved.

The researchers examined two fossil lantern fruit collected at Laguna del Hunco, Chubut, Patagonia, Argentina, in an area that was temperate rainforest when the plants grew, 52 million years ago. These are the only physalis fossils found among more than 6,000 fossils collected from this remote area, and they preserve very delicate features such as the papery husk and the berry itself. The fossil site, which has been the focus of a Penn State, Museo Palentologico Egidio Feruglio, Trelew, Argentina, and Cornell University project for more than a decade, was part of terminal Gondwana, comprised of the adjacent landmasses of South America, Antarctica and Australia during a warm period of Earth history, just before their final separation.

“These astonishing, extremely rare specimens of physalis fruits are the only two fossils known of the entire nightshade family that preserve enough information to be assigned to a genus within the family,” said Peter Wilf, professor of geosciences, Penn State. “We exhaustively analyzed every detail of these fossils in comparison with all potential living relatives and there is no question that they represent the world’s first physalis fossils and the first fossil fruits of the nightshade family. Physalis sits near the tips of the nightshade family’s evolutionary tree, meaning that the nightshades as a whole, contrary to what was thought, are far older than 52 million years.”

Typically, researchers look for fossilized fruits or flowers as their first choice in identifying ancient plants. Because the fruits of the nightshade family are very delicate and largely come from herbaceous plants with low biomass, they have little potential to fossilize. The leaves and flowers are also unknown from the fossil record. This presents a problem for understanding when and where the group evolved and limits the use of fossils to calibrate molecular divergence dating of these plants.

Molecular dating of family trees relies on actual dates of fossils in the family to work from. Because the previous dated fossils had little diagnostic value beyond their membership in the large nightshade family, molecular dating was difficult.

The researchers note in Science that “The fossils are significantly older than corresponding molecular divergence dates and demonstrate an ancient history for the inflated calyx syndrome.”

Molecular dates calibrated with previous fossils had placed the entire nightshade family at 35 to 51 million year ago and the tomatillo group, to which the 52 million year old fossils belong, at only 9 to 11 million years ago.

Using direct geologic dating of materials found with the fossils — argon-argon dating of volcanic tuffs and recognition of two magnetic reversals of the Earth’s poles — the team had previously dated the rocks containing the fossil fruit to 52 million years ago.

“Paleobotanical discoveries in Patagonia are probably destined to revolutionize some traditional views on the origin and evolution of the plant kingdom,” said N. Rubén Cúneo, CONICET, Museo Palentológico Egidio Feruglio. “In this regard, the Penn State/ MEF/Cornell scientific partnership is showing the strength of international collaborations to bring light and new challenges to the exciting world of discovering the secrets of Earth life.”

Mónica Carvalho, former Penn State M.S. student now a Ph.D. student at the School of Integrative Plant Science, Cornell, and Wilf did the evolutionary analysis of the morphology of current members of the family and the fossils, combined with genetic analysis of the living species.

“These fossils are one of a kind, since the delicate papery covers of lantern fruits are rarely preserved as fossils,” Carvalho said. “Our fossils show that the evolutionary history of this plant family is much older than previously considered, particularly in South America, and they unveil important implications for understanding the diversification of the family.”

All members of the physalis genus are New World species inhabiting South, Central and North America. Their center of diversity is Mexico.

The researchers note that the physalis fossils show a rare link from late-Gondwanan Patagonian to living New World plants, but most other fossil plants, such as eucalyptus, found at the site have living relatives concentrated in Australasia. That pattern reflects the ancient overland connection across terminal Gondwana from South America to Australia through Antarctica. The new research raises the possibility that more, potentially much older, nightshade fossils may be found at far southern locations.

“Our results reinforce the emerging pattern wherein numerous fossil plant taxa from Gondwanan Patagonia and Antarctica are substantially older than their corresponding molecular dates, demonstrating Gondwanan history to groups conjectured to have post-Gondwanan origins under entirely different paleogeographic and paleoclimatic scenarios,” the researchers wrote.

Reference:
Peter Wilf, Mónica R. Carvalho, María A. Gandolfo, N. Rubén Cúneo. Eocene lantern fruits from Gondwanan Patagonia and the early origins of Solanaceae. Science, 2017; 355 (6320): 71 DOI: 10.1126/science.aag2737

Note: The above post is reprinted from materials provided by Penn State.

Climate change could trigger strong sea level rise

Iceberg in the southeastern Weddell Sea region. Credit: Photo: Dr. Michael Weber

About 15,000 years ago, the ocean around Antarctica has seen an abrupt sea level rise of several meters. It could happen again. An international team of scientists with the participation of the University of Bonn is now reporting its findings in the magazine Scientific Reports.

University of Bonn’s climate researcher Michael E. Weber is a member of the study group. He says, “The changes that are currently taking place in a disturbing manner resemble those 14,700 years ago.” At that time, changes in atmospheric-oceanic circulation led to a stratification in the ocean with a cold layer at the surface and a warm layer below. Under such conditions, ice sheets melt more strongly than when the surrounding ocean is thoroughly mixed. This is exactly what is presently happening around the Antarctic.

The main author of the study, the Australian climate researcher Chris Fogwill from the Climate Change Research Center in Sydney, explains the process as follows: “The reason for the layering is that global warming in parts of Antarctica is causing land based ice to melt, adding massive amounts of freshwater to the ocean surface. At the same time as the surface is cooling, the deeper ocean is warming, which has already accelerated the decline of glaciers in the Amundsen Sea Embayment.” It appears global warming is replicating conditions that, in the past, triggered significant shifts in the stability of the Antarctic ice sheet.

To investigate the climate changes of the past, the scientists are studying drill cores from the eternal ice. Layer by layer, this frozen “climate archive” reveals its secrets to the experts. In previous studies, the scientists had found evidence of eight massive melting events in deep sea sediments around the Antarctic, which occurred at the transition from the last ice age to the present warm period. Co-author Dr. Weber from the Steinmann Institute of the University of Bonn says: “The largest melt occurred 14,700 years ago. During this time the Antarctic contributed to a sea level rise of at least three meters within a few centuries.”

