July 2019

Massive, 1,100-Pound Dinosaur Bone Unearthed in France

Massive, 1,100-Pound Dinosaur Bone Unearthed in France

Maxime Lasseron inspects the femur of a Sauropod (AFP/Getty Images) The femur of a giant dinosaur was found this week by French paleon...

Volcanoes Shaped the Climate Before Humankind

climate, Environment, volcano 7:21 PM

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<span style="font-family: "georgia" , "times new roman" , serif;">The volcanoes in the tropics went crazy between 1808 and 1835: Not only did Tambora erupt in Indonesia during this short period of time but there were also four other large eruptions. This unusual series of volcanic eruptions caused long-lasting droughts in Africa and contributed to the last advance of Alpine glaciers during the Little Ice Age.</span><br />
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"Frequent volcanic eruptions caused an actual gear shift in the global climate system," says Stefan Brönnimann, head of the international research team that discovered the effects of the series of eruptions on the oceans and thus on atmospheric circulation. Brönnimann is Professor of Climatology at the University of Bern and a member of the Oeschger Centre for Climate Research. Their research has been published in the Nature Geosciences journal.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Less rain in Africa and India, more rain and snow in Europe</span></h4>
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For their investigations, the researchers analyzed new climate reconstructions that include atmospheric circulation and compared the results to observation-based data. Model simulations finally helped to pin down the role of the oceans in climate change in the early 19th century and showed that they could not recover from the effects of the sequence of eruptions for several decades. </div>
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The consequences: the persistent weakening of the African and Indian monsoon systems and a shift of atmospheric circulation over the Atlantic-European sector. This led to an increase in low-pressure systems crossing Central Europe.<br />
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The last glacier advance in the Alps from the 1820s to the 1850s, depicted in paintings and even old photographs, is a consequence of increased precipitation due to the altered circulation in combination with low temperatures. However, global temperature increased again from the late 19th century onward. The Little Ice Age was eventually superseded by a first phase of global warming, culminating in the 1940s and with a significant humanmade contribution.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Important for the definition of "pre-industrial climate"</span></h4>
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The new Bern study not only explains the global early 19th century climate, but it is also relevant for the present. "Given the large climatic changes seen in the early 19th century, it is difficult to define a pre-industrial climate," explains lead author Stefan Brönnimann, "a notion to which all our climate targets refer." And this has consequences for the climate targets set by policymakers, who want to limit global temperature increases to between 1.5 and 2 degrees Celsius at the most. Depending on the reference period, the climate has already warmed up much more significantly than assumed in climate discussions. </div>
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The reason: Today's climate is usually compared with a 1850-1900 reference period to quantify current warming. Seen in this light, the average global temperature has increased by 1 degree. "1850 to 1900 is certainly a good choice but compared to the first half of the 19th century, when it was significantly cooler due to frequent volcanic eruptions, the temperature increase is already around 1.2 degrees," Stefan Brönnimann points out.<br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="https://www.unibe.ch/news/media_news/media_relations_e/media_releases/2019/medienmitteilungen_2019/volcanoes_shaped_the_climate_before_humankind/index_eng.html" rel="nofollow" target="_blank">Materials</a> provided by <a href="http://www.unibe.ch/" rel="nofollow" target="_blank">University of Bern</a>.</span></i></u></div>

Volcanoes Shaped the Climate Before Humankind

The volcanoes in the tropics went crazy between 1808 and 1835: Not only did Tambora erupt in Indonesia during this short period of tim...

Mysterious Glass Beads in Clams Point to Ancient Meteorite Strike Near Florida

Meteorite, Researches 6:46 PM

Mysterious Glass Beads in Clams Point to Ancient Meteorite Strike Near Florida

A pair of microtektites found inside ancient clam shells. Image: Kristen Grace, Florida Museum Glass beads were found inside fossil cl...

