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Multiple Cosmic Impacts 790,000 Years Ago With Global Consequences

Multiple Cosmic Impacts 790,000 Years Ago With Global Consequences | Amazing Science | Scoop.it
Approximately 790,000 years ago there were multiple cosmic impacts on earth with global consequences. Geoscientists from Heidelberg University reached this conclusion after dating so-called tektites from various parts of the world. The research group under the direction of Prof. Dr. Mario Trieloff studied several of such rock glasses, which originated during impacts of asteroids or comets. The Heidelberg scientists employed a dating method based on naturally occurring isotopes that allowed them to date the tektites more accurately than ever. Their studies show that the samples from Asia, Australia, Canada and Central America are virtually identical in age, although in some cases their chemistry differs markedly. This points to separate impacts that must have occurred around the same time. The results of their research funded by the Klaus Tschira Foundation were published in the journal “Geochimica et Cosmochimica Acta”.

The research group at the Institute of Earth Sciences and the Klaus Tschira Laboratory for Cosmochemistry uses isotope measurements to determine the age of craters caused by the impact of extraterrestrial rocks. “That's how we know when, where and how often projectiles struck the earth, and how big they were,” says Mario Trieloff. There have long been signs that a major event of this type took place on earth about a million years ago, according to Prof. Trieloff. This is evidenced by tektites, so-called rock glasses that arise during impact, whereby terrestrial material melts, is hurled up to several hundred kilometres and then hardens into glass.

“We have known about such tektites for some time from the Australasian region,” explains Dr. Winfried Schwarz, the study's primary author. These rock glasses form a strewn field that stretches from Indochina to the southernmost tip of Australia. Smaller tektites, known as microtektites, were also discovered in deep-sea drill cores off the coast of Madagascar and in the Antarctic. The rock glasses had been strewn over 10,000 kilometres, with some of them even leaving the earth's atmosphere. Using the 40Ar-39Ar dating method, which analyses the decay of the naturally occurring 40K isotope, the Heidelberg researchers succeeded in dating these tektites more accurately than ever before.

“Our data analysis indicates that there must have been a cosmic impact about 793,000 years ago, give or take 8,000 years,” explains Winfried Schwarz. The Heidelberg scientists also studied samples from Canada and Central America. The Canadian rock glasses had the same chemical composition and age as the Australasian tektites and could have covered similar “flight routes” as objects found in southern Australia or the Antarctic. Other finds must first confirm whether the recovery sites are really where the tektites originally landed or whether they for example were carried there by people, according to Dr. Schwarz.

The rock glasses from Central America are also tektites – the first specimens were found at Mayan sites of worship. In the meantime, hundreds of other finds have been made in Central America. “These tektites are clearly different in their chemical composition, and their geographical distribution also shows that they come from separate impacts,” explains Dr. Schwarz. “Surprisingly our age estimates prove that they originated 777,000 years ago with a deviation of 16,000 years. Within the error margin, this matches the age of the Australasian tektites.”
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Rapid loss of phytoplankton in the Indian Ocean

Rapid loss of phytoplankton in the Indian Ocean | Amazing Science | Scoop.it

A rapid loss of phytoplankton threatens to turn the western Indian Ocean into an “ecological desert,” a new study warns. The research reveals that phytoplankton populations in the region fell an alarming 30 percent over the last 16 years.


A decline in ocean mixing due to warming surface waters is to blame for that phytoplankton plummet, researchers propose online January 19 in Geophysical Research Letters. The mixing of the ocean’s layers ferries phytoplankton nutrients from the ocean’s dark depths up into the sunlit layers that the mini plants inhabit.


The loss of these microbes, which form the foundation of the ocean food web, may undermine the region’s ecosystem, warns study coauthor Raghu Murtugudde, an oceanographer at the University of Maryland in College Park.


“If you reduce the bottom of the food chain, it’s going to cascade,” Murtugudde says. The phytoplankton decline may be partially responsible for a 50 to 90 percent decline in tuna catch rates over the last half-century in the Indian Ocean, he says. “This is a wake-up call to look if similar things are happening elsewhere.”


In the 20th century, surface temperatures in the Indian Ocean rose about 50 percent more than the global average. Previous investigations into this ocean warming’s impact on phytoplankton suggested that populations had increased. But those studies looked at only a few years of data — not long enough to clearly identify any long-term trend.


Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology in Pune, Murtugudde and colleagues tracked the microscopic phytoplankton from space. Phytoplankton, like land plants, are tinted green. When the sea surface is filled with phytoplankton, the water takes on a lighter, greener tinge. As the phytoplankton population thins, the water turns darker and bluer.

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The Ominous Greenhouse Gas Accumulation Continues: Peak Methane Approaches 3,000 Parts Per Billion

The Ominous Greenhouse Gas Accumulation Continues: Peak Methane Approaches 3,000 Parts Per Billion | Amazing Science | Scoop.it

The world finally appears like it’s slowly starting to wake up from the grips of a fossil fuel influence-induced fever dream. Slowly, despite endemic political meddling by these powerful entities, some changes are starting to happen. Global carbon emissions growth remained flat during 2014 and likely 2015. Renewable energy adoption ramped up. Some major international commitments to reducing global carbon emissions were made. But the very pertinent question must be asked — are we waking up fast enough? And the still rapidly growing concentrations of gasses that heat the Earth’s atmosphere would seem to supply the answer in the form of a resounding, thunderous — “NO!”


On January 8th of 2016, we saw another record methane reading for the global atmosphere. The most recent single point peak for NOAA’s METOP measure hit a new all-time atmospheric high of 2,963 parts per billion or just 37 parts per billion shy of the milestone 3,000 parts per billion threshold. Another record methane spike rockets its way toward the ominous 3,000 parts per billion milestone in the NOAA METOP satellite array. The location of the current spike appears to be in the region of the Arctic where a number of very large carbon stores are now starting to warm up. Image source: NOAA OSPO.