The present discovery is the first direct evidence from the Antarctic continent which confirms the assumed models. The research team used isotopic analyzes of ice cores from the Weddell Sea region, which now flows into the ocean about a quarter of the Antarctic melt.

Through a combination with ice sheet and climate modeling, the isotopic data show that the waters around the Antarctic were heavily layered at the time of the melting events, so that the ice sheets melted at a faster rate. “The big question is whether the ice sheet will react to these changing ocean conditions as rapidly as it did 14,700 years ago,” says co-author Nick Golledge from the Antarctic Research Center in Wellington, New Zealand.

Reference:
C. J. Fogwill, C. S. M. Turney, N. R. Golledge, D. M. Etheridge, M. Rubino, D. P. Thornton, A. Baker, J. Woodward, K. Winter, T. D. van Ommen, A. D. Moy, M. A. J. Curran, S. M. Davies, M. E. Weber, M. I. Bird, N. C. Munksgaard, L. Menviel, C. M. Rootes, B. Ellis, H. Millman, J. Vohra, A. Rivera, A. Cooper. Antarctic ice sheet discharge driven by atmosphere-ocean feedbacks at the Last Glacial Termination. Scientific Reports, 2017; 7: 39979 DOI: 10.1038/srep39979

Note: The above post is reprinted from materials provided by University of Bonn.

Research sheds new light on high-altitude settlement in Tibet

A handprint image taken in 2006. Credit: Mark Aldenderfer

Humans likely established permanent settlements on the high-altitude Tibetan Plateau between 13,000-7,400 years ago, according to new research published this week in the journal Science.

That conclusion challenges the previously held view that permanent human occupation of the Tibetan Plateau began no earlier than 5,200 years ago, after the advent of agriculture. The new finding is, however, consistent with research on the genetics of modern Tibetan Plateau people showing that they adapted genetically to the high-elevation environment beginning at least 8,000 years ago.

The research team includes Randy Haas, a postdoctoral research associate in the University of Wyoming’s Department of Anthropology. The group was led by Michael Meyer of the University of Innsbruck in Austria and Mark Aldenderfer of the University of California-Merced. The multinational team includes scholars from institutions in Austria, Germany, New Zealand and the United States.

The researchers conducted an extensive analysis of human handprints and footprints found in 1998 in fossilized hot spring mud near the village of Chusang on Tibet’s central plateau, at an elevation of 14,000 feet above sea level. Early analysis of the archaeological site indicated that the prints were made by people about 20,000 years ago, but the more thorough analysis dates them to at least 7,400 years ago, and possibly as early as 13,000 years ago. That still makes the Chusang site the oldest reliably dated archaeological site on the Tibetan Plateau.

While some have suggested that a human presence on the Tibetan Plateau at those early dates was only a result of short-term, seasonal movement from low-elevation base camps, the new research shows that it is much more likely that the handprints and footprints were made by permanent residents. Haas shows that the distance between lowland environments and the Chusang site would have required at least 230 miles of foot travel across the Himalayan arc—a path far too long and treacherous for temporary use of the site, and far greater than what has been documented among most historic hunter-gatherers.

The early Tibetan Plateau settlers managed to survive at high elevation at least 7,400 years ago, before the development of an agricultural economy between 5,200-3,600 years ago.

“Although an agropastoral lifeway may have enabled substantial population growth after 5,000 years, it by no means was required for the early, likely permanent, occupation of the high central valleys of the Tibetan Plateau,” the researchers wrote.

Haas says the research sheds new light on human colonization of high-elevation environments. For example, researchers have been puzzled by the striking differences in how Tibetans and Andean highlanders adapted physiologically to the rigors of life at high elevations.

“High-elevation environments (over 8,000 feet above sea level) were some of the last places in the world that humans colonized, and so they offer something of a natural laboratory for studying human adaptation,” Haas says. “Research on high-elevation populations around the world tells us that there were multiple adaptive pathways involving various combinations of physiological, genetic and cultural responses. Our findings clarify that genetic and cultural responses on the Tibetan Plateau played out over considerably longer time spans than previously thought.”

Reference:
“Permanent human occupation of the central Tibetan Plateau in the early Holocene,” Science, DOI: 10.1126/science.aag0357

Note: The above post is reprinted from materials provided by University of Wyoming.

Where’s the center of North America? Geographer’s new method finds a new answer

Representative Image: North America

Where is the geographic center of a state, country or a continent?

It’s a question fraught with uncertainty. Do you include water in your calculation? What about islands? What happens when the shoreline shifts?

The U.S. Geological Survey alluded to these complexities in a 1964 report on the centers of states, which opened by stating, “There is no generally accepted definition of geographic center, and no completely satisfactory method for determining it.” More recently, various representatives of the agency have given quotes to newspapers saying much the same, hedging.

But to University at Buffalo geologist Peter Rogerson, PhD, the challenge of finding a middle doesn’t mean you shouldn’t try.

“There are all these people out there saying, ‘There’s no real good way to do this,'” says Rogerson, a SUNY Distinguished Professor of geography in UB’s College of Arts and Sciences. He respectfully disagrees: “As a geographer, my feeling is that if we want to come up with a good way of defining a center, we can and we should.”

In a 2015 paper in The Professional Geographer, an academic journal, Rogerson describes a new method for pinpointing the heart of a spatial entity. The approach improves on past techniques, he says, by taking the curvature of the Earth into account appropriately and by identifying geographic centers using a definition that’s mathematically sound.

In late 2016, he employed his method to find the heart of North America. The result was serendipitous: According to his calculations, the center of the continent is in a place called Center, a town of 570 people in North Dakota.

An odd fascination with geographic centers

In his 2015 study, Rogerson recounts Americans’ enduring interest in geographic centers, whether practical or not.