The Earth’s Core is Leaking, Baffling Scientists

earth, Earth's magnetic field, Geology 6:58 PM

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<tr><td class="tr-caption" style="text-align: center;">How the Earth's core might be leaking material into the mantle plumes. (Photo: Neil Bennett)</td></tr>
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<span style="font-family: "georgia" , "times new roman" , serif;">Earth’s Leaking Core Could Cause Planet’s Magnetic Field To Collapse</span><br />
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<span style="font-family: "georgia" , "times new roman" , serif;">Earth's magnetic field protects and makes our planet habitable by stopping harmful high-energy particles from space, including from the Sun. The source of this magnetic field is the core at the centre of our planet.</span><br />
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But the core is very difficult to study, partly because it starts at a depth of about 2,900 kilometres (1,800 miles), making it too deep to sample and directly investigate.<br />
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Yet we are part of a research team that found a way to get information about Earth's core, with details published recently in Geochemical Perspective Letters.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">It's hot down there</span></h4>
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The core is the hottest part of our planet with the outer core reaching temperatures of more than 5,000 degrees Celsius (9,000 Fahrenheit). This has to affect the overlying mantle and it is estimated that 50 percent of volcanic heat comes from the core.<br />
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Volcanic activity is the planet's main cooling mechanism. Certain volcanism, such as that which is still forming volcanic islands of Hawaii and Iceland, might be linked to the core by mantle plumes that transfer heat from the core to Earth's surface.<br />
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Yet whether there is any exchange of physical material between the core and the mantle has been a subject of debate for decades.<br />
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Our findings suggest some core material does transfer into the base of these mantle plumes, and the core has been leaking this material for the past 2.5 billion years.<br />
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We discovered this by looking at very small variations in the ratio of isotopes of the element tungsten (isotopes are basically versions of the same element that just contain different numbers of neutrons).<br />
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To study Earth's core, we need to search for chemical tracers of core material in volcanic rocks derived from the deep mantle.<br />
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We know the core has a very distinct chemistry, dominated by iron and nickel together with elements such as tungsten, platinum and gold that dissolve in iron-nickel alloy. Therefore, the metal alloy-loving elements are a good choice to investigate for traces of the core.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">The search for tungsten isotopes</span></h4>
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Tungsten (chemical symbol W) as the base element has 74 protons. Tungsten has several isotopes, including <sup>182</sup>W (with 108 neutrons) and <sup>184</sup>W (with 110 neutrons).<br />
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These isotopes of tungsten have potential to be the most conclusive tracers of core material, because the mantle is expected to have much higher <sup>182</sup>W/<sup>184</sup>W ratios than the core.<br />
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This is because of another element, Hafnium (Hf), which does not dissolve in iron-nickel alloy and is enriched in the mantle, and had a now-extinct isotope (182Hf) that decayed to <sup>182</sup>W. This gives the mantle extra <sup>182</sup>W relative to the tungsten in the core.<br />
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But the analysis required to detect variations in tungsten isotopes is incredibly challenging, as we are looking at variations in the <sup>182</sup>W/<sup>184</sup>W ratio in parts per million and the concentration of tungsten in rocks is as low as tens of parts per billion. Fewer than five laboratories in the world can do this type of analysis.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Evidence of a leak</span></h4>
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Our study shows a substantial change in the <sup>182</sup>W/<sup>184</sup>W ratio of the mantle over Earth's lifetime. Earth's oldest rocks have significantly higher <sup>182</sup>W/<sup>184</sup>W than than most rocks of the modern-day Earth.<br />
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The change in the <sup>182</sup>W/<sup>184</sup>W ratio of the mantle indicates that tungsten from the core has been leaking into the mantle for a long time.<br />
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Interestingly, in Earth's oldest volcanic rocks, over a time frame of 1.8 billion years there is no significant change in the mantle's tungsten isotopes. This indicates that from 4.3 billion to 2.7 billion years ago, little or no material from the core was transferred into the upper mantle.<br />
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But in the subsequent 2.5 billion years, the tungsten isotope composition of the mantle has significantly changed. We infer that a change in plate tectonics, towards the end of the Archean Eon from about 2.6 billion years ago triggered large enough convective currents in the mantle to change the tungsten isotopes of all modern rocks.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Why the leak?</span></h4>
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If mantle plumes are ascending from the core-mantle boundary to the surface, it follows that material from Earth's surface must also descend into the deep mantle.<br />
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Subduction, the term used for rocks from Earth's surface descending into the mantle, takes oxygen-rich material from the surface into the deep mantle as an integral component of plate tectonics.<br />
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Experiments show that increase in oxygen concentration at the core-mantle boundary could cause tungsten to separate out of the core and into the mantle.<br />
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Alternatively, inner core solidification would also increase the oxygen concentration of the outer core. In this case, our new results could tell us something about the evolution of the core, including the origin of Earth's magnetic field.<br />
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Earth's core started as entirely liquid metal and has been cooling and partially solidifying over time. The magnetic field is generated by the spin of the inner solid core. The time of inner core crystallisation is one of the most difficult questions to answer in Earth and planetary sciences.<br />
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Our study gives us a tracer that can be used to investigate core-mantle interaction and the change in the internal dynamics of our planet, and which can boost our understanding of how and when the magnetic field was turned on.<br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">This article is republished from <a href="https://theconversation.com/" rel="nofollow" target="_blank">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/earths-core-has-been-leaking-for-billions-of-years-119395" rel="nofollow" target="_blank">original article</a>.</span></i></u></div>
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The Earth’s Core is Leaking, Baffling Scientists

