'Crystal Clocks' Used to Time Magma Storage Before Volcanic Eruptions

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-0fPah00EClI/XTNAIDF8lPI/AAAAAAAARQo/qC48OZfgFgcoHnkeIxhqn8F2GebjB20twCLcBGAs/s1600/%2527Crystal%2BClocks%2527%2BUsed%2Bto%2BTime%2BMagma%2BStorage%2BBefore%2BVolcanic%2BEruptions%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="'Crystal Clocks' Used to Time Magma Storage Before Volcanic Eruptions" border="0" data-original-height="867" data-original-width="1299" height="426" src="https://1.bp.blogspot.com/-0fPah00EClI/XTNAIDF8lPI/AAAAAAAARQo/qC48OZfgFgcoHnkeIxhqn8F2GebjB20twCLcBGAs/s640/%2527Crystal%2BClocks%2527%2BUsed%2Bto%2BTime%2BMagma%2BStorage%2BBefore%2BVolcanic%2BEruptions%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Zircon. Photo: MicrolabNW</td></tr> </tbody></table> <br /> The molten rock that feeds volcanoes can be stored in the Earth's crust for as long as a thousand years, a result which may help with volcanic hazard management and better forecasting of when eruptions might occur.<br /> <br /> Researchers from the University of Cambridge used volcanic minerals known as 'crystal clocks' to calculate how long magma can be stored in the deepest parts of volcanic systems. This is the first estimate of magma storage times near the boundary of the Earth's crust and the mantle, called the Moho. The results are reported in the journal Science.<br /> <br /> "This is like geological detective work," said Dr Euan Mutch from Cambridge's Department of Earth Sciences, and the paper's first author. "By studying what we see in the rocks to reconstruct what the eruption was like, we can also know what kind of conditions the magma is stored in, but it's difficult to understand what's happening in the deeper parts of volcanic systems."<br /> <br /> "Determining how long magma can be stored in the Earth's crust can help improve models of the processes that trigger volcanic eruptions," said co-author Dr John Maclennan, also from the Department of Earth Sciences. "The speed of magma rise and storage is tightly linked to the transfer of heat and chemicals in the crust of volcanic regions, which is important for geothermal power and the release of volcanic gases to the atmosphere."<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> The researchers studied the Borgarhraun eruption of the Theistareykir volcano in northern Iceland, which occurred roughly 10,000 years ago, and was fed directly from the Moho. This boundary area plays an important role in the processing of melts as they travel from their source regions in the mantle towards the Earth's surface. To calculate how long the magma was stored at this boundary area, the researchers used a volcanic mineral known as spinel like a tiny stopwatch or crystal clock.<br /> <br /> Using the crystal clock method, the researchers were able to model how the composition of the spinel crystals changed over time while the magma was being stored. Specifically, they looked at the rates of diffusion of aluminium and chromium within the crystals and how these elements are 'zoned'.<br /> <br /> "Diffusion of elements works to get the crystal into chemical equilibrium with its surroundings," said Maclennan. "If we know how fast they diffuse we can figure out how long the minerals were stored in the magma."<br /> <br /> The researchers looked at how aluminium and chromium were zoned in the crystals, and realised that this pattern was telling them something exciting and new about magma storage time. The diffusion rates were estimated using the results of previous lab experiments. The researchers then used a new method, combining finite element modelling and Bayesian nested sampling to estimate the storage timescales.<br /> <br /> "We now have really good estimates in terms of where the magma comes from in terms of depth," said Mutch. "No one's ever gotten this kind of timescale information from the deeper crust."<br /> <br /> Calculating the magma storage time also helped the researchers determine how magma can be transferred to the surface. Instead of the classical model of a volcano with a large magma chamber beneath, the researchers say that instead, it's more like a volcanic 'plumbing system' extending through the crust with lots of small 'spouts' where magma can be quickly transferred to the surface.<br /> <br /> A second paper by the same team, recently published in Nature Geoscience, found that that there is a link between the rate of ascent of the magma and the release of CO₂, which has implications for volcano monitoring.<br /> <br /> The researchers observed that enough CO₂ was transferred from the magma into gas over the days before eruption to indicate that CO₂ monitoring could be a useful way of spotting the precursors to eruptions in Iceland. Based on the same set of crystals from Borgarhraun, the researchers found that magma can rise from a chamber 20 kilometres deep to the surface in as little as four days.<br /> <br /> <br /> <u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="https://www.cam.ac.uk/research/news/crystal-clocks-used-to-time-magma-storage-before-volcanic-eruptions" rel="nofollow" target="_blank">Materials</a> provided by <a href="http://www.cam.ac.uk/" rel="nofollow" target="_blank">University of Cambridge</a>. </span></i></u><span style="background-color: white; color: #333333; display: inline; float: none; font-family: "helvetica neue" , "helvetica" , "arial" , sans-serif; font-size: 14px; font-style: normal; font-weight: 400; letter-spacing: normal; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><br /> </span></div>

'Crystal Clocks' Used to Time Magma Storage Before Volcanic Eruptions

Zircon. Photo: MicrolabNW The molten rock that feeds volcanoes can be stored in the Earth's crust for as long as a thousand years,...