In the broader context, we continue to see rising average global methane concentrations after a pause in atmospheric increases during the 1990s through the mid 2000s. This rate of increase is a sign that either new human sources, new global feedbacks from methane sources, or a combination of the two are pushing global totals higher. It is worth noting that the lower Latitude measures like Mauna Loa, however, did not pick up a signal that some kind of major-to-catastrophic environmental methane emission was underway. A situation some observational scientists fear may be possible, but that other, more well-established specialists tend to consider far, far less likely. Regardless of the current scientific conjecture, heightened and rising methane readings in the Arctic remain rather troubling.

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Current pace of environmental change is unprecedented in Earth's history

Current pace of environmental change is unprecedented in Earth's history | Amazing Science | Scoop.it

University of Bristol Cabot Institute researchers and their colleagues today published research that further documents the unprecedented rate of environmental change occurring today.


The research, published online on 4 January in Nature Geosciences reconstructs the changes in atmospheric carbon dioxide (pCO2) during a global environmental change event that occurred about 120 Million years ago. New geochemical data provide evidence that pCO2 increased in response to volcanic outgassing and remained high for around 1.5-2 million years, until enhanced organic matter burial in an oxygen-poor ocean caused areturn to original levels.


Lead author Dr David Naafs explained: 'Past records of climate change must be well characterised if we want to understand how it affected or will affect ecosystems. It has been suggested that the event we studied is a suitable analogue to what is happening today due to human activity and that a rapid increase in pCO2 caused ocean acidification and a biological crisis amongst a group of calcifying marine algae. Our work confirms that there was a large increase in pCO2. The change, however, appears to have been far slower than that of today, taking place over hundreds of thousands of years, rather than the centuries over which human activity is increasing atmospheric carbon dioxide levels. So despite earlier claims, our research indicates that it is extremely unlikely that widespread surface ocean acidification occurred during this event.'


The observation that yet another putative 'rapid' geological event is occurring perhaps a thousand times slower than today and not associated with widespread surface ocean acidification has been the focus of much recent research at the University of Bristol. Co-author Professor Daniela Schmidt, who was also a Lead Author on the IPCC WGII report on Ocean systems, emphasised that today's finding builds on one of the IPCC's key conclusions: that the rate of environmental change occurring today is largely unprecedented in Earth history. She said, 'This is another example that the current rate of environmental change has few if any precedents in Earth history, and this has big implications for thinking about both past and future change.'


The research was possible due to the exceptional Spanish section that the team analysed. Co-author Professor José Manuel Castro of the University of Jaen adds, 'The sediments at Cau accumulated very rapidly resulting in an expanded section. This allowed the high resolution multidisciplinary analysis that are the basis for this important study.'


Senior Author and Director of the University's Cabot Institute, Professor Rich Pancost, added, 'We often use the geological record to help us test or expand our understanding of climate change, for example, determining the sensitivity of Earth's temperature to higher CO2 levels. But testing the risks associated with the pace of modern environmental change is proving problematic, due to a lack of similar rapid changes in the geological past. Consequently, these risks, in this case to the marine ecosystems on which so many of us depend, remain associated with profound uncertainty. Decreasing CO2 emissions, as recently agreed in Paris, will be necessary to avoid these risks.'

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Helium anomaly preceded Mount Ontake eruption

Helium anomaly preceded Mount Ontake eruption | Amazing Science | Scoop.it
University of Tokyo researchers discovered an increase in a helium isotope during a ten-year period before the 2014 Mount Ontake eruption in central Japan. The finding suggests that this helium isotope anomaly is related to activation of the volcano's magma system and could be a valuable marker for long-term risk mitigation concerning volcanic eruption.


Small quantities of the isotope helium-3 are present in the mantle, while helium-4 is produced in the crust and mantle by radioactive decay. A higher ratio of helium-3 to helium-4 therefore indicates that a sample of helium gas originates from the mantle rather than the crust. Previous research suggested that variation of helium isotopic ratios over time in crater fumaroles and hot springs correlates well with volcanic activity.


However, helium anomalies reported in these studies were all related to magmatic eruptions, and not to hydro-volcanic or phreatic eruptions, caused when a heat source such as magma vaporizes water to steam. Because phreatic eruptions are highly local phenomena, they are extremely difficult to predict. Mount Ontake, which erupted unexpectedly on September 27, 2014 just before noon, is believed to have been a phreatic eruption, and resulted in 58 deaths with 5 still missing.

An international research group lead by Professor Yuji Sano at the Atmosphere and Ocean Research Institute, the University of Tokyo, found that prior to the 2014 eruption, the helium-3 to helium-4 ratio at the hot spring closest to the volcanic cone increased significantly from June 2003 to November 2014, while that at distant hot springs showed no significant change. In addition, the helium isotopic ratios of the closest hot spring remained constant from November 1981 to June 2000.

These findings suggest that helium anomalies are also associated with phreatic eruptions. The research group suggests that increased input of magmatic gas over a ten-year period resulted in the slow pressurization of the volcanic conduit and eventually lead to the eruption.

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Scientists on a mission to drill a hole deep enough to reach the Earth's crust

Scientists on a mission to drill a hole deep enough to reach the Earth's crust | Amazing Science | Scoop.it

Scientists will set out this week to drill a hole into the Indian Ocean floor to try to get below the Earth's crust for the first time.


They want to sample rock from the planet's mantle - its deep interior. In the process, the researchers hope to check their assumptions about the materials from which the crust itself is made. It will probably take several years to drop the full 5 to 5.5km, says co-team leader, Prof Chris MacLeod. This is in addition to the 700m of water between the drilling ship, the Joides Resolution (JR), and the seabed.