He writes that in the early and mid-19th century, county seats in the U.S. were routinely chosen based on their proximity to the county’s center, a practice geared toward promoting accessibility. Today, some communities have erected plaques or other monuments attesting to their (sometimes questionable) status as the center of their states.

Recognition as a geographic center can generate tourist dollars and civic pride, as Rogerson writes in The Professional Geographer: “The associated attachments often run surprisingly deep — deep enough for communities to do (usually good-natured) battle with each other and for journalists to run feel-good, public interest stories on what lies at the core of their region.”

He’s not sure why the idea of a geographic center is so intriguing to so many. But like a region’s highest mountain or lowest point, the center is a landmark, however elusive, that seems to resonate.

“It’s quirky. I think some people are just really interested in facts and the details of things,” Rogerson says. “For some people, the obsession is sports statistics, and for some people, it’s places.”

Better than a cardboard cutout balanced on a point

One early method for finding geographic centers was balancing a cardboard cutout of a region atop a needle-like point, Rogerson says. Technology has come a long way since then, of course, and researchers have developed more precise techniques.

Rogerson says there is actually a solid, mathematical definition for what a geographic center is: It’s the spatial equivalent of the center of gravity in physics, and its location minimizes the sum of the squared distances to all other points in a region.

Recent approaches to identifying geographic centers have varied, but one factor that has skewed some results is basing analyses on maps that fail to account appropriately for the curvature of the Earth — a property that affects the true distance between two locations.

Rogerson’s technique uses what geographers call an azimuthal equidistant map projection, which preserves important qualities related to distance when a rounded 3-D portion of the Earth is projected as a flat, 2-D surface.

Using this projection, paired with a computer program and a known mathematical formula for finding the centroids of 2-D polygons, he is able to narrow down a geographic center that meets the mathematical definition of what a center should be.

For geographic centers of states, which Rogerson reported in his 2015 paper, his calculations included both land and interior waters (like lakes), as well as islands. For Center, North Dakota, his calculations used the main land mass of North America, and not outlying islands. (Past calculations have placed the middle of North America further to the northeast, near towns more than 100 miles away by car in North Dakota.)

Of course, Rogerson has a small criticism of his own work: The azimuthal projection he’s using assumes the Earth is a sphere, but really, the planet is slightly ellipsoidal. “It could always be more exact,” he says.

Reference:
Peter A. Rogerson. A New Method for Finding Geographic Centers, with Application to U.S. States. The Professional Geographer, 2015; 67 (4): 686 DOI: 10.1080/00330124.2015.1062707

Note: The above post is reprinted from materials provided by University at Buffalo. Original written by Charlotte Hsu.

280 million-year-old fossil reveals origins of chimaeroid fishes

This image shows a reconstruction of Dwykaselachus oosthuizeni, a type of symmoriid shark now known to be an early chimaera. Credit: Kristen Tietjen

High-definition CT scans of the fossilized skull of a 280 million-year-old fish reveal the origin of chimaeras, a group of cartilaginous fish related to sharks. Analysis of the brain case of Dwykaselachus oosthuizeni, a shark-like fossil from South Africa, shows telltale structures of the brain, major cranial nerves, nostrils and inner ear belonging to modern-day chimaeras.

This discovery, published early online in Nature on Jan. 4, allows scientists to firmly anchor chimaeroids — the last major surviving vertebrate group to be properly situated on the tree of life — in evolutionary history, and sheds light on the early development of these fish as they diverged from their deep, shared ancestry with sharks.

“Chimaeroids belong somewhere close to the sharks and rays, but there’s always been uncertainty when you search deeper in time for their evolutionary branching point,” said Michael Coates, PhD, professor of organismal biology and anatomy at the University of Chicago, who led the study.

“Chimaeras are unusual throughout the long span of their fossil record,” Coates said. “Because of this, it’s been difficult to understand how they got to be the way they are in the first place. This discovery sheds new light not only on the early evolution of shark-like fishes, but also on jawed vertebrates as a whole.”

Chimaeras include about 50 living species, known in various parts of the world as ratfish, rabbit fish, ghost sharks, St. Joseph sharks or elephant sharks. They represent one of four fundamental divisions of modern vertebrate biodiversity. With large eyes and tooth plates adapted for grinding prey, these deep-water dwelling fish are far from the bloodthirsty killer sharks of Hollywood.

For more than 100 years, they have fascinated biologists. “There are few of the marine animals that on account of structure and relationships to other forms living and extinct have as great interest for zoologists and palaeontologists as the Chimaeroids,” wrote Harvard naturalist Samuel Garman in 1904. More than a century later, the relationship between chimaeras, the earliest sharks, and other early jawed fishes in the fossil record continues to puzzle paleontologists.

Chimaeras — named for their similarities to a mythical creature described by Homer as “lion-fronted and snake behind, a goat in the middle” — are unusual. Their anatomy comprises features reminiscent of sharks, ray-finned fishes and tetrapods, and their form is shaped by hardened bits of cartilage rather than bone. Because they are found in deep water, they were long considered rare. But as scientists gained the technology to explore more of the ocean, they are now known to be widespread, but their numbers remain uncertain.

After a 2014 study detailing their extremely slow-evolving genomes was published in Nature, interest in chimaeras blossomed. Of all living vertebrates with jaws, chimaeras seemed to offer the best promise of finding an archive of information about conditions close to the last common ancestor of humans and a Great White.

Like sharks, also reliant on cartilage, chimaeras rarely fossilize. The few known early chimaera fossils closely resemble their living descendants. Until now, the chimaeroid evolutionary record consisted mostly of isolated specimens of their characteristic hyper-mineralized tooth plates.

The Dwykaselachus fossil resolves this issue. It was originally discovered by amateur paleontologist and farmer Roy Oosthuizen when he split open a nodule of rock on his farm in South Africa in the 1980s. An initial description named it based on material visible at the broken surface of the nodule. It was carefully archived in the South African Museum in Cape Town, where its splendor awaited technology able to unwrap its long-shrouded secrets.