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California Was Shaking Again Tuesday, With Six Earthquakes of 3.5 or Greater

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-p7gzyeoWe_w/XS9GWJrIxmI/AAAAAAAARQM/RtwNKt4DHyo_TBi3dLl8A_hz9UtdkLO0QCLcBGAs/s1600/California%2BWas%2BShaking%2BAgain%2BTuesday%252C%2BWith%2BSix%2BEarthquakes%2Bof%2B3.5%2Bor%2BGreater%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="California Was Shaking Again Tuesday, With Six Earthquakes of 3.5 or Greater" border="0" data-original-height="554" data-original-width="1204" height="294" src="https://1.bp.blogspot.com/-p7gzyeoWe_w/XS9GWJrIxmI/AAAAAAAARQM/RtwNKt4DHyo_TBi3dLl8A_hz9UtdkLO0QCLcBGAs/s640/California%2BWas%2BShaking%2BAgain%2BTuesday%252C%2BWith%2BSix%2BEarthquakes%2Bof%2B3.5%2Bor%2BGreater%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Photo: USGS</td></tr> </tbody></table> <br /> <br /> <div style="text-align: left;"> California was struck by six earthquakes of a 3.5-magnitude or greater over a 24-hour period beginning Tuesday morning, according to the US Geological Survey. One of those struck the San Francisco Bay area at a magnitude 4.3. Another -- a strong 4.5-magnitude -- jolted Ridgecrest around the same time, the US Geological Survey reported.<br /> <br /> A magnitude 4.3 earthquake shook the eastern San Francisco Bay area at 1:11 p.m. Tuesday.<br /> <br /> Four minutes later, a magnitude 4.5 quake hit near Ridgecrest, which, earlier this month, was rattled by a pair of massive temblors, including the most powerful shaker (a magnitude 7.1) to strike California in 20 years.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> And, then, at 1:24 p.m., the Bay Area felt another rumble, this time a magnitude 3.2, again centered near Blackhawk, an unincorporated community east of Oakland. It was originally reported as a magnitude 3.5.<br /> <br /> Does this mean "The Big One" is coming? Don't panic, the U.S. Geographical Survey cautioned.<br /> <br /> "This specific sequence of earthquakes — the ones in Ridgecrest and the ones in Blackhawk — are not indicative that 'The Big One' is coming," said Rafael Abreu, a geophysicist with the USGS National Earthquake Information Center in Colorado.<br /> <br /> There were no immediate reports of damage or injuries after any of Tuesday's quakes.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">Were the earthquakes connected? </span></h4> <div style="text-align: left;"> No. The earthquakes near Blackhawk are a different set from the aftershocks following the 7.1 Ridgecrest event on July 5, Abreu said.<br /> <br /> They also occurred near different fault lines. About 270 miles lies between the centers of the quakes in northern and southern California. <br /> <br /> The Ridgecrest quake occurred near the Little Lake fault zone, according to USGS maps. Geophysicists recorded the Blackhawk quakes near the Greenville fault zone. Neither are connected and both have a slip rate of 1 to 5 mm a year. <br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> By comparison, the San Andreas Fault, which serves as a tectonic boundary between the North American and Pacific plates, moves more than 5 mm per year. California has gone past the average time between large earthquakes along the San Andreas, leading some to say the area is overdue for a massive temblor. </div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">Is California experiencing an unusual number of earthquakes? </span></h4> <div style="text-align: left;"> This is all normal, according to the USGS.<br /> <br /> "We're having quakes exactly where, geographically speaking, we'd expect these quakes to happen," Abreu said. "And we're having the amount of earthquakes we'd expect to see." <br /> <br /> In terms of magnitude and number of quakes, Abreu said the Ridgecrest sequence has actually decayed faster than expected, but the variation isn't unusual for the geological setting. <br /> <br /> Four other quakes registering a 3.5 magnitude or above occurred in the Ridgecrest area Tuesday: one in the early morning, one in the afternoon, and two at night.  </div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">What are the aftershock predictions? </span></h4> <div style="text-align: left;"> Northern California has a 4% chance of one or more earthquakes stronger than magnitude 4.3 over the next week, the USGS said. Smaller earthquakes are likely over the same time period, with 0 to 5 magnitude 3 or higher aftershocks predicted near Blackhawk. <br /> <br /> For the Ridgecrest sequence, the USGS last updated its predictions on Monday. Geophysicists recorded 524 magnitude 3 or higher earthquakes and 5 magnitude 5 or higher earthquakes since July 5. The first group are strong enough to be felt while the second can do damage. </div> <div style="text-align: left;"> <br /></div> </div>

California Was Shaking Again Tuesday, With Six Earthquakes of 3.5 or Greater

Photo: USGS California was struck by six earthquakes of a 3.5-magnitude or greater over a 24-hour period beginning Tuesday morning, ...

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Ringing Rocks A Geological and Musical Marvel