"In total, we think it will take three expeditions," the Cardiff University geologist told BBC News. "The science is approved and we have funding for this initial two-month investigation. But we will need to come back and we may not complete the task until the 2020s."


There have been several attempts to drill into the mantle, but none has yet succeeded. This latest effort may fare better, however, because faulting and erosion have already thinned the crust at the targeted drill site, known as Atlantis Bank on the South West Indian Ridge of the Indian Ocean.


The project, which is running under the auspices of the International Ocean Discovery Program (IODP), would give scientists access ultimately to fresh, unaltered peridotite - the rock, rich in olivine minerals, that, because of the size of the mantle, makes up the bulk material of the planet's interior.

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Fresh Climate Data Confirms 2015 Is Unlike Any Other Year in Human History

Fresh Climate Data Confirms 2015 Is Unlike Any Other Year in Human History | Amazing Science | Scoop.it
Over the past few days, a bevy of climate data has come together to tell a familiar yet shocking story: Humans have profoundly altered the planet’s life-support system, with 2015 increasingly likely to be an exclamation point on recent trends.

On Monday, scientists at Britain’s national weather service, the Met Office, said our planet will finish this year more than one degree Celsius warmer than preindustrial levels for the first time. That figure is halfway to the line in the sand that scientists say represents “dangerous” climate change and global leaders have committed to avoid—an ominous milestone.

This year’s global heat wave—about two-tenths of a degree warmer than 2014, a massive leap when averaged over the entire planet—can be blamed most immediately on an exceptionally strong El Niño but wouldn’t exist without decades of heat-trapping emissions from fossil fuel burning. Separate data released on Monday by the U.S. National Oceanic and Atmospheric Administration showed the current El Niño, a periodic warming of the tropical Pacific Ocean, has now tied 1997 for the strongest event ever measured, at least on a weekly basis.

"We've had similar natural events in the past, yet this is the first time we are set to reach the 1 degree marker and it's clear that it is human influence driving our modern climate into uncharted territory," said Stephen Belcher, director of the Met Office’s Hadley Centre in a statement.
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NASA Study: Long Term Antarctic Ice Sheet Gains Still Outweigh Short Term Losses

NASA Study: Long Term Antarctic Ice Sheet Gains Still Outweigh Short Term Losses | Amazing Science | Scoop.it
A new NASA study says that an increase in Antarctic snow accumulation that began 10,000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers.

The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.

According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed   to 82 billion tons of ice per year between 2003 and 2008.

“We’re essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica,” said Jay Zwally, a glaciologist with NASA Goddard Space Flight Center in Greenbelt, Maryland, and lead author of the study, which was published on Oct. 30 in the Journal of Glaciology. “Our main disagreement is for East Antarctica and the interior of West Antarctica – there, we see an ice gain that exceeds the losses in the other areas.”  Zwally added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”

Scientists calculate how much the ice sheet is growing or shrinking from the changes in surface height that are measured by the satellite altimeters. In locations where the amount of new snowfall accumulating on an ice sheet is not equal to the ice flow downward and outward to the ocean, the surface height changes and the ice-sheet mass grows or shrinks.

But it might only take a few decades for Antarctica’s growth to reverse, according to Zwally. “If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they’ve been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years -- I don’t think there will be enough snowfall increase to offset these losses.”
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Physicists crack mystery of the spectacular hexagonal stones of the Giant's Causeway

Physicists crack mystery of the spectacular hexagonal stones of the Giant's Causeway | Amazing Science | Scoop.it

The formation of the spectacular hexagonal stone columns at Ireland's Giant's Causeway and similar structures around the world can be explained by two new models of how stone fractures. That is the claim of researchers in Germany who have created models to describe how the hexagonal columns emerge from an initial rectangular pattern of cracks in cooling lava. Beyond addressing a question that has intrigued geologists for centuries, the new models may also help in the study of cracking in other materials, such as cooling ceramics.


Located on the north coast of County Antrim, the Giant's Causeway is renowned for its hexagonal columns of basalt, formed from an extensive lava plateau that was erupted around 55 million years ago. While local legend says the spectacular feature was built by the giant Finn MacCool, geologists know that the interlocking columns are a result of the lava shrinking as it cools – with the surface of the solidifying rock contracting faster than the material beneath. This results in stresses, which are relieved by cracks that spread from the surface downwards.


Why hexagons emerge, however, is not well understood because the cracks first form a rectangular pattern. According to team memberMartin Hofmann of the Technische Universität Dresden, the rectangular pattern occurs because the maximum amount of energy is released from the cooling material when cracks develop at 90° to each other.


As the lava cools, however, the initially rectangular columns gradually transform into more hexagonal shapes, with the T-junctions of the fledgling fracture patterns evolving into Y-junctions over time. This is also seen in laboratory experiments with solidifying starch, which undergoes a similar transition in fracture patterns.


In their new study, Hofmann and colleagues explore how these fracture patterns evolve using two 3D models based on the theory of linear elastic fracture mechanics. This approach describes how crack patterns evolve in a uniform lava layer while ensuring that the optimum amount of energy is released in the process. This new approach, Hofmann says, "sets itself apart by its proximity to the mechanics of the actual process of this pattern shift". The first of the two models takes a purely analytical approach, whereas the second is based on a 3D finite-element numerical simulation.


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Ocean Floor Geology Revealed

Ocean Floor Geology Revealed | Amazing Science | Scoop.it

Scientists from the University of Sydney’s School of Geosciences, Australia, have led the creation of the world’s first digital map of the seafloor’s geology. The composition of the seafloor, covering 70 percent of the Earth’s surface, has been mapped after the most recent map was hand drawn in the 1970s. Published in Geology, the map will help scientists better understand how our oceans have responded, and will respond, to environmental change. It also reveals the deep ocean basins to be much more complex than previously thought.