In 2013, when the University of the Witwatersrand Evolutionary Studies Institute obtained a micro CT scanner, Dr. Robert Gess, a South African Centre of Excellence in Palaeosciences partner and co-author of this study, began scanning Devonian shark fossils while he was based at the Rhodes University Geology Department. Coates encouraged him to investigate Dwykaselachus.

At the surface, Dwykaselachus appeared to be a symmoriid shark, a bizarre group of 300+ million-year-old sharks, known for their unusual dorsal fin spines, some resembling boom-like prongs and others surreal ironing boards.

CT scans showed that the Dwykaselachus skull was remarkably intact, one of a very few that had not been crushed during fossilization. The scans also provide an unprecedented view of the interior of the brain case.

“When I saw it for the first time, I was stunned,” Coates said. “The specimen is remarkable.”

The images, one reviewer commented, are “almost dripping with data.”

They show a series of telltale anatomical structures that mark the specimen as an early chimaera, not a shark. The braincase preserves details about the brain shape, the paths of major cranial nerves and the anatomy of the inner ear. All of which indicate that Dwyka belongs to modern-day chimaeras. The scans reveal clues about how these fish began to diverge from their common ancestry with sharks.

A large extinction of vertebrates at the end of the Devonian period, about 360 million years ago, gave rise to an explosion of cartilaginous fishes. Instead of what became modern-day sharks, Coates said, revelations from this study indicate that “much of this new biodiversity was, instead, early chimaeras.”

“We can now say that the first radiation of cartilaginous fishes after the end Devonian extinction was chimaeras, in abundance.” Coates said. “It’s the inverse of what we’ve got today, where sharks are far more common.”

Reference:
Michael I. Coates, Robert W. Gess, John A. Finarelli, Katharine E. Criswell, Kristen Tietjen. A symmoriiform chondrichthyan braincase and the origin of chimaeroid fishes. Nature, 2017; DOI: 10.1038/nature20806

Note: The above post is reprinted from materials provided by University of Chicago Medical Center.

When the Arctic coast retreats, life in the shallow water areas drastically changes

This image shows an eroding coastline in arctic summer, with outgoing mudslide on Herschel Island, Canada. Credit: Alfred-Wegener-Institut/Jaroslav Obu

The thawing and erosion of Arctic permafrost coasts has dramatically increased in the past years and the sea is now consuming more than 20 metres of land per year at some locations. The earth masses removed in this process increasingly blur the shallow water areas and release nutrients and pollutants. Yet, the consequences of these processes on life in the coastal zone and on traditional fishing grounds are virtually unknown. Scientists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) urge to focus our attention on the ecological consequences of coastal erosion in the January issue of the journal Nature Climate Change. According to the scientists, an interdisciplinary research program is required, and must involve policy-makers as well as inhabitants of the Arctic coasts right from the onset.

The difference could hardly be greater. In the winter, when the Beaufort Sea is frozen around the Canadian permafrost island of Herschel Island (Qikiqtaruk), the sea water in the sample bottles of the AWI researcher Dr Michael Fritz looks crystal clear. In summer, however, when the ice floes are melted and the sun and waves start to wear the cliff away, the water sample of the Potsdam geoscientist contains a cloudy broth.

“Herschel Island loses up to 22 metres of coast each year. The thawed permafrost slides down into the sea in the form of mud slides and blurs the surrounding shallow water areas so much that the brownish-grey sediment plumes reach many kilometres into the sea,” reports the polar researcher.

His observations of Herschel Island can now be transferred to large parts of the Arctic. 34 percent of the coasts around the world are permafrost coasts. This means, especially in the Arctic, that its soil contains a large amount of frozen water, which keeps the sediments together like cement. If the permafrost thaws, the binding effect fails. The sediments as well as animal and plant remains, which are frozen in the permafrost, are suddenly released in the water and are washed away by the waves.

In this process, greenhouse gases such as carbon dioxide and methane are released and lead to even greater global warming. The eroded material also contains a lot of nutrients and pollutants such as nitrogen, phosphorus or mercury. These substances enter the sea, where they are further transported, degraded or accumulated and permanently alter the living conditions in the shallow water area. “We can until now only guess the implications for the food chain. To date, almost no research has been carried out on the link between the biogeochemistry of the coastal zone and increasing erosion and what consequences this has on ecosystems, on traditional fishing grounds, and thus also on the people of the Arctic,” says Michael Fritz.

For this reason, Michael Fritz, the Dutch permafrost expert Jorien Vonk and AWI researcher Hugues Lantuit call on the polar research community to systematically investigate the consequences of coastal erosion for the arctic shallow water areas in the current issue of the journal Nature Climate Change. “The processes in the arctic coastal zone play an outstanding role for four reasons. Firstly, the thawed organic material is decomposed by microorganisms, producing greenhouse gases. Secondly, released nutrients stimulate the growth of algae, which can lead to the formation of low-oxygen zones. Thirdly, the addition of organic carbon increases the acidification of the sea, and fourth, the sediments are deposited on the seabed or are transported to the open ocean. This has direct consequences for the biology of the sea,” the authors say.

The urgency of the topic also increases with the warming of the Arctic: “We believe that the erosion of the Arctic coasts will increase drastically as a result of rising temperatures, the shrinking of the protective sea ice cover, and the rising sea level,” says AWI permafrost expert and co-author Professor Hugues Lantuit. He adds that “during the ice-free season the waves can hit the coast higher and affect more land.” An erosion of that magnitude will without a doubt alter the food web in the coastal zone, and will affect those people who depend on fishing and who cultivate their traditional way of life along Arctic coasts.

The main reason why research on this topic has not been carried out so far is linked to logistics. Much of the arctic coastal and shallow water zones are not accessible either by car or plane, or by large icebreakers. There is also no arctic-wide station network at the coast that could be used by researchers to collect reliable data. “Politics and science must find common solutions here, for example within the framework of the EU research program Horizon 2020. In order to make concrete statements on the consequences of erosion, we need an interdisciplinary research program that includes policy-makers and the Arctic population from the beginning,” says Michael Fritz.