<div dir="ltr" style="text-align: left;" trbidi="on"><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-JDDIQLGd5ow/XS31ILXBRgI/AAAAAAAARQA/kRfx_0qxlagqwt_hBLnyImh3l8g3I51IgCLcBGAs/s1600/Ringing%2BRocks%2BA%2BGeological%2Band%2BMusical%2BMarvel%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Ringing Rocks A Geological and Musical Marvel" border="0" data-original-height="779" data-original-width="1200" height="414" src="https://1.bp.blogspot.com/-JDDIQLGd5ow/XS31ILXBRgI/AAAAAAAARQA/kRfx_0qxlagqwt_hBLnyImh3l8g3I51IgCLcBGAs/s640/Ringing%2BRocks%2BA%2BGeological%2Band%2BMusical%2BMarvel%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Ringing Hill Park. Photo: Sherry M/TripAdvisor</td></tr> </tbody></table><br /> Although scientists don’t have a definitive answer as to why the rocks ring, they do have a name for ringing rocks. They are called with sonorous rocks or lithophonic rocks. These are the terms that are given to rocks that resonate with a bell-like sound when they are struck. <br /> <br /> Sonorous rocks are rocks that resonate like a bell when struck. These chime-like sounds come from geological phenomena known as ringing rocks. Physically, they look no different from regular rocks, but it’s not until you lightly strike them with a hammer that the rocks reveal their sonic secret.<br /> <br /> Stones do not usually ring, but when these particular stones are struck lightly with a hammer, they will vibrate and make a sound not unlike that of a bell. Why they do this is still a mystery to science. The rocks themselves are composed of diabase, the same type of rock that makes up most the earth's crust. Another part of the mystery is while all the rocks seem to be made of the same material (mostly iron and hard minerals) only one-third of them generate the ringing sound when hit. Rocks that ring are known as "live" rocks, and those that don't are referred to as "dead" rocks.<br /> <div style="margin: 0px auto; width: 100%;"><script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /> </div>Although there have been over a dozen diabase ringing rock boulder fields identified in the Pennsylvania/New Jersey area, the majority are either on private property or have been obliterated by urban development. <span style="font-family: "georgia" , "times new roman" , serif;">There are three sites north of Philadelphia</span> which are readily accessible to the public: Ringing Rocks County Park, Stony Garden, and Ringing Hill Park.<br /> <h4 style="text-align: left;"><span style="font-family: "georgia" , "times new roman" , serif;">Geology:</span></h4>These boulder field in southeastern Pennsylvania and central New Jersey formed from a group of diabase sills in Newark Basin. The sills were formed when stretching of the Earth's crust allowed mafic magma to travel up from the upper mantle inject into the sedimentary basin 200 million years ago (early Jurassic Period).<br /> <br /> The basal olivine unit is similar to the one found in the Palisades Sill in New Jersey and New York. The olivine diabase unit is significantly harder, denser, and more resistant to weathering than the upper portions of the diabase sill.<br /> <br /> Most observers did not make the distinction between the upper "normal". diabase which is found over wide areas, and the thin olivine diabase unit found at the base of the sills which actually produces the ringing rock boulder fields. A main factor in the confusion is the outward appearance of the rocks. Both the normal and olivine diabase rocks are dark grey to black in color. Microscopic examination is often required o identify the differences.<br /> <br /> Although the Newark series diabase sills crop out in a belt throughout the length of the Appalachian Mountains, only a narrow band of outcrops in southeastern Pennsylvania and New Jersey develop ringing rock boulder fields. The probable reason is that these areas were at the southern edge of the Pleistocene glaciers, and would have been subject to extreme periglacial conditions. Periglacial boulder fields are a common feature in Pennsylvania and New Jersey.<br /> <br /> All of the observed ringing rock boulder fields in southeastern Pennsylvania and New Jersey are a form of felsenmeer. These barren block fields occur in periglacial environments where outcrops of resistant rock are exposed with a slope of less than 25°. Frost wedging breaks up the upper portion of the rock formation, and the slight dip of the field allows the fine weathering materials to be flushed away before soil can develop. <br /> <div style="margin: 0px auto; width: 100%;"><script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /> </div><h4 style="text-align: left;"><span style="font-family: "georgia" , "times new roman" , serif;">What We Know About the Rocks’ Ringing Ability: </span></h4>There has been a great deal of controversy concerning the ringing ability of the boulders; conversely, there has been an almost complete lack of testing to support the conjectures. Conditions such as size and shape of the boulders and the way that the boulders are supported or stacked certainly influence the sounds that the boulders make but do not in themselves impart the ringing ability.<br /> <br /> Although the sound is often described as metallic, it is most likely due to a combination of the density of the rock and a high degree of internal stress. The sound can be duplicated on a small scale by tapping the handle of a ceramic coffee cup.<br /> <br /> The iron content of the diabase is often identified as the source of the ringing ability. Actual chemical analysis of the Coffman Hill diabase shows that iron content (as ferric oxide) of the rock ranges from 9% and 12%. Although comparatively high for an average igneous rock (3% is typical for granite), it is within the normal range for a basalt. This point suggests that the iron content is not a primary factor in the ringing ability.<br /> <br /> So far, there has been only one published scientific experiment on the source of the ringing ability. In the 1960s, a Rutgers University professor did an informal experiment where specimens of "live" and "dead" ringing rock boulders from the Bucks County park site were sawed into thin slices and then measured for changes in shape. The rock slices were measured with delicate foil strain gauges, which could measure minute changes in size. <br /> <br /> A more plausible theory is that the elastic stresses remained in the rock when the boulder fields formed, and the slow weathering rate keeps the stresses from dissipating. A possible source of the stresses would likely be the loading stresses from the time when the rock crystallized. The diabase sill formed at roughly 1.2–1.9 miles (2–3 km) beneath the surface.<br /> <br /> This "relict stress" theory implies that the ringing rock boulders act much like a guitar string. When a guitar string is limp it does not resonate, but a plucked string will provide a range of sounds depending on the level of applied tension.<br /> <b><span style="font-family: "georgia" , "times new roman" , serif;"><br /> </span></b> <b><span style="font-family: "georgia" , "times new roman" , serif;">Video:</span></b><br /> <style>.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }</style><div class='embed-container'><iframe src='https://www.youtube.com/embed/fBiVt1pKnAQ' frameborder='0' allowfullscreen></iframe></div><br /> <b><span style="font-family: "georgia" , "times new roman" , serif;">See also: </span></b><br /> <a href="https://www.geologyin.com/2018/10/chrysanthemum-stone-natural-flower-stone.html" target="_blank">Chrysanthemum Stone: Natural Flower Stone</a><br /> <a href="https://www.geologyin.com/2018/04/the-mysterious-living-stones-of-romania.html" target="_blank">The Mysterious Living Stones of Romania: They Grow and Move</a><br /> <div __gwt_cell="cell-gwt-uid-3226" style="outline-style: none;"><a href="https://www.geologyin.com/2017/11/how-utahs-mysterious-moqui-marbles.html" target="_blank">How Utah's Mysterious Moqui Marbles Formed?</a></div></div>

Ringing Rocks A Geological and Musical Marvel

Ringing Hill Park. Photo: Sherry M/TripAdvisor Although scientists don’t have a definitive answer as to why the rocks ring, they do have...