How the Earth's core might be leaking material into the mantle plumes. (Photo: Neil Bennett) Earth’s Leaking Core Could Cause Pl...

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

Earth History, volcano 7:25 PM

'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,...

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

Earthquakes, News 7:03 PM

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, ...

What Delayed Earth’s Oxygenation?

earth, Earth History 7:43 PM

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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 />
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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 />
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“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 />
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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 />
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</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 />
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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 />
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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 />
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“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 />
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<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...

Ringing Rocks A Geological and Musical Marvel

Geology, places to visit, Rocks, USA 7:17 PM

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<tr><td class="tr-caption" style="text-align: center;">Ringing Hill Park. Photo: Sherry M/TripAdvisor</td></tr>
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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 />
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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 />
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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 />
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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 />
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<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 />
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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 />
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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 />
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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 />
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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 />
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<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 />
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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 />
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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 />
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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 />
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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 />
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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> <span style="color: blue;"><b><span style="font-family: "georgia" , "times new roman" , serif;">Video:</span></b></span><br />
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<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 />
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<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 ha...

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

Geology, Researches, volcano 6:49 PM

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<tr><td class="tr-caption" style="text-align: center;">The Mauna Loa </td></tr>
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<span style="font-family: "georgia" , "times new roman" , serif;">An Unexpected Discovery Just Changed The Ranking of Earth's Biggest Volcano</span><br />
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<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 />
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<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 />
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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 />
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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 />
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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 />
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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>
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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 />
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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 />
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"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>
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<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

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

What is Crazy Lace Agate?

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What is Crazy Lace Agate?

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

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

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

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

Antarctic, climate, Researches 7:04 PM

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<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>
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<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 />
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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 />
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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 />
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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 />
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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>
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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 />
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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 />
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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 />
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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 />
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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 />
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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 />
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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 />
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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 />
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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>
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<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...