Reference:
Michael Fritz, Jorien E. Vonk, Hugues Lantuit. Collapsing Arctic coastlines. Nature Climate Change, 2017; 7 (1): 6 DOI: 10.1038/nclimate3188

Note: The above post is reprinted from materials provided by Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research.

New study finds evolution of brain and tooth size were not linked in humans

This is a 3-D reconstruction of a modern human cranium showing the teeth and endocranial cast. Credit: George Washington University

A new study from the George Washington University’s Center for the Advanced Study of Human Paleobiology (CASHP) found that whereas brain size evolved at different rates for different species, especially during the evolution of Homo, the genus that includes humans, chewing teeth tended to evolve at more similar rates. The finding suggests that our brains and teeth did not evolve in lock step and were likely influenced by different ecological and behavioral factors.

This research challenges the classically accepted view that reduction of tooth size in hominins is linked with having a larger brain. The reasoning is that larger brains allowed hominins to start making stone tools and that the use of these tools reduced the need to have such large chewing teeth. But recent studies by other authors found that hominins had larger brains before chewing teeth became smaller, and they made and used stone tools when brains were still quite small, which challenges this relationship.

The new study evaluates this issue by measuring and comparing the rates at which teeth and brains have evolved along the different branches of the human evolutionary tree.

“The findings of the study indicate that simple causal relationships between the evolution of brain size, tool use and tooth size are unlikely to hold true when considering the complex scenarios of hominin evolution and the extended time periods during which evolutionary change has occurred,” said Aida Gómez-Robles, lead author of the paper and a postdoctoral scientist at GW’s CASHP.

To conduct the research, Dr. Gómez-Robles and her colleagues analyzed eight different hominin species. The researchers identified fast-evolving species by comparing differences between groups with those obtained when simulating evolution at a constant rate across all lineages, and they found clear differences between tooth evolution and brain evolution. If the classical view proposing co-evolution between brains and teeth is correct, they expected to see a close correspondence between species evolving at a fast rate for both traits. The differences they observed indicate that diverse and unrelated factors influenced the evolution of teeth and brains.

“Once something becomes conventional wisdom, in no time at all it becomes dogma,” said Bernard Wood, university professor of human origins at GW and a co-author of the paper. “The co-evolution of brains and teeth was on a fast-track to dogma status, but we caught it in the nick of time.”

The research published Jan. 2 in the Proceedings of the National Academy of Sciences.

Reference:
Aida Gómez-Robles, Jeroen B. Smaers, Ralph L. Holloway, P. David Polly, and Bernard A. Wood. Brain enlargement and dental reduction were not linked in hominin evolution. PNAS, 2017 DOI: 10.1073/pnas.1608798114

Note: The above post is reprinted from materials provided by George Washington University.

Star Sapphire Gemstone

A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as “star rubies”. Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that causes the appearance of a six-rayed “star”-shaped pattern when viewed with a single overhead light source.

The inclusion is often the mineral rutile, a mineral composed primarily of titanium dioxide. The stones are cut en cabochon, typically with the center of the star near the top of the dome. Occasionally, twelve-rayed stars are found, typically because two different sets of inclusions are found within the same stone, such as a combination of fine needles of rutile with small platelets of hematite; the first results in a whitish star and the second results in a golden-colored star.

During crystallisation, the two types of inclusions become preferentially oriented in different directions within the crystal, thereby forming two six-rayed stars that are superimposed upon each other to form a twelve-rayed star. Misshapen stars or 12-rayed stars may also form as a result of twinning. The inclusions can alternatively produce a “cat’s eye” effect if the ‘face-up’ direction of the cabochon’s dome is oriented perpendicular to the crystal’s c-axis rather than parallel to it. If the dome is oriented in between these two directions, an ‘off-center’ star will be visible, offset away from the high point of the dome.

Where Are They Found?

The most important deposits of fine star sapphire today are found in Australia, Myanmar (Burma), Sri Lanka and Thailand. Other significant star sapphire sources include Brazil, Cambodia, China, Kenya, Madagascar, Malawi, Nigeria, Pakistan, Rwanda, Tanzania, United States (Montana), Vietnam and Zimbabwe.

They are found dominantly in Sri Lanka, but also fine blue star sapphires have come from Burma. Black star sapphires have been found in Cambodia and India. Speaking of Burma, rubies also come from this famous source and we have this variety of corundum in our inventory as well.

The Star of Adam is the largest blue star sapphire which weighs 1404.49 carats. The gem was mined in the city of Ratnapura, southern Sri Lanka. The Black Star of Queensland, the largest gem-quality star sapphire in the world, weighs 733 carats. The Star of India (mined in Sri Lanka) (weighing 563.4 carats) is thought to be the second-largest star sapphire (the largest blue), and is currently on display at the American Museum of Natural History in New York City. The 182-carat Star of Bombay, (mined in Sri Lanka), located in the National Museum of Natural History, in Washington, D.C., is another example of a large blue star sapphire. The value of a star sapphire depends not only on the weight of the stone, but also the body color, visibility, and intensity of the asterism.

Star Sapphire Gemological Properties

Chemical Formula Al2O3 Aluminum oxide
Crystal Structure (Trigonal) doubly pointy, barrel-shaped, hexagonal pyramids, tabloid-shaped
Color Blue in various tones, pink, yellow, green, lavender, gray, black
Hardness 9 on the Mohs scale
Refractive Index 1.762 to 1.778
Density 3.95 to 4.03
Cleavage None
Transparency Transparent, translucent, opaque
Double Refraction or Birefringence -0.008
Luster Vitreous, silky
Fluorescence Blue: none; colorless: orange-yellow, violet

 

Star Sapphire Varieties

Besides for the varieties of Sapphire listed below, Sapphire with color other than blue are prefixed with their color names. The main gemstone colors in addition to blue Sapphire include:

  • Yellow Sapphire (sometimes also called “Golden Sapphire” if intensely colored)
  • Pink Sapphire
  • White Sapphire (describes Sapphire that is colorless)
  • Green Sapphire
  • Purple Sapphire
  • Orange Sapphire
  • Black Sapphire

Star Sapphire Uses

Sapphire is one of the most popular gemstones, and is used extensively in Jewelry. Fine colored Sapphire with a deep blue color and excellent transparency can reach several thousand dollars a carat. The blue variety is most often used in jewelry, but the yellow, pink, and orange “fancies” have recently become very popular. Green and light blue Sapphires are also known, but are less commonly used in jewelry. Opaque Black Sapphire is also used a minor gemstone.