The deep ocean floor is a graveyard with much of it made up of the remains of microscopic sea creatures called phytoplankton thriving in sunlit surface waters. The composition of these remains can help decipher how oceans have responded in the past to climate change. A special group of phytoplankton called diatoms produce about a quarter of the oxygen we breathe and make a bigger contribution to fighting global warming than most plants on land. Their dead remains sink to the bottom of the ocean, locking away their carbon.


The new seafloor geology map demonstrates that diatom accumulations on the seafloor are nearly entirely independent of diatom blooms in surface waters in the Southern Ocean. This disconnect demonstrates that the researchers, amongst them co-author  Professor Dietmar Muller from the University of Sydney, understand the carbon source, but not the sink. More research is needed to better understand this relationship.


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YEC Geo's curator insight, September 12, 2015 9:02 AM

The good news is that it's available for free digital download here:  http://portal.gplates.org/#SEAFLOOR

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The magnetic mystery at the center of the Earth

The magnetic mystery at the center of the Earth | Amazing Science | Scoop.it
The history of the planet’s all-important magnetic field has scientists ramping up simulations and lab experiments to resolve a baffling paradox.


Earth’s depths are a hellish place. More than 5,000 kilometers belowground, the iron-rich core scorches at temperatures comparable to the sun’s surface and crushes at pressures akin to the weight of 20 blue whales balanced on a postage stamp. This extreme environment helps generate Earth’s magnetic field, the planetwide force that makes life on the surface possible. When the sun occasionally belches a blast of electrically charged particles at Earth, the magnetic field redirects the incoming bombardment. Without this magnetic defense, solar storms would fry any unsuspecting life-forms on the surface and gradually strip away Earth’s atmosphere.


For decades, scientists debated and fine-tuned their understanding of Earth’s magnetism. Heat flowing through the liquid outer core helps slosh the molten iron, generating a magnetic field, the general consensus holds. In the last few years, however, new investigations of Earth’s magnetic bodyguard have thrown a wrench into any sense of common ground. In 2012, scientists proposed that iron in the planet’s core conducts heat more readily than previously thought. That would imply less mixing in the outer core and a young Earth with only a meager magnetic field, if any at all. Yet ancient rocks reveal magnetic records of an early, powerful magnetic field protecting the planet billions of years ago.


In January, supercomputer simulations offered a possible resolution to this paradox. Simulating how electrons ricochet around iron atoms at the extremes of temperature and pressure found in Earth’s core suggested that iron’s heat conductivity could actually be low enough to allow a strong magnetic field during Earth’s youth. For a few brief weeks, researchers thought the mystery might be solved. In recent months, however, actual experiments using diamonds and lasers to re-create the intense conditions of the planet’s core raise doubts that the paradox will be resolved so easily.


In 2013, Hirose and colleagues predicted such a trend in Physics of the Earth and Planetary Interiors, suggesting that iron eventually reaches a point where the average distance an electron travels before bumping into an atom is comparable to the distance between each iron atom. At this point, with fewer remaining obstacles to bump into, the resistance to the movement of electrons will plateau even as temperatures continue to rise, they argue.


“Well, then we’re back to the paradox for now, it seems,” Smirnov said after hearing about the Hirose group’s new findings. Even with such high thermal conductivity values, the new core paradox may still be solvable, Driscoll said in May at a meeting of the American Geophysical Union and other organizations. A large enough heat flow through Earth’s interior can generate convection even when conductivity is high, he says.


Extra heat could come from the decay of radioactive elements, he proposes. In April, researchers reported in Nature that the core could contain a significant amount of radio­active uranium and thorium. Driscoll calculates that even a relatively small amount of radioactivity in the modern core would translate into a sizable boost to the ancient magnetic field. If just a small amount of radioactivity warms the core today, that would mean that billions of years ago plenty of radioactive atoms would have been around to help fuel the heat flow, he explains. “There are other knobs you can turn to get yourself out of the problem,” Driscoll says.


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Tom Latulipe's curator insight, September 9, 2015 9:37 AM

Magnets are very cool and critical to modern life.  Amazing about how we still don't know everything about them.   

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Gold and silver found in abundance in underneath volcanoes

Gold and silver found in abundance in underneath volcanoes | Amazing Science | Scoop.it

Water located in deep reservoirs located in the Taupo Volcanic Zone in New Zealand is rich with gold and silver, geoscientists say. High grade deposits of precious and other types of metals are said to dissolve in magma-heated water, or hot springs, but technologies needed to extract them safely are yet to be developed.


Researchers have identified at least six deep reservoirs expected to yield high levels of gold and silver. According to a report published in the journal Geothermics this month, gold concentrations reached 20 parts per billion while silver concentrations hit 2,000 parts per billion.


Geoscientist and lead author Stuart Simmons from the University of Utah says technologies must be developed to help retrieve millions of dollars in gold and silver while also ensuring lasting production. He and his colleagues suggest a process that incorporates a two-phase pipeline.

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Scientists Explain Why Greenwich Prime Meridian Moved 102 Meters Since 1884

Scientists Explain Why Greenwich Prime Meridian Moved 102 Meters Since 1884 | Amazing Science | Scoop.it

The ‘Prime Meridian’ that’s been running through the Royal Observatory at Greenwich, UK, since 1884 is now located 335 feet (102 meters) east of its historic spot. Dr Ken Seidelmann from the University of Virginia and his colleagues investigated the cause of this apparent discrepancy.


In 1884, the International Meridian Conference recommended that Earth’s prime meridian “to be employed as a common zero of longitude and standard of time-reckoning throughout the globe” pass through the “center of the transit instrument at the Observatory of Greenwich.”