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What Delayed Earth’s Oxygenation?

<div dir="ltr" style="text-align: left;" trbidi="on"><div class="separator" style="clear: both; text-align: center;"><a href="https://1.bp.blogspot.com/-00z0jljF4zU/XSytFLHBGyI/AAAAAAAARPo/dIQlFRUCu7QAVqL6kVgiUeXM064hd0sMQCLcBGAs/s1600/What%2BDelayed%2BEarth%25E2%2580%2599s%2BOxygenation.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img alt="What Delayed Earth’s Oxygenation?" border="0" data-original-height="964" data-original-width="1200" height="512" src="https://1.bp.blogspot.com/-00z0jljF4zU/XSytFLHBGyI/AAAAAAAARPo/dIQlFRUCu7QAVqL6kVgiUeXM064hd0sMQCLcBGAs/s640/What%2BDelayed%2BEarth%25E2%2580%2599s%2BOxygenation.jpg" title="" width="640" /></a></div><br /> <br /> Powering a massive biosphere on Earth, photosynthesis is the light-mediated reaction that converts carbon dioxide and water to carbohydrates and oxygen. About 2.3 billion years ago, this reaction led to a dramatic oxygenation of Earth’s atmosphere.<br /> <br /> Evidence exists for oxygen-releasing photosynthesis evolving much earlier – perhaps as early as 3 billion years ago. However, the oxygen-rich atmosphere we take for granted today has existed for only about 10% of Earth’s 4.5-billion-year history. Why did oxygenation of the atmosphere occur so much later than the evolution of oxygen-releasing photosynthesis?<br /> <br /> “The striking lag has remained an enduring puzzle in the fields of Earth history and planetary science,” says Christopher Reinhard, an assistant professor in the School of Earth and Atmospheric Sciences (EAS).<br /> <br /> Reinhard, former EAS postdoctoral researcher Kazumi Ozaki, and collaborators have proposed a solution to the puzzle. Their findings, published in Nature Communications, suggest that in the oceans of early Earth, oxygen-releasing photosynthesizers could not compete effectively with their primitive counterparts.<br /> <div style="margin: 0px auto; width: 100%;"><script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /> </div>Modern photosynthesizers consume water and release oxygen. Primitive ones instead consume dissolved iron ions – which would have been abundant in the oceans of early Earth. They produce rust as a byproduct instead of oxygen.<br /> <br /> Using experimental microbiology, genomics, and large-scale biogeochemical modeling, “we found that photosynthetic bacteria that use iron instead of water are fierce competitors for light and nutrients,” says Ozaki, the paper’s first author and now an assistant professor in the Department of Environmental Science at Toho University, in Japan. “We propose that their ability to outcompete oxygen-producing photosynthesizers is an important component of Earth’s global oxygen cycle.”<br /> <br /> The study is part of Reinhard’s research goal to understand how the evolution of the photosynthetic biosphere controlled the composition of Earth’s atmosphere. “We want to understand the timing of major biological innovations and their impact on the chemistry of Earth’s oceans and atmosphere. We consider these principles to be central in understanding our own evolutionary origins and the search for life beyond our solar system.”<br /> <br /> “Our results contribute to a deeper knowledge of the biological factors controlling the long-term evolution of Earth’s atmosphere,” Ozaki says. “They offer a better mechanistic understanding of the factors that promote oxygenation of the atmospheres of Earth-like planets beyond our solar system.” The results “yield an entirely new vantage from which to build theoretical models of Earth’s biogeochemical oxygen cycle,” Reinhard adds. <br /> <br /> <br /> <u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="https://www.news.gatech.edu/2019/07/09/what-delayed-earths-oxygenation" rel="nofollow" target="_blank">materials </a>provided by <a href="https://www.gatech.edu/" rel="nofollow" target="_blank">Georgia Tech.</a></span></i></u></div>

What Delayed Earth’s Oxygenation?

Powering a massive biosphere on Earth, photosynthesis is the light-mediated reaction that converts carbon dioxide and water to carbohydrat...

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Geoscientists Were Wrong About the 'World's Largest Volcano'