Mystery of Bizarre Salt Crystals in The Dead Sea Could Finally Be Solved

earth, Geology, Researches 5:55 PM

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<tr><td style="text-align: center;"><a href="https://1.bp.blogspot.com/-IWHLJojtlK8/XSSpmFC4YmI/AAAAAAAARNw/yHx3Gz10f9cVvFkXuYQHjAuuzT34rhuFQCLcBGAs/s1600/Mystery%2Bof%2BBizarre%2BSalt%2BCrystals%2Bin%2BThe%2BDead%2BSea%2BCould%2BFinally%2BBe%2BSolved.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img alt="Mystery of Bizarre Salt Crystals in The Dead Sea Could Finally Be Solved" border="0" data-original-height="828" data-original-width="1199" height="440" src="https://1.bp.blogspot.com/-IWHLJojtlK8/XSSpmFC4YmI/AAAAAAAARNw/yHx3Gz10f9cVvFkXuYQHjAuuzT34rhuFQCLcBGAs/s640/Mystery%2Bof%2BBizarre%2BSalt%2BCrystals%2Bin%2BThe%2BDead%2BSea%2BCould%2BFinally%2BBe%2BSolved.jpg" title="" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Salt Formations at the Dead Sea. Photo: VoteDeadSea.</td></tr>
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<span style="font-family: "georgia" , "times new roman" , serif;">New research explains why salt crystals are piling up on the deepest parts of the Dead Sea's floor, a finding that could help scientists understand how large salt deposits formed in Earth's geologic past.</span><br />
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The Dead Sea, a salt lake bordered by Jordan, Israel and the West Bank, is nearly 10 times as salty as the ocean. Humans have visited the Dead Sea for thousands of years to experience its purported healing properties and to float in its extremely dense, buoyant waters, and mention of the sea goes back to biblical times.<br />
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Much of the freshwater feeding the Dead Sea has been diverted in recent decades, lowering the sea's water levels and making it saltier than before. Scientists first noticed in 1979, after this process had started, that salt crystals were precipitating out of the top layer of water, "snowing" down and piling up on the lakebed. The salt layer on the lake floor has been growing about 10 centimeters (4 inches) thicker every year.<br />
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The process driving this salt crystal "snow" and buildup of salt layers on the lakebed has puzzled scientists because it doesn't make sense according to the laws of physics. Now, a new study in AGU's journal Water Resources Research proposes that tiny disturbances in the lake, caused by waves or other motion, create "salt fingers" that slowly funnel salt down to the lakebed.<br />
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"Initially you form these tiny fingers that are too small to observe... but quickly they interact with each other as they move down, and form larger and larger structures," said Raphael Ouillon, a mechanical engineer at the University of California Santa Barbara and lead author of the new study.<br />
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"The initial fingers might only be a few millimeters or a couple of centimeters thick, but they're everywhere across the entire surface of the lake," said Eckart Meiburg, also a mechanical engineer at UC Santa Barbara and co-author of the new study. "Together these small fingers generate a tremendous amount of salt flux."<br />
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The new finding helps researchers better understand the physics of the Dead Sea but also helps explain the formation of massive salt deposits found within Earth's crust.<br />
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The Dead Sea is only hypersaline water body on Earth today where this salt fingering process is happening, so it represents a unique laboratory for researchers to study the mechanisms by which these thick salt deposits have formed, according to the authors.<br />
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"Altogether this makes the Dead Sea a unique system," said Nadav Lensky, a geologist with the Geological Survey of Israel and co-author of the new study. "Basically, we have here a new finding that we think is very relevant to the understanding of the arrangement of these basins that were so common in Earth's history."</div>