This instrument – named the Airy Transit Circle for its designer, British Astronomer Royal Sir George Biddell Airy – is a nineteenth-century telescopic device for measuring star positions, and could be used for determining local time. Today, tourists visiting its meridian line must walk east approximately 335 feet before their satellite-navigation receivers indicate zero longitude.


Why? Because newer technologies – primarily the superb accuracy of GPS, which uses satellites to precisely measure grid coordinates at any point on the Earth’s surface – replaced the traditional telescopic observations used to measure the Earth’s rotation.


“With the advancements in technology, the change in the prime meridian was inevitable. Perhaps a new marker should be installed in the Greenwich Park for the new prime meridian,” said Dr Seidelmann, who is a co-author of the paper published in the Journal of Geodesy.


Dr Seidelmann and co-authors concluded that a slight deflection in the natural direction of gravity at Greenwich is responsible for the offset, along with the maintenance of continuity of astronomical time. According to the team, the 335-foot offset can be attributed to the difference between two conventional methods of determining coordinates: astronomical versus geodetic, which refers to a set of reference points used to locate places on the Earth.


Their difference is known as ‘deflection of the vertical,’ and high-resolution global gravitational models confirm that the east-west component of this deflection is of the proper sign and magnitude at Greenwich to account for the entire shift. Because our planet is not perfectly round, and because different locations on Earth have different terrain features affecting gravitational pull, traditional ways to measure longitude have built-in variations, or errors, based on the specific location where measurements are taken.


The observations were based on a vertical determined from a basin of mercury and were dependent on local conditions.

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Colossal Antarctic ice-shelf collapse followed last ice age

Colossal Antarctic ice-shelf collapse followed last ice age | Amazing Science | Scoop.it
In a new study that provides clues about how Antarctica's nation-sized Ross Ice Shelf might respond to a warming climate, U.S. and Japanese oceanographers have shown that a 100,000-square-mile section of the ice shelf broke apart within 1,500 years during a warming period after the last ice age.

The Ross Ice Shelf is the world's largest ice shelf, a vast floating extension of the West Antarctic Ice Sheet that is about the size of France. But at the end of the last ice age, it extended much farther north and covered the entire Ross Sea.

A study in this week's Proceedings of the National Academy of Sciences details how the ice shelf shrank during a period of climate warming following the ice age. The paper was co-authored by Rice University oceanographer John Anderson, postdoctoral research associate Lauren Simkins, graduate student Lindsay Prothro and colleagues at the University of Tokyo.

"At the height of the last ice age, we know that the sheet of ice covering the Antarctic continent was larger and thicker than it is today," said Anderson, Rice's Maurice Ewing Professor of Oceanography and professor of Earth science. "This continent-enveloping ice sheet extended all the way to the continental shelf, and in western Antarctica it filled the entire Ross Sea basin."

While people typically think of continents as landmasses that rise above the sea, the margins of all continents, including Antarctica, extend well beyond their shores to include continental shelves, subsea aprons that are far more shallow than the deep ocean abysses that mark the continental boundary.

In western Antarctica, the Ross Sea is characterized by a continental shelf that extends nearly 1,000 miles from the coast and is as much as 3,500 feet deep. Anderson said the geologic record shows that as recently as 18,000 years ago the entire Ross basin was filled with ice that was so thick and heavy it was grounded on the seafloor all the way to the edge of the continental shelf.
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New analysis of trace element ratios suggests that plate tectonics began about 3 billion years ago

New analysis of trace element ratios suggests that plate tectonics began about 3 billion years ago | Amazing Science | Scoop.it

Earth has some special features that set it apart from its close cousins in the solar system, including large oceans of liquid water and a rich atmosphere with just the right ingredients to support life as we know it. Earth is also the only planet that has an active outer layer made of large tectonic plates that grind together and dip beneath each other, giving rise to mountains, volcanoes, earthquakes and large continents of land.

Geologists have long debated when these processes, collectively known as plate tectonics, first got underway. Some scientists propose that the process began as early as 4.5 billion years ago, shortly after Earth's formation. Others suggest a much more recent start within the last 800 million years. A study from the University of Maryland provides new geochemical evidence for a middle ground between these two extremes: An analysis of trace element ratios that correlate to magnesium content suggests that plate tectonics began about 3 billion years ago. The results appear in the January 22, 2016 issue of the journal Science.


"By linking crustal composition and plate tectonics, we have provided first-order geochemical evidence for the onset of plate tectonics, which is a fundamental Earth science question," said Ming Tang, a graduate student in geology at UMD and lead author of the study. "Because plate tectonics is necessary for the building of continents, this work also represents a further step in understanding when and how Earth's continents formed."

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We are entering the Anthropocene - hard evidence for a human-driven Earth

We are entering the Anthropocene - hard evidence for a human-driven Earth | Amazing Science | Scoop.it

The evidence for a new geological epoch which marks the impact of human activity on the Earth is now overwhelming according to a recent paper by an international group of geoscientists. The Anthropocene, which is argued to start in the mid-20th Century, is marked by the spread of materials such as aluminium, concrete, plastic, fly ash and fallout from nuclear testing across the planet, coincident with elevated greenhouse gas emissions and unprecedented trans-global species invasions.


An international group of scientists is studying whether human activity has driven the Earth into a new geological epoch - the Anthropocene. They ask: to what extent are human actions recorded as measurable signals in geological strata, and is the Anthropocene world markedly different from the stable Holocene Epoch of the last 11,700 years that allowed human civilization to develop?


The Holocene Epoch has been a time during which human societies advanced by gradually domesticating the land to increase food production, built urban settlements and became proficient at developing the water, mineral and energy resources of the planet. The proposed Anthropocene Epoch, however, is marked as a time of rapid environmental change brought on by the impact of a surge in human population and increased consumption during the 'Great Acceleration' of the mid-20th century.