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-aaz7syH6FTw/XStN2d7EwwI/AAAAAAAARPQ/T6M69BeQWKUnBDkeHgv4V99jyuNbTEyIACLcBGAs/s1600/The%2BMauna%2BLoa%2Bshares%2Bthe%2Bproperties%2Bof%2Bisland%2Barc%2Bvolcanos%252C%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Geoscientists Were Wrong About the 'World's Largest Volcano'" border="0" data-original-height="802" data-original-width="1200" height="426" src="https://1.bp.blogspot.com/-aaz7syH6FTw/XStN2d7EwwI/AAAAAAAARPQ/T6M69BeQWKUnBDkeHgv4V99jyuNbTEyIACLcBGAs/s640/The%2BMauna%2BLoa%2Bshares%2Bthe%2Bproperties%2Bof%2Bisland%2Barc%2Bvolcanos%252C%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">The Mauna Loa </td></tr> </tbody></table> <br /> <span style="font-family: "georgia" , "times new roman" , serif;">An Unexpected Discovery Just Changed The Ranking of Earth's Biggest Volcano</span><br /> <br /> <span style="font-family: Georgia, "Times New Roman", serif;">Congratulations Mauna Loa, on the island of Hawaii: you are once more the biggest shield volcano on the planet, without even having done anything. New research suggests the previous record holder, Tamu Massif in the northwest Pacific Ocean, should be disqualified on a technicality.</span><br /> <br /> <div style="text-align: left;"> <span style="font-family: inherit;"><span style="font-family: "georgia" , "times new roman" , serif;">The discovery of Tamu Massif, a gigantic volcano located about 1,000 miles east of Japan, made big news in 2013 when researchers reported it was the largest single volcano documented on earth, roughly the size of New Mexico.</span></span><br /> <br /> New findings, reported this week in Nature Geoscience, conclude that it is a different breed of volcanic mountain than earlier thought, throwing into doubt the prior claim that it is the world's largest single volcano.<br /> <br /> The study analyzed magnetic field data over Tamu Massif, finding that magnetic anomalies -- perturbations to the field caused by magnetic rocks in the Earth's crust -- resemble those formed at mid-ocean ridge plate boundaries.<br /> <br /> William Sager, a geophysicist at the University of Houston and senior author for the paper, said the discovery led researchers to conclude that Tamu Massif formed by mid-ocean ridge "spreading," the geologists' term for creation of ocean crust at mid-ocean ridge plate boundaries, rather than as a shield volcano, as previously thought. Shield volcanos are formed primarily as stacks of fluid lava flows and are one of the most common types of volcano.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> An international group of researchers -- from Texas, China and Japan -- sought to understand how the massive Tamu Massif volcano formed near the nexus of three spreading ridges. The key, they report, is magnetic anomalies.<br /> <br /> Mid-ocean ridges -- plate boundaries where oceanic plates move apart -- are themselves large volcanoes. These ridges record distinctive linear magnetic anomalies, parallel to the ridge, as they form new crust. This is a result of lava flows and magma being concentrated near the ridge axis where the magnetic minerals in the new crust record reversals of the magnetic field polarity.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">A New Understanding of Tamu Massif</span></h4> <div style="text-align: left;"> Linear magnetic anomalies formed by the three ridges had previously been found around Tamu Massif, but it was unclear where they stopped within the volcano. A paper published in 2013 by Sager and colleagues concluded that Tamu Massif is an enormous shield volcano, formed by far-reaching lava flows emanating from its summit.<br /> <br /> The latest study compiled a magnetic anomaly map over Tamu Massif, using 4.6 million magnetic field readings collected over 54 years along 72,000 kilometers of ship tracks. The data set was anchored by a new grid of magnetic profiles, positioned with modern GPS navigation, collected by the study authors using the Schmidt Ocean Institute ship Falkor. The resulting map shows that linear magnetic anomalies around Tamu Massif blend into linear anomalies over the mountain itself -- implying that the underwater volcano formed by extraordinary mid-ocean ridge crustal formation.<br /> <br /> Sager said the finding is important because it demonstrates that Tamu Massif and other oceanic plateaus are formed by a different process than previously thought. A widely-accepted model suggests a large blob of magma, known as a "mantle plume," rises through the mantle and creates a massive volcano when it arrives at the surface. This eruption is thought to be analogous to massive eruptions on land, called "continental flood basalts" and it creates a vertical succession of lava flows.<br /> <br /> The ocean-ridge-spreading hypothesis suggests the age progression is instead lateral. New material is always added at the center of the ridge as older material drifts laterally away. An implication is that the gradual slopes of Tamu Massif are not caused by lava flow shape but instead by a gradual inflation and then deflation of ridge volcanism as the crust became thicker and then grew thinner.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> The new finding also weakens the accepted analogy between eruptions of continental flood basalts and oceanic plateaus because the formation mechanisms are shown to be different, Sager said.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">'Certainly One of the Largest'</span></h4> <div style="text-align: left;"> With the discovery, Sager said Tamu Massif can no longer be considered the world's largest shield volcano. That title reverts to Mauna Loa, on the island of Hawaii.<br /> <br /> "The largest volcano in the world is really the mid-ocean ridge system, which stretches about 65,000 kilometers around the world, like stitches on a baseball," Sager said. "This is really a large volcanic system, not a single volcano."<br /> <br /> Researchers now think Tamu Massif formed as part of that mid-ocean ridge system, he said. "Tamu Massif is certainly one of the largest volcanic mountains in the world."<br /> <br /> The 2013 paper was based on what researchers knew at the time, Sager said. "Science is a process and is always changing. There were aspects of that explanation that bugged me, so I proposed a new cruise and went back to collect the new magnetic data set that led to this new result.<br /> <br /> "In science, we always have to question what we think we know and to check and double check our assumptions. In the end, it is about getting as close to the truth as possible -- no matter where that leads."</div> <div style="text-align: left;"> <br /></div> <div style="text-align: left;"> <br /></div> <u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="http://www.uh.edu/news-events/stories/2019/july-2019/07092019tamu-massif.php" rel="nofollow" target="_blank">Materials</a> provided by <a href="http://www.uh.edu/" rel="nofollow" target="_blank">University of Houston</a>.</span></i></u></div>

Geoscientists Were Wrong About the 'World's Largest Volcano'

The Mauna Loa An Unexpected Discovery Just Changed The Ranking of Earth's Biggest Volcano Congratulations Mauna Loa, on the isla...