<h4 style="text-align: left;">
<span style="font-family: "georgia" , "times new roman" , serif;">A salty mystery</span></h4>
<div style="text-align: left;">
As the Dead Sea has become saltier in recent decades, much of that salt has become concentrated near its surface. During the summer, extra heat from the Sun warms the surface of the Dead Sea and divides it into two distinct layers: A warm top layer sitting atop a colder lower layer. As water evaporates from the top layer in the summer heat, it becomes saltier than the cooler layer below.<br />
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Researchers realized the salt snow they observed was originating in this top salty layer, but this warm water doesn't mix with the cooler water below because it's so much warmer and less dense. So they were puzzled as to how salt from the surface was entering the cooler layer and plummeting to the bottom of the lake.<br />
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Lensky and his colleagues proposed an explanation in 2016, and the new research tests this theory for the first time.<br />
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They propose that when the top layer of the lake is disturbed by waves or other motion, tiny parcels of warm water enter the cooler pool of water below. Heat diffuses more rapidly than salt, so this warm water parcel rapidly cools. But as it cools it holds less salt, so the salt precipitates out and forms crystals that sink to the bottom. Watch an animation of the salt fingers here.<br />
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In the new study, researchers created a computer simulation of how water and salt would flow in the Dead Sea if the salt fingers theory was correct. They found the salt fingers theory correctly predicted the downward flow of salt snow and buildup of salt layers in the middle of the lake's floor. Because the level of the lake is declining, due to pumping of freshwater from the nearby Jordan River, the salt layers are concentrated in the central part of the lake, according to the authors.</div>
<h4 style="text-align: left;">
<span style="font-family: "georgia" , "times new roman" , serif;">Understanding salt deposits elsewhere</span></h4>
<div style="text-align: left;">
The new finding also helps explain the formation of massive salt deposits found within Earth's crust.<br />
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"We know that many places around the world have thick salt deposits in the Earth's crust, and these deposits can be up to a kilometer thick," Meiburg said. "But we're uncertain how these salt deposits were generated throughout geological history."<br />
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One notable example is the thick salt layer underneath the Mediterranean Sea. Researchers know that about six million years ago, the Strait of Gibraltar closed off, because of the movements of Earth's tectonic plates. This cut off the supply of water from the Atlantic Ocean to the Mediterranean, creating a giant shallow inland sea.<br />
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After several hundred thousand years, the Mediterranean's water levels dropped so much that the sea partly or nearly dried out, leaving behind thick deposits of salt. The new finding suggests these deposits formed during this time in a similar manner to what is happening right now in the Dead Sea. When the Strait of Gibraltar opened up again, water flooded the basin and the salt deposits were buried under new layers of sediment, where they remain today.</div>
<div style="text-align: left;">
<br /></div>
<br />
<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above story is based on <a href="https://news.agu.org/press-release/new-study-solves-mystery-of-salt-buildup-on-bottom-of-dead-sea/" rel="nofollow" target="_blank">Materials</a> provided by <a href="http://www.agu.org/" rel="nofollow" target="_blank">American Geophysical Union</a>.</span></i></u></div>