Dr Colin Waters of the British Geological Survey said: "Humans have long affected the environment, but recently there has been a rapid global spread of novel materials including aluminium, concrete and plastics, which are leaving their mark in sediments. Fossil-fuel combustion has dispersed fly ash particles worldwide, pretty well coincident with the peak distribution of the 'bomb spike' of radionuclides generated by atmospheric testing of nuclear weapons." "All of this shows that there is an underlying reality to the Anthropocene concept", commented Jan Zalasiewicz of the University of Leicester, a co-author and working group Chair.


The study, co-authored by 24 members of the Anthropocene Working Group, shows that humans have changed the Earth system sufficiently to produce a range of signals in sediments and ice, and these are sufficiently distinctive to justify recognition of an Anthropocene Epoch in the Geological Time Scale. In 2016 the Anthropocene Working Group will gather more evidence on the Anthropocene, which will help inform recommendations on whether this new time unit should be formalized and, if so, how it might be defined and characterized.


A number of UK members of the group have contributed to this study, Colin Waters (lead author and Secretary of the group) and Michael Ellis, both from the British Geological Survey, Jan Zalasiewicz, Mark Williams and Matt Edgeworth from Leicester University and Colin Summerhayes from Cambridge University have provided significant input to this study and maintain the UK's strong involvement in research into the Anthropocene concept.

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Climate change, past and present - comparing the Ice Age with current change

Climate change, past and present - comparing the Ice Age with current change | Amazing Science | Scoop.it

Some people wonder if the current climate change has "natural causes". They sometimes refer to the changes during the 'Ice Age' and think the current events must be natural as well. However, that is not the case. The current situation is different. The graph shows that carbon dioxide in the air has increased and decreased over hundreds of  thousands of years. The recent increase in carbon dioxide is much bigger and faster than the natural changes.


The low readings match with times called 'glacial stages'. During glacial stages, ice covered large areas of the Earth. The most recent glacial stage occurred between 115,000 and 11,500 years ago. The peaks in the graph show times when carbon dioxide was high. Those times are called 'interglacial stages'Glacial and interglacial stages are linked to regular patterns in the movements of the Earth. The Earth's movements cause warming or cooling. This changes the amount of carbon dioxide that can dissolve in the oceans. So in that early phase, the temperature rises first, before the CO2 level rises. As the Earth warms, more carbon dioxide leaves the oceans. The extra gas in the air boosts the warming effect.


The Milankovitch Cycles are tending to cool the Earth. So the current warming is not part of natural processes. Global temperatures are only just beginning to respond to the recent big increase in carbon dioxide.


The extra carbon dioxide has come mainly from burning fossil fuels. The rise in carbon dioxide now means the cycle of glacial and interglacial stages may have been broken. A research paper has looked at that issue: "...the end of the current interglacial would occur within the next 1500 years, if atmospheric CO2 concentrations did not exceed 240±5ppmv.So carbon dioxide would need to drop way below the current level for this interglacial to end.

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Auroral mystery solved: Sudden bursts caused by swirling charged particles

Auroral mystery solved: Sudden bursts caused by swirling charged particles | Amazing Science | Scoop.it
Auroras are dimly present throughout the night in polar regions, but sometimes these lights explode in brightness. Now Japanese scientists have unlocked the mystery behind this spectacle, known as auroral breakup.

For years, scientists have contemplated what triggers the formation of auroral substorms and the sudden bursts of brightness. Appearing in the Journal of Geophysical Research, the current study overthrows existing theories about the mechanism behind this phenomenon.

The Kyoto-Kyushu research team has revealed that hot charged particles, or plasmas, gather in near-Earth space -- just above the upper atmosphere of the polar region -- when magnetic field lines reconnect in space. This makes the plasma rotate, creating a sudden electrical current above the polar regions. Furthermore, an electric current overflows near the bright aurora in the upper atmosphere, making the plasma rotate and discharge the extra electricity. This gives rise to the "surge", the very bright sparks of light that characterize substorms.

"This isn't like anything that us space physicists had in mind," said study author Yusuke Ebihara of Kyoto University.

Ebihara based the study on a supercomputer simulation program developed by Takashi Tanaka, professor emeritus at Kyushu University.

Auroras originate from plasma from the sun, known as the solar wind. In the 1970s, scientists discovered that when this plasma approaches the Earth together with magnetic fields, it triggers a change in the Earth's magnetic field lines on the dayside, and then on the night side. This information alone couldn't explain how the fluttering lights emerge in the sky, however.

Scientists had come up with theories for separate parts of the process. Some suggested that acceleration of plasma from the reconnection of magnetic field lines caused auroral breakup. Others argued that the electrical current running near the Earth diverts a part of the electrical current into the ionosphere for some unknown reason, triggering the bright bursts of light. This theory was widely accepted because it offered an explanation for why upward-flowing currents emerged out of our planet. But the pieces of the puzzle didn't quite fit well together.

Tanaka's supercomputer simulation program, on the other hand, offers a logical explanation from start to finish.

"Previous theories tried to explain individual mechanisms like the reconnection of the magnetic field lines and the diversion of electrical currents, but there were contradictions when trying to explain the phenomena in its entirety," said Ebihara. "What we needed all along was to look at the bigger picture."
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First map of Earth's hidden groundwater

First map of Earth's hidden groundwater | Amazing Science | Scoop.it
Groundwater: it's one of the planet's most exploited, most precious natural resources. It ranges in age from months to millions of years old. Around the world, there's increasing demand to know how much we have and how long before it's tapped out.


For the first time since a back-of-the-envelope calculation of the global volume of groundwater was attempted in the 1970s, an international group of hydrologists has produced the first data-driven estimate of the Earth's total supply of groundwater. The study, led by Dr. Tom Gleeson of the University of Victoria with co-authors at the University of Texas at Austin, the University of Calgary and the University of Göttingen, was published today in Nature Geoscience.