Sapphire is used in all forms of jewelry, including bracelets, necklaces, rings, and earrings. It is used both as centerpiece gemstone in pendants and rings, as well as a secondary stone to complement other gemstones such as Diamonds. Star Sapphires are polished as cabochons, and, if clear, are extremely valuable.

The rare orange-pink variety, known as Padparadschah, can be even more valuable than fine blue Sapphire. Blue Sapphire is sometimes carved into cameos or small figures, especially the less transparent material. Synthetic Sapphire is often used as a cheap substitute for the natural material.

Reference:
Wikipedia: Sapphire
Minerals: The Precious Gemstone Sapphire
The Natural Sapphire Company: Star Sapphires

Cat’s Eye Gemstones

Translucent yellowish chatoyant chrysoberyl is called cymophane or cat’s eye. Cymophane has its derivation also from the Greek words meaning ‘wave’ and ‘appearance’, in reference to the haziness that visually distorts what would normally be viewed as a well defined surface of a cabochon.

This effect may be combined with a cat eye effect. In this variety, microscopic tubelike cavities or needle-like inclusions of rutile occur in an orientation parallel to the c-axis, producing a chatoyant effect visible as a single ray of light passing across the crystal. This effect is best seen in gemstones cut in cabochon form perpendicular to the c-axis. The color in yellow chrysoberyl is due to Fe3+ impurities.

Although other minerals such as tourmaline, scapolite, corundum, spinel and quartz can form “cat’s eye” stones similar in appearance to cymophane, the jewelry industry designates these stones as “quartz cat’s eyes”, or “ruby cat’s eyes” and only chrysoberyl can be referred to as “cat’s eye” with no other designation.

Gems lacking the silky inclusions required to produce the cat’s eye effect are usually faceted. An alexandrite cat’s eye is a chrysoberyl cat’s eye that changes color. “Milk and honey” is a term commonly used to describe the color of the best cat’s eyes. The effect refers to the sharp milky ray of white light normally crossing the cabochon as a center line along its length and overlying the honey-colored background. The honey color is considered to be top-grade by many gemologists but the lemon yellow colors are also popular and attractive. Cat’s eye material is found as a small percentage of the overall chrysoberyl production wherever chrysoberyl is found.

Cat’s eye really became popular by the end of the 19th century when the Duke of Connaught gave a ring with a cat’s eye as an engagement token; this was sufficient to make the stone more popular and increase its value greatly. Until that time, cat’s eye had predominantly been present in gem and mineral collections. The increased demand in turn created an intensified search for it in Sri Lanka.

The most famous and valuable cat’s eye gemstone is chrysoberyl cat’s eye. In fact when the term cat’s eye is used alone in the gem trade, it always refers to chrysoberyl cat’s eye. All other types of cat’s eye gems require an additional varietal designation, such as cat’s eye apatite.

Note: The above post is reprinted from materials provided by Wikipedia.

What is Asterism?

Asterism or star stone, is a name applied to the phenomenon of gemstones exhibiting a luminous star-like shape when cut en cabochon (shaped and polished rather than faceted). The typical asteria is the star sapphire, generally a bluish-grey corundum, milky or opalescent, with a star of six rays.

In red corundum the stellate reflection is less common, and hence the star-ruby occasionally found with the star-sapphire in Sri Lanka is among the most valued of “fancy stones”. When the radiation is shown by yellow corundum, the stone is called star-topaz. Cymophane, the chatoyant chrysoberyl known as cat’s eye, may also be asteriated. In all these cases the asterism is due to the reflection of light from twin-lamellae or from fine tubular cavities or thin enclosures definitely arranged in the stone. The astrion of Pliny the Elder is believed to have been a moonstone, since it is described as a colourless stone from India having within it the appearance of a star shining with the light of the moon. Star-stones were formerly regarded with much superstition.

Description

An asterism is an optical phenomenon displayed by some rubies, sapphires, and other gems (i.e. star garnet, star diopside, star spinel, etc.) of an enhanced reflective area in the shape of a “star” on the surface of a cabochon cut from the stone. Star sapphires and rubies get their asterism from the titanium dioxide impurities (rutile) present in them.[1] The Star-effect or “asterism” is caused by the dense inclusions of tiny fibers of rutile (also known as “silk”). The stars are caused by the light reflecting from needle-like inclusions of rutile aligned perpendicular to the rays of the star. However, since rutile is always present in star gemstones, they are almost never completely transparent.

A distinction can be made between two types of asterism:

  • Epiasterism, such as that seen in sapphire and most other gems, is the result of a reflection of light on parallel arranged inclusions inside the gemstone.
  • Diasterism, such as that seen in rose quartz, is the result of light transmitted through the stone. In order to see this effect, the stone must be illuminated from behind.

Note: The above post is reprinted from materials provided by Wikipedia.

Hawaii Island’s Kamokuna Lava Delta Collapses into the Ocean

A large section of the 26-acre lava delta created at the Kamokuna ocean entry from the 61g lava flow has collapsed into the ocean. It occurred on New Year’s Eve, December 31, 2016 at 2:45 p.m.

The collapse created large waves that caused older parts of the sea cliff, including a designated Hawaii Volcanoes National Park viewing area, to erode and wash away.

No one was injured, park officials said. There were no hikers on the cooled, black lava or tour helicopters overhead at the time of the late afternoon collapse.

The County of Hawaii also closed the Kalapana access to Hawaii Volcanoes National Park.