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Whole Lizard Discovered Inside 120 Million-year-old Dinosaur's Stomach

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-jIG-fnMbU7M/XSn8wRNX85I/AAAAAAAARPE/IcjPA44rIuoOFI2uRsXaWqagVHDmQZzRACLcBGAs/s1600/A%2Bnew%2Blizard%2Bspecies%2Bin%2Bthe%2Babdomen%2Bof%2Ba%2Bspecimen%2Bof%2BMicroraptor.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Whole Lizard Discovered Inside 120 Million-year-old Dinosaur's Stomach" border="0" data-original-height="909" data-original-width="1233" height="470" src="https://1.bp.blogspot.com/-jIG-fnMbU7M/XSn8wRNX85I/AAAAAAAARPE/IcjPA44rIuoOFI2uRsXaWqagVHDmQZzRACLcBGAs/s640/A%2Bnew%2Blizard%2Bspecies%2Bin%2Bthe%2Babdomen%2Bof%2Ba%2Bspecimen%2Bof%2BMicroraptor.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">A new lizard species in the abdomen of a specimen of Microraptor. Photo:Jingmai O'Connor</td></tr> </tbody></table> <br /> A new species of lizard has been discovered inside the stomach of a 120 million-year-old dinosaur. Researchers in China found the near-complete specimen inside a Microraptor zhaoianus—a small predatory dinosaur that lived during the Early Cretaceous in what is now northeastern China.<br /> <br /> A team of paleontologists led by Prof. Jingmai O'Connor from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences, together with researchers from the Shandong Tianyu Museum of Nature, have discovered a new specimen of the volant dromaeosaurid Microraptor zhaoianus with the remains of a nearly complete lizard preserved in its stomach. Their findings were published in Current Biology.<br /> <br /> The lizard is unlike any previously known from the Cretaceous and represents a new species, Indrasaurus wangi. The lizard was named after Prof. WANG Yuan from IVPP, who is also director of the Paleozoological Museum of China. Prof. WANG is an expert on the paleoherpetofauna of China and has been in charge of numerous exhibitions of Chinese fossils.<br /> <br /> The name Indrasaurus was inspired by a Vedic legend in which the god Indra was swallowed by a dragon during a great battle (the dragon here referring to Microraptor).<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> Dr. DONG Liping, a former student of Prof. WANG's, ran the most extensive phylogenetic analysis of Cretaceous lizards ever conducted and showed that all known Cretaceous species were more closely related to each other than to any modern lineage. The new lizard had teeth unlike any other previously known from the Jehol Biota, thus expanding the diversity of this clade and possibly suggesting a unique diet for this new species.<br /> <br /> This is the fourth documented occurrence of a <i>Microraptor</i> preserving stomach contents - this dinosaur is now known to have fed on mammals, birds, fish, and lizards, supporting the interpretation that it was an opportunistic predator.<br /> <br /> The lizard is nearly complete and articulated, showing that it was swallowed whole and head first, meaning that Microraptor fed in a manner similar to living carnivorous birds and lizards.<br /> <br /> Although the Jurassic troodontid Anchiornis has been recently demonstrated to have egested pellets similar to extant carnivorous birds (most famously documented in owls), this ability was apparently absent in Microraptor, further adding to the evidence that the evolutionary transition from dinosaur to bird was characterized by extreme homoplasy - that is, numerous traits evolved multiple times independently in closely related groups.<br /> <br /> Over the past 20 years, direct evidence of trophic interactions in the Jehol Biota has slowly accumulated. There are now 20 predator-prey relationships documented through direct evidence of stomach contents.<br /> <br /> The authors used these relationships to reconstruct the first Jehol food web. Although certainly preliminary, this food web indicates that fish formed the most important food source for secondary and tertiary consumers. This food web can be used in the future to better understand the Jehol ecosystem.<br /> <br /> <br /> <u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="https://linkinghub.elsevier.com/retrieve/pii/S0960982219307134" rel="nofollow" target="_blank">materials </a>provided by<a href="http://english.cas.cn/" rel="nofollow" target="_blank"> Chinese Academy of Sciences.</a></span></i></u></div>

Whole Lizard Discovered Inside 120 Million-year-old Dinosaur's Stomach

A new lizard species in the abdomen of a specimen of Microraptor. Photo:Jingmai O'Connor A new species of lizard has been discover...

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What is Crazy Lace Agate?

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-BhhnXroGLg8/XSi0KLOkE9I/AAAAAAAAROs/_Jtsh6ggRU4vzo79yg0Dk2pVO5EEJVdhQCLcBGAs/s1600/Crazy%2Blace%2Bagate%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="What is Crazy Lace Agate?" border="0" data-original-height="901" data-original-width="1200" height="480" src="https://1.bp.blogspot.com/-BhhnXroGLg8/XSi0KLOkE9I/AAAAAAAAROs/_Jtsh6ggRU4vzo79yg0Dk2pVO5EEJVdhQCLcBGAs/s640/Crazy%2Blace%2Bagate%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Crazy lace agate From Chihuahua, Mun, de Buenaventura, Sierra Santa Lucia, Ejido Benito Juarez, Mexico.<br /> Credit: Anton</td></tr> </tbody></table> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;"> </span></h4> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">Lace Agate is a variety that exhibits a lace-like pattern with forms such as eyes, swirls, bands or zigzags.</span></h4> Crazy lace agate is a banded chalcedony (microcrystalline quartz) that's infused with iron and aluminum and is often brightly colored and complexly patterned. This produces the creamy browns, blacks, greys and golds (and occasional pinks or reds) swirled together in this stone.<br /> <br /> This stone is found exclusively within the area known as Chihuahua, in Northern Mexico. Crazy lace agate is believed to have been created in the cretaceous period, about 65-90 million years ago.<br /> <br /> Agate is the most famous chalcedony variety, recognized by its concentric color bands, formed by the remains of iron and manganese. The chemical composition of agate is the same as quartz, but with a different physical structure.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> Instead of forming as large crystals, it is composed of tiny fibers and crystals whose shapes give rise to diagrams or drawings that acquire different names: as in this case "agate crazy". This mineral is formed in rock cavities of different types, especially lava.<br /> <br /> Most agates occur as nodules in volcanic rocks or ancient lavas, in former cavities produced by volatiles in the original molten mass, which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls.<br /> <br /> Agate has also been known to fill veins or cracks in volcanic or altered rock underlain by granitic intrusive masses. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section.<br /> <br /> The first deposit on the wall of a cavity, forming the "skin" of the agate, is generally a dark greenish mineral substance, like celadonite, delessite or "green earth", which are rich in iron probably derived from the decomposition of the augite in the enclosing volcanic rock.<br /> <br /> Agates can also be found in sedimentary rocks. They need a cavity to form, so they are typically seen in limestone, dolomite, and shale which may have shells, tree branches, or roots in them that later decay away.<br /> <br /> <b><span style="font-family: "georgia" , "times new roman" , serif;">See also: </span></b><br /> <span style="font-family: "georgia" , "times new roman" , serif;"><a href="http://www.geologyin.com/2016/08/types-of-agate-with-photos.html?fbclid=IwAR05Sto4HBQvh9a-Ofa-ZckHyVG1tHib7Evz6plf7GkcKmhwWCxD_BZiQjI#dSXYzAj8Byv65vzv.99" target="_blank">Types of Agate With Photos</a></span><br /> <span style="font-family: "georgia" , "times new roman" , serif;"><a href="http://www.geologyin.com/2016/04/major-varieties-of-quartz.html" target="_blank">The Major Varieties of Quartz (Photos)</a><br />  </span></div>