The bigger part of the study is the "modern" groundwater story. The report shows that less than six per cent of groundwater in the upper two kilometres of the Earth's landmass is renewable within a human lifetime. "This has never been known before," says Gleeson. "We already know that water levels in lots of aquifers are dropping. We're using our groundwater resources too fast—faster than they're being renewed."


With the growing global demand for water—especially in light of climate change—this study provides important information to water managers and policy developers as well as scientists from fields such as hydrology, atmospheric science, geochemistry and oceanography to better manage groundwater resources in a sustainable way, he says.


Via Catherine Russell
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breanna mae johnson's curator insight, December 2, 2015 9:57 AM

This map may help people understand how much groundwater we actually have remaining. This could influence a better perception of water preservation and conservation. With the growing demand of water, people need to know how important it is to use our water wisely for the well-being of future generations.

 

                                                                                       BJ

Violet Knight's curator insight, December 2, 2015 9:59 AM

I believe that this is an important discovery. Now we will be able to conserve enough water to last us until our water supply is replenished. 

Raven Stroud's curator insight, December 3, 2015 10:20 AM

I think that if we do not limit ourselves when it comes to using groundwater, we could end up running out of it and that would cause many problems with the human race and with the environment. -R.S.

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Ancient river network discovered buried deep under Saharan sand

Ancient river network discovered buried deep under Saharan sand | Amazing Science | Scoop.it

Radar images of the Mauritanian desert have revealed a river stretching for more than 500km and suggest plants and wildlife once thrived there.


A vast river network that once carried water for hundreds of miles across Western Sahara has been discovered under the parched sands of Mauritania.


Radar images taken from a Japanese Earth observation satellite spotted the ancient river system beneath the shallow, dusty surface, apparently winding its way from more than 500km inland towards the coast.


The buried waterway may have formed part of the proposed Tamanrasett River that is thought to have flowed across parts of Western Sahara in ancient times from sources in the southern Atlas mountains and Hoggar highlands in what is now Algeria.


The French-led team behind the discovery believe the river carried water to the sea during the periodic humid spells that took hold in the region over the past 245,000 years. Water may last have coursed through the channels 5,000 years ago.


The river would have helped people, plants and wildlife to thrive in what is now desert land, and would have carried nutrients crucial for marine organisms far into the sea. Were it still flowing today, the river system would rank 12th among the largest on Earth, the researchers write in the journal Nature Communications.


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Scientists find link between comet and asteroid showers & mass extinctions

Scientists find link between comet and asteroid showers & mass extinctions | Amazing Science | Scoop.it

Mass extinctions occurring over the past 260 million years were likely caused by comet and asteroid showers, scientists conclude in a new study published in Monthly Notices of the Royal Astronomical Society.

For more than 30 years, scientists have argued about a controversial hypothesis relating to periodic mass extinctions and impact craters - caused by comet and asteroid showers - on Earth.


In their MNRAS paper, Michael Rampino, a New York University geologist, and Ken Caldeira, a scientist in the Carnegie Institution's Department of Global Ecology, offer new support linking the age of these craters with recurring mass extinctions of life, including the demise of the dinosaurs. Specifically, they show a cyclical pattern over the studied period, with both impacts and extinction events taking place every 26 million years.


This cycle has been linked to periodic motion of the Sun and planets through the dense mid-plane of our galaxy. Scientists have theorized that gravitational perturbations of the distant Oort comet cloud that surrounds the Sun lead to periodic comet showers in the inner solar system, where some comets strike the Earth.


To test their hypothesis, Rampino and Caldeira performed time-series analyses of impacts and extinctions using newly available data offering more accurate age estimates.


"The correlation between the formation of these impacts and extinction events over the past 260 million years is striking and suggests a cause-and-effect relationship," says Rampino.


Specifically, he and Caldeira found that six mass extinctions of life during the studied period correlate with times of enhanced impact cratering on Earth. One of the craters considered in the study is the large (180 km diameter) Chicxulub impact structure in the Yucatan, which dates to about 65 million years ago—the time of a great mass extinction that included the dinosaurs.


Moreover, they add, five out of the six largest impact craters of the last 260 million years on earth correlate with mass extinction events. "This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet," Rampino observes.


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What are some of the best rare natural phenomena that occur on Earth?

What are some of the best rare natural phenomena that occur on Earth? | Amazing Science | Scoop.it
Answer (1 of 84): Lake Hillier, in Western Australia, is pink. Nobody seems to be able to definitively explain its distinctive (and very cool looking) color.
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Globally unique double crater identified in Sweden: Impact 460 million years ago

Globally unique double crater identified in Sweden: Impact 460 million years ago | Amazing Science | Scoop.it

Researchers at the University of Gothenburg have found traces of two enormous meteorite impacts in the Swedish county of Jämtland, a twin strike that occurred around 460 million years ago.

The researchers have discovered two craters in Jämtland. One is enormous, while the other is a tenth of the size of the first. "The two meteorite impacts occurred at the same time, 458 million years ago, and formed these two craters," says Erik Sturkell, Professor of Geophysics at the University of Gothenburg.

Erik Sturkell and his research colleagues found one of the craters 20 kilometres south of Östersund in Brunsflo. This is an enormous crater, with a diameter of 7.5 kilometers. The smaller crater is located 16 kilometers from there, and has a diameter of 700 meters.


The two meteorite impacts 458 million years ago were not the only ones to strike Earth at this time. "Around 470 million years ago, two large asteroids collided in the asteroid belt between Mars and Jupiter, and many fragments were thrown off in new orbits. Many of these crashed on Earth, such as these two in Jämtland," says Erik Sturkell.