New study estimates frequency of volcanic eruptions

Credit: University of Leeds

Holidaymakers concerned about fresh volcanic eruptions causing flight-disrupting ash clouds might be reassured by a study setting out the first reliable estimates of their frequency.

While the University of Leeds-led research suggests that ash clouds are more common over northern Europe than previously thought, it puts the average gap between them at about 44 years.

It also reveals that these types of ash clouds have about a 20 per cent chance of occurring in northern Europe in any one decade.

Lead author Dr Liz Watson, from the School of Geography at Leeds, said: “Reliable estimates of the frequency of volcanic ash events could help airlines, insurance companies and the travelling public mitigate the economic losses and disruption caused by ash clouds in the future.”

The work began soon after 2010’s explosive eruption of Icelandic volcano Eyjafjallajökull, which caused more than 10 million air passengers to be stranded and cost the European economy an estimated £4 billion.

A team of researchers, which included academics from the universities of St Andrews and South Florida, compared records of volcanic ash fallout (also known as tephra) during the last 1,000 years.

Focusing on northern Europe which is downwind of Iceland, one of the world’s most active volcanic regions, they examined samples taken from peatlands and lake beds in mainland northern Europe, Great Britain, Ireland and the Faroe Islands, alongside previously existing samples taken from other sites across northern Europe.

The samples – cores up to seven metres long – were taken from peat and lake sediment where geological records are particularly well preserved.

Using electron microscopy and chemical analysis, the team identified tiny shards of preserved volcanic ash, called cryptotephra – about the width of a human hair – which enabled them to pinpoint at what point volcanic ash clouds had spread across the continent.

For many of the occurrences, the researchers were also able to match sample data to historical records or to existing geological data which charted specific eruptions.

The work found evidence of 84 ash clouds during the last 7,000 years, most of which could be traced to eruptions from Icelandic volcanoes.

More incidences of volcanic ash are recorded over the past 1,000 years, because evidence is better preserved and historical records are more complete, leading the team to estimate an average recurrence of 44 years.

Co-author Dr Graeme Swindles is Associate Professor of Earth System Dynamics in the School of Earth and Environment at Leeds.

He said: “In 2010, when Eyjafjallajökull erupted, people were really shocked – it seemed to come completely out of the blue, but the eruption of Grímsvötn, the following year, was an extraordinary coincidence.

“Although it is possible that ash clouds can occur on an annual basis, the average return interval for the last 1,000 years is around 44 years.

“The last time volcanic ash clouds affected northern Europe before the recent event was in 1947, 69 years ago – but aviation was much less intense at that time and it simply didn’t have the same sort of impact.

“Our research shows that, over thousands of years, these sorts of incidents are not that rare – but people wondering how likely it is that the 2010 chaos will be repeated in the next few years can feel somewhat reassured.”

The researchers also looked at the intensity of the eruptions responsible for producing volcanic ash clouds.

They found that volcanic activity likely to produce ashfall in northern Europe would typically measure four or above on the internationally-recognised Volcanic Explosivity Index (VEI).

“Eruptions can’t always be indexed rapidly,” explained co-author Dr Ivan Savov, also of Leeds’ School of Earth and Environment.

“But in cases where that calculation can be made early on, it will give a good indication of the likelihood of volcanic ash causing a major problem.

“The 2010 eruption cost billions in terms of lost revenues and there was an effect on the global economy, so the work we’ve been able to do to quantify the risk will be of interest to insurance companies trying to make sense of the potential for future air traffic disruptions.”

Reference:
E.J. Watson et al. Estimating the frequency of volcanic ash clouds over northern Europe, Earth and Planetary Science Letters (2017). DOI: 10.1016/j.epsl.2016.11.054

Note: The above post is reprinted from materials provided by University of Leeds.

Terrestrial Mesozoic ninja turtles

An illustration of the now-extinct sea turtle Desmatochelys padillai.Credit: Jorge Blanco

Turtles are an incredible evolutionary success story, with about 350 extant species that inhabit all major oceans and landmasses and from tropical to temperate climates. The fossil record of turtles is incredibly rich, and documents the adaptation of various sub-lineages to a broad range of habitat preferences, including several marine radiations. They’re also ridiculously cute, although whether their evolutionary accomplishment is down to this remains to be studied.

A slew of recent research articles have revealed much about the deep time evolutionary patterns in turtles and their ancestors. These large-scale, non-dinosaury studies get a frustratingly disproportional amount of public/media attention due to a low snarl/gore factor. However, they are arguably more significant due to the increasing importance of understanding the interaction of animals with their environments with ongoing major climatic disruptions and ongoing extinction severity.

The latest turtle-infused delight comes from David Nicholson as part of his post-doctoral research at the Natural History Museum in London, UK. Building on his research on global and continental diversity and niche partitioning, David and colleagues investigated the latitudinal diversity patterns that turtles and their ancestors (Testudinata, but here just ‘turtles’ to keep things simple) exhibited during the Mesozoic period based on their fossil record.

Why is latitude important? Well, the ‘latitudinal biodiversity gradient’ describes the pattern of increasing biodiversity as you go from the poles towards the equator, and is generally considered to be one of the first-order controls on much of modern life. Extant turtles, terrapins, and tortoises (collectively Testudines) are most diverse at around 25°N, so different to this general observation, and a feature of their global distribution that can probably be explained by bursts of species diversification related to changes in climate. But was this always the case?

What David and colleagues found peering back in time is a quite similar overall pattern throughout the evolutionary history of testudinatans – the group that includes modern Testudines and a whole bizarre array of now extinct turtle-like ancestors. During the Jurassic, they were most diverse at 15-30°N, after accounting for the way in which the continents have shifted since then. For the majority of the Cretaceous period, they were most diverse at 30-45°N, but at the very end of the Cretaceous, just before the mass extinction, this changed and expanded to a 30-60°N latitudinal belt. This ‘last minute play’ from turtles just prior to the extinction can be explained largely by the North American fossil record, in which we see the increasingly northward expansion of other groups such as dinosaurs at this time. Such range migration is coincident with short-term continent-level temperature increases around this time, which would have enabled turtles to migrate northwards and increase their geographical ranges, similar to what we see in the fossil record of crocodiles and their ancestors.