What is Crazy Lace Agate?

Crazy lace agate From Chihuahua, Mun, de Buenaventura, Sierra Santa Lucia, Ejido Benito Juarez, Mexico. Credit: Anton   Lace Agate ...

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Scientists Find 68-million-year-old Triceratops Fossil in Colorado

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-oiNvrPkMSzg/XSYUkinvnWI/AAAAAAAAROI/Tolo9Rj3siMt8nrHr0MpyngMLvuCLfxlgCLcBGAs/s1600/Triceratops%2Bskull%2Bfound%2Bin%2BColorado%2Bduring%2Bconstruction%2Bwork%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Scientists Find 68-million-year-old Triceratops Fossil in Colorado" border="0" data-original-height="756" data-original-width="1196" height="403" src="https://1.bp.blogspot.com/-oiNvrPkMSzg/XSYUkinvnWI/AAAAAAAAROI/Tolo9Rj3siMt8nrHr0MpyngMLvuCLfxlgCLcBGAs/s640/Triceratops%2Bskull%2Bfound%2Bin%2BColorado%2Bduring%2Bconstruction%2Bwork%2B%25281%2529.jpg" title="" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Triceratops skull found in Colorado during construction work</td></tr> </tbody></table> <div style="text-align: left;"> </div> <h4 style="text-align: left;"> <span style="font-family: Georgia, "Times New Roman", serif;">Scientists say dinosaur fossils found in Colorado are those of a 68 million years old triceratops</span></h4> Several weeks ago, construction workers digging near a Denver, Colorado, retirement home made a startling discovery: dinosaur bones.<br /><br />Paleontologists say fossilized bones unearthed at a suburban Denver construction site are those of a large adult triceratops.<br /><br />Maura O’Neal, a spokeswoman for the Denver Museum of Nature & Science, said Friday the partial skeleton included a limb bone and several ribs of the three-horned dinosaur.<br /><br />The Denver Post reports the bones were found at a construction site near a retirement community in Highlands Ranch in May in a rock layer that dates back 65 million to 68 million years.<br /><br />Construction crews are using heavy equipment to dig a deep trench in search for other dinosaur fossils next to the area where the triceratops bones were found. O’Neal says that of all the dinosaur bones discovered in Colorado, the remains of triceratops have been among the most common.<br /><br />Scientists say the possibility of unearthing more fossils runs very high. Now, the construction crews are working hand in hand with scientists to further explore the site in search of more fossil finds.<br /> <br /> <br /><br /> <i><u><span style="font-family: "Trebuchet MS", sans-serif;">The Associated Press.</span></u></i></div>

Scientists Find 68-million-year-old Triceratops Fossil in Colorado

Triceratops skull found in Colorado during construction work Scientists say dinosaur fossils found in Colorado are those of a 68 mil...

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How Solar Heat Drives Rapid Melting of Parts of Antarctica's Largest Ice Shelf