Jämtland was under the sea at the time, with a water depth of 500 meters at the points where two meteorites simultaneously stuck. Double impacts like this are very unusual. This is the first double impact on Earth that has been conclusively proved. "Information from drilling operations demonstrates that identical sequences are present in the two craters, and the sediment above the impact sequences is of the same age. In other words, these are simultaneous impacts," says Erik Sturkell. The water was forced away during the impact, and for a hundred seconds these enormous pits were completely dry.


"The water then rushed back in, bringing with it fragments from the meteorites mixed with material that had been ejected during the explosion and with the gigantic wave that tore away parts of the sea bed," says Erik Sturkell.

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Revealed: How did our planet ever escape 'snowball Earth'?

Revealed: How did our planet ever escape 'snowball Earth'? | Amazing Science | Scoop.it
Glaciers once covered most of Earth's surface and reflected the sun's heat back into space.


New details of a nightmare period on Earth with surface conditions as frigid as present-day central Antarctica at the equator have been revealed thanks to the publication of a study of ancient glacier water. The research, by an international team led by Daniel Herwartz, is published in the journal Proceedings of the National Academy of Sciences and shows that even tropical regions were once covered in snow and ice.


The idea of a deep-frozen world, “snowball Earth”, has captured the imagination since first proposed in the 1990s. On several occasions in history, long before animals evolved, apparently synchronous ice sheets existed on all the continents. However, much like falling into a crevasse on a glacier, it’s easy enough to enter such an ice age, but very difficult to escape.


The snowball Earth theory came from climate modelers who found that low carbon dioxide levels could trigger the growth of ice sheets. The whole planet would become glaciated and its mean temperature drop to as low as -45°C. As ice is much more reflective than the sea, or bare land, the Earth at that point would have been bouncing nearly all of the sun’s radiation back into space. So how could the planet ever emerge from such an ice age?


Volcanoes had to be the answer. Only they could emit enough carbon dioxide into the atmosphere to overcome the effects of Earth’s cool reflective surface. But climate models still found it difficult to plausibly describe how the Earth could have shed its glaciers.


We now have the first full explanation for how the best-known snowball event, the Marinoan, finished 635 million years ago with a several hundred meter rise in sea level. The study is the result of work by an international team of scientists. The results are published in the journal Nature Geoscience.


The team of researchers found slight wobbles of the Earth’s spin axis caused differences in the heat received at different places on the planet’s surface. These changes were small, but enough over thousands of years to cause a change in the places where snow accumulated or melted, leading the glaciers to advance and retreat.


The Earth was left looking just like the McMurdo Dry Valleys in Antarctica – arid, with lots of bare ground, but also containing glaciers up to 3 km thick. Such an Earth would have been darker than previously envisaged, absorbing more of the sun’s radiation; it was easier to see how the escape from the snowball happened.


Today, to find exposed rocks that can tell us about the carbon dioxide content of the atmosphere in the Marinoan, you have to go to the Norwegian Arctic island of Svalbard. In 2009 snowball theory was vindicated after we found the telltale signal of high carbon dioxide levels in Svalbard limestone that formed during the ice age.


Immediately underneath the Marinoan deposits are some beds of rocks deposited at very regular intervals – so regular that they must have formed over thousands of years, influenced by wobbles in the Earth’s orbit. Since Svalbard was near the Equator at the time, the most likely type of wobble is caused by the Earth slowly shifting (“precessing”) its axis on cycles of approximately 20,000 years.


Researchers also found evidence of the same process in the Snowball deposits themselves. Fluctuations in ice in relation to the Earth’s orbit are a feature of our modern ice ages over the past million years, but had not been found in such an old glaciation.


For a long time the Earth was too cold for glaciers to erode and deposit sediment – the main snowball period. The sediments then show several advances and retreats of the ice. When the glaciers retreated, they left behind a patchwork of environments: shallow and deep lakes, river channels, and floodplains that appeared as arid as anything known in Earth’s history.


Carbon dioxide appears to have remained at the same high level throughout the deposition of these sediments. Since it takes millions of years for CO2 to build up in the atmosphere, this implies the sediment layers must have formed quickly – on the order of 100,000 years. All this fits with the idea of 20,000 year precession cycles.


group of climate modellers from Paris tested the theory. The rocks and the models agreed: wobbles in the Earth’s axis had caused the planet to escape its snowball phase.


So after several million years of being frozen, this icy Earth with a hot atmosphere rich in carbon dioxide had reached a Goldilocks zone – too warm to stay completely frozen, too cold to lose its ice. This transitional period lasted around 100,000 years before the glaciers fully melted and present-day Svalbard was flooded by the sea.

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Meteorite Impacts Can Create DNA Building Blocks

Meteorite Impacts Can Create DNA Building Blocks | Amazing Science | Scoop.it

The emergence of life's building blocks on the prebiotic Earth was the first crucial step for the origins of life. Extraterrestrial delivery of intact amino acids and nucleobases is the prevailing hypothesis for their availability on prebiotic Earth because of the difficulties associated with the production of these organics from terrestrial carbon and nitrogen sources under plausible prebiotic conditions. However, the variety and amounts of these intact organics delivered by meteorites would have been limited. Previous shock–recovery experiments have demonstrated that meteorite impact reactions could have generated organics on the prebiotic Earth.


A new study shown that meteorite impacts on ancient oceans may have created nucleobases and amino acids. Researchers from Tohoku University, National Institute for Materials Science and Hiroshima University discovered this after conducting impact experiments simulating a meteorite hitting an ancient ocean. A new study shown that meteorite impacts on ancient oceans may have created nucleobases and amino acids. Researchers from Tohoku University, National Institute for Materials Science and Hiroshima University discovered this after conducting impact experiments simulating a meteorite hitting an ancient ocean. 


Via Integrated DNA Technologies
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