As well as this, turtles were able to survive in much higher latitudes in the northern and southern hemispheres throughout the Mesozoic compared to their living counterparts. This is because throughout the Mesozoic, the Earth was what we call a ‘greenhouse’ world, with overall much warmer climates than today which means that reptiles would have been able to survive a much broader range of latitudes.

Interestingly, the fossil record also tells us of a dearth of turtle diversity in the southern continents (Gondwana), much like in many other vertebrate groups, throughout the Jurassic and Cretaceous. It seems rather than this being due to a failure of the fossil record (i.e., we just haven’t found that many fossils there due to sampling histories or lack of ‘proper’ rocks), this lack seems to be due to the absence of suitable habitats in Gondwana during this time, so turtles preferred to stay up North.

What this shows is that, firstly, latitudinal diversity gradients are not always stable and linear, and do change through time due to varying factors such as continental shifts, dispersal events and vicariance, or environmentally-mediated changes such as major climatic disruption (sound familiar?). However, for turtles, their modern latitudinal diversity distribution does seem to have a deep time origin, going back some 150-200 million years or so, which is pretty cool! Or hot. Or whatever.

This discovery also challenges the commonly held assumption that latitudinal diversity gradients are both static and widespread among all living groups. This is probably due to at least a partial failure to appreciate the patterns that the fossil record reveal to us among researchers who focus exclusively on extant taxa. Naughty naughty… not that we’re biased at all as palaeontologists.

Reference:
David B. Nicholson et al. Latitudinal diversity gradients in Mesozoic non-marine turtles, Royal Society Open Science (2016). DOI: 10.1098/rsos.160581

Note: The above post is reprinted from materials provided by Public Library of Science.

How long did it take to hatch a dinosaur egg? Study says 3-6 months

A photo of a hatchling Protoceratops andrewsi fossil from the Gobi Desert Ukhaa Tolgod, Mongolia. Credit: Gregory Erickson, FSU

A human typically gives birth after nine months. An ostrich hatchling emerges from its egg after 42 days. But how long did it take for a baby dinosaur to incubate?

Groundbreaking research led by a Florida State University professor establishes a timeline of anywhere from three to six months depending on the dinosaur.

In an article in the Proceedings of the National Academy of Sciences, FSU Professor of Biological Science Gregory Erickson and a team of researchers break down the complicated biology of these prehistoric creatures and explain how embryonic dental records solved the mystery of how long dinosaurs incubated their eggs.

“Some of the greatest riddles about dinosaurs pertain to their embryology—virtually nothing is known,” Erickson said. “Did their eggs incubate slowly like their reptilian cousins—crocodilians and lizards? Or rapidly like living dinosaurs—the birds?”

Scientists had long theorized that dinosaur incubation duration was similar to birds, whose eggs hatch in periods ranging from 11-85 days. Comparable-sized reptilian eggs typically take twice as long—weeks to many months.

Because the eggs of dinosaurs were so large—some were about 4 kilograms or the size of a volleyball—scientists believed they must have experienced rapid incubation with birds inheriting that characteristic from their dinosaur ancestors.

Erickson, FSU graduate student David Kay and colleagues from University of Calgary and the American Museum of Natural History decided to put these theories to the test.

To do that, they accessed some rare fossils—those of dinosaur embryos.

“Time within the egg is a crucial part of development, but this earliest growth stage is poorly known because dinosaur embryos are rare,” said co-author Darla Zelenitsky, assistant professor of geoscience at University of Calgary. “Embryos can potentially tell us how dinosaurs developed and grew very early on in life and if they are more similar to birds or reptiles in these respects.”

The two types of dinosaur embryos researchers examined were those from Protoceratops — a sheep-sized dinosaur found in the Mongolian Gobi Desert whose eggs were quite small (194 grams)—and Hypacrosaurus, an enormous duck-billed dinosaur found in Alberta, Canada with eggs weighing more than 4 kilograms.

Erickson and his team ran the embryonic jaws through a CT scanner to visualize the forming dentition. Then, they extracted several of the teeth to further examine them under sophisticated microscopes.

Researchers found what they were looking for on those microscope slides. Growth lines on the teeth showed researchers precisely how long the dinosaurs had been growing in the eggs.

“These are the lines that are laid down when any animal’s teeth develops,” Erickson said. “They’re kind of like tree rings, but they’re put down daily. We could literally count them to see how long each dinosaur had been developing.”

Their results showed nearly three months for the tiny Protoceratops embryos and six months for those from the giant Hypacrosaurus.

“Dinosaur embryos are some of the best fossils in the world,” said Mark Norell, Macaulay Curator for the American Museum of Natural History and a co-author on the study. “Here, we used spectacular fossils specimens collected by American Museum expeditions to the Gobi Desert, coupled them with new technology and new ideas, leading us to discover something truly novel about dinosaurs.”

The implications of long dinosaur incubation are considerable.

In addition to finding that dinosaur incubation was similar to primitive reptiles, the researchers could infer many aspects of dinosaurian biology from the results.

Prolonged incubation put eggs and their parents at risk from predators, starvation and other environmental risk factors. And theories that some dinosaurs nested in the more temperate lower latitude of Canada and then traveled to the Arctic during the summer now seem unlikely given the time frame for hatching and migration.

The biggest ramification from the study, however, relates to the extinction of dinosaurs. Given that these warm-blooded creatures required considerable resources to reach adult size, took more than a year to mature and had slow incubation times, they would have been at a distinct disadvantage compared to other animals that survived the extinction event.

“We suspect our findings have implications for understanding why dinosaurs went extinct at the end of the Cretaceous period, whereas amphibians, birds, mammals and other reptiles made it through and prospered,” Erickson said.

Note: The above post is reprinted from materials provided by Florida State University.

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