<div dir="ltr" style="text-align: left;" trbidi="on"> <table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody> <tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-DqWZdOExAT8/XSS6teoVkLI/AAAAAAAARN8/9g-P558bhZEX9mfEwRfryRpLIYJFgsOGwCLcBGAs/s1600/How%2BSolar%2BHeat%2BDrives%2BRapid%2BMelting%2Bof%2BParts%2Bof%2BAntarctica%2527s%2BLargest%2BIce%2BShelf%2B%25281%2529.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" data-original-height="607" data-original-width="1139" height="340" src="https://1.bp.blogspot.com/-DqWZdOExAT8/XSS6teoVkLI/AAAAAAAARN8/9g-P558bhZEX9mfEwRfryRpLIYJFgsOGwCLcBGAs/s640/How%2BSolar%2BHeat%2BDrives%2BRapid%2BMelting%2Bof%2BParts%2Bof%2BAntarctica%2527s%2BLargest%2BIce%2BShelf%2B%25281%2529.jpg" width="640" /></a></td></tr> <tr><td class="tr-caption" style="text-align: center;">Summer sea surface temperature surrounding Antarctica (a) and in the Ross Sea (b) showing the strong seasonal warming within the Ross Sea polynya.</td></tr> </tbody></table> <br /> <br /> <div style="text-align: left;"> The ocean that surrounds Antarctica plays a crucial role in regulating the mass balance of the continent's ice cover. We now know that the thinning of ice that affects nearly a quarter of the West Antarctic Ice Sheet is clearly linked to the ocean.<br /> <br /> The connection between the Southern Ocean and Antarctica's ice sheet lies in ice shelves—massive slabs of glacial ice, many hundreds of metres thick, that float on the ocean. Ice shelves grind against coastlines and islands and buttress the outflow of grounded ice. When the ocean erodes ice shelves from below, this buttressing action is reduced.<br /> <br /> While some ice shelves are thinning rapidly, others remain stable, and the key to understanding these differences lies within the hidden oceans beneath ice shelves. Our recently published research explores the ocean processes that drive melting of the world's largest ice shelf. It shows that a frequently overlooked process is driving rapid melting of a key part of the shelf.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">Ocean fingerprints on ice sheet melt</span></h4> <div style="text-align: left;"> Rapid ice loss from Antarctica is frequently linked to Circumpolar Deep Water (CDW). This relatively warm (+1C) and salty water mass, which is found at depths below 300 metres around Antarctica, can drive rapid melting. For example, in the south-east Pacific, along West Antarctica's Amundsen Sea coast, CDW crosses the continental shelf in deep channels and enters ice shelf cavities, driving rapid melting and thinning.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> Interestingly, not all ice shelves are melting quickly. The largest ice shelves, including the vast Ross and Filchner-Ronne ice shelves, appear close to equilibrium. They are largely isolated from CDW by the cold waters that surround them.<br /> <br /> The contrasting effects of CDW and cold shelf waters, combined with their distribution, explain much of the variability in the melting we observe around Antarctica today. But despite ongoing efforts to probe the ice shelf cavities, these hidden seas remain among the least explored parts of Earth's oceans.<br /> <br /> It is within this context that our research explores a new and hard-won dataset of oceanographic observations and melt rates from the world's largest ice shelf.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">Beneath the Ross Ice Shelf</span></h4> <div style="text-align: left;"> In 2011, we used a 260 metre deep borehole that had been melted through the north-western corner of the Ross Ice Shelf, seven kilometres from the open ocean, to deploy instruments that monitor ocean conditions and melt rates beneath the ice. The instruments remained in place for four years.<br /> <br /> The observations showed that far from being a quiet back water, conditions beneath the ice shelf are constantly changing. Water temperature, salinity and currents follow a strong seasonal cycle, which suggests that warm surface water from north of the ice front is drawn southward into the cavity during summer.<br /> <br /> Melt rates at the mooring site average 1.8 metres per year. While this rate is much lower than ice shelves impacted by warm CDW, it is ten times higher than the average rate for the Ross Ice Shelf. Strong seasonal variability in the melt rate suggests that this melting hotspot is linked to the summer inflow.<br /> <br /> To assess the scale of this effect, we used a high-precision radar to map basal melt rates across a region of about 8,000 square kilometres around the mooring site. Careful observations at around 80 sites allowed us to measure the vertical movement of the ice base and internal layers within the ice shelf over a one-year interval. We could then determine how much of the thinning was caused by basal melting.<br /> <div style="margin: 0px auto; width: 100%;"> <script async="" src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script><br /> <ins class="adsbygoogle" data-ad-client="ca-pub-1021498709184325" data-ad-format="fluid" data-ad-layout="in-article" data-ad-slot="6157425841" style="display: block; text-align: center;"></ins><br /> <script> (adsbygoogle = window.adsbygoogle || []).push({}); </script><br /></div> Melting was fastest near the ice front where we observed short-term melt rates of up to 15 centimetres per day—several orders of magnitude higher than the ice shelf average rate. Melt rates reduced with distance from the ice front, but rapid melting extended far beyond the mooring site. Melting from the survey region accounted for some 20% of the total from the entire ice shelf.</div> <h4 style="text-align: left;"> <span style="font-family: "georgia" , "times new roman" , serif;">The bigger picture</span></h4> <div style="text-align: left;"> Why is this region of the shelf melting so much more quickly than elsewhere? As is so often the case in the ocean, it appears that winds play a key role.<br /> <br /> During winter and spring, strong katabatic winds sweep across the western Ross Ice Shelf and drive sea ice from the coast. This leads to the formation of an area that is free of sea ice, a polynya, where the ocean is exposed to the atmosphere. During winter, this area of open ocean cools rapidly and sea ice grows. But during spring and summer, the dark ocean surface absorbs heat from the sun and warms, forming a warm surface pool with enough heat to drive the observed melting.<br /> <br /> Although the melt rates we observe are far lower than those seen on ice shelves influenced by CDW, the observations suggest that for the Ross Ice Shelf, surface heat is important.<br /> <br /> Given this heat is closely linked to surface climate, it is likely that the predicted reductions in sea ice within the coming century will increase basal melt rates. While the rapid melting we observed is currently balanced by ice inflow, glacier models show that this is a structurally critical region where the ice shelf is pinned against Ross Island. Any increase in melt rates could reduce buttressing from Ross Island, increasing the discharge of land-based ice, and ultimately add to sea levels.<br /> <br /> While there is still much to learn about these processes, and further surprises are certain, one thing is clear. The ocean plays a key role in the dynamics of Antarctica's ice sheet and to understand the stability of the ice sheet we must look to the ocean.</div> <div style="text-align: left;"> <br /></div> <br /> <u><i><span style="font-family: "trebuchet ms" , sans-serif;">This article is republished from The Conversation under a Creative Commons license.</span></i></u></div>

How Solar Heat Drives Rapid Melting of Parts of Antarctica's Largest Ice Shelf

Summer sea surface temperature surrounding Antarctica (a) and in the Ross Sea (b) showing the strong seasonal warming within the Ross Sea...

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