Mystery of Bizarre Salt Crystals in The Dead Sea Could Finally Be Solved

Salt Formations at the Dead Sea. Photo: VoteDeadSea. New research explains why salt crystals are piling up on the deepest parts of th...

Will the Southern California Earthquakes Cause Yellowstone to Erupt?

earth, USA, Yellowstone 6:30 PM

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With the two strong earthquakes in southern California these past few days—a M6.4 on July 4 and a M7.1 a day later—it's a natural question: Will these earthquakes trigger volcanic eruptions? Including perhaps at Yellowstone? There was apparently a spike in Internet searches on this very question, so we thought it would be a good idea to address it up front in this week's edition of Yellowstone Caldera Chronicles.<br />
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If you want the short version of the story, here it is: Earthquakes like those of the past week are unlikely to trigger volcanic eruptions, although they might trigger microearthquakes at some volcanoes.<br />
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Now for the long version of the story. Let's start with some historical perspective. M6-7 earthquakes are, unfortunately, pretty common occurrences in the western United States. Since 1900, in the continental USA there have nearly 100 earthquakes greater than M6, and there have been 9 greater than M7 (both of these numbers go up if you include Canada and Mexico). Most of these events are in California, but they have also occurred in Oregon, Washington, Nevada, Utah, Idaho, Montana, and Wyoming. If we assume that rate is representative of the average, that means there would be about 10 M7+ events per century in the western USA.<br />
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Yellowstone has not erupted in 70,000 years, and that was a lava flow, not an explosive eruption. That means there might have been something like 7000 M7+ earthquakes in that time period. None caused Yellowstone to erupt.<br />
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Using a simple dose of common sense, we can see this is the case just from recent history. In 1992, there was a M7.3 quake—the Landers earthquake—about 25 miles (40 km) north of Palm Springs in southern California. And in 1999, there was an M7.1 event—the Hector Mine earthquake—about 55 miles (90 km) north of Palm Springs. Neither of these caused an eruption, in Yellowstone or anywhere elsewhere—not at Coso (in California, near Ridgecrest, the site of the recent strong earthquakes), not at Long Valley caldera (in eastern California, near Mammoth), and so forth.<br />
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Proximity to Yellowstone doesn't matter. In 1959, the M7.3 Hebgen Lake earthquake occurred right on the Montana-Idaho border, essentially on the western boundary of Yellowstone National Park. And of course, there was no eruption.<br />
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But it's not as if strong earthquakes don't have any impact at all on the volcanoes of the United States. They sometimes do. Just not in ways that are obvious.<br />
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For example, both the 1992 Landers and 1999 Hector Mine earthquakes in southern California triggered some seismicity—mostly M1 or less—at Long Valley caldera. Perhaps even more amazingly, the 2002 M7.9 Denali earthquake, in Alaska, triggered small earthquakes at many mainland US volcanoes—Mount Rainier, Coso, Long Valley caldera, and even Yellowstone!<br />
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You might ask, how do we know that the smaller quakes are triggered by the larger quake? Good question! Based on seismic data, we can see that these smaller quakes start at the same time as the waves from the distant large earthquake arrive. Some of these triggered swarms have lasted for days.<br />
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The next logical question is: What do these triggered quakes mean? There are a few possible explanations. It might be that the seismic waves from the distant strong earthquake cause water and gas—fluids that might come from magma reservoirs—to move around beneath the ground. As the fluids move in the subsurface, they cause rock to break. Presto! Small earthquakes! Another possibility is that passing seismic waves cause small increases in fluid pressure. Since hydrothermal systems are already at a critical pressure (which is why there are geysers), any small increase can cause microfractures, and thus small earthquakes. Probably both possibilities are true, and act in different ways at different volcanoes.<br />
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Large earthquakes can also cause changes in hydrothermal systems, like Yellowstone's geysers. The 1959 Hebgen Lake earthquake was the most striking in this regard. Within a day of that earthquake, at least 289 springs in Yellowstone had erupted as geysers, and 160 of these were springs with no previous record of eruption! Even after the 2002 Denali, Alaska, earthquake, some geysers changed their patterns, erupting more, or less, frequently. But not every geyser was affected—some, like Old Faithful, did not seem to feel the earthquake at all. This fickle response is a testament to the fragile nature of geyser plumbing systems.<br />
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So strong earthquakes can indeed have an impact on volcanoes. But triggering eruptions? That's not common, especially in the mainland USA, where hundreds of M7+ events have clearly had no impact on volcanoes like Yellowstone, Long Valley, Coso, and elsewhere.<br />
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<span style="font-family: Georgia, "Times New Roman", serif;">See also:</span><br />
<span style="font-family: Georgia, "Times New Roman", serif;"><a href="https://www.geologyin.com/2014/11/study-yellowstone-magma-much-bigger.html" target="_blank">Study: Yellowstone Magma Much Bigger Than Thought</a></span><br />
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above post is reprinted from <a href="https://volcanoes.usgs.gov/volcanoes/yellowstone/article_home.html?utm_source=twitter&utm_medium=social&utm_term=56bb122d-05ce-4a6b-9bd3-19cf8fc2f841&utm_content=&utm_campaign=" rel="nofollow" target="_blank">Materials </a>provided by USGS.</span></i></u></div>

Will the Southern California Earthquakes Cause Yellowstone to Erupt?

With the two strong earthquakes in southern California these past few days—a M6.4 on July 4 and a M7.1 a day later—it's a natural q...

What Caused California’s Two Big Earthquakes?

Earthquakes, Geology, USA 7:14 PM

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<tr><td class="tr-caption" style="text-align: center;">A fissure that opened in the desert during the powerful earthquake. Photo:David McNew/Reuters<br />
Map of California fault line.</td></tr>
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On the morning of July 4, a magnitude 6.4 rocked Southern California, fracturing roads and sending people fleeing to safety. But that wasn’t all the Earth had in store: Less than a day and a half later, a powerful magnitude 7.1 temblor shook the region.<br />
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While earthquakes are not unexpected, the two most recent temblors are the largest that have struck this area in decades. And they promise to yield fresh clues about its complex geology.<br />
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The duo of quakes struck in what’s known as the Eastern California shear zone—an area east of the infamous San Andreas fault, where the Pacific Plate grinds against the North American Plate, creeping northwest at roughly two inches each year. The area extends from the southern Mojave Desert, up the eastern side of the Sierra Nevada, and into western Nevada. It’s crisscrossed by fractures in the Earth caused by the movement along the nearby tectonic plate boundary.<br />
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“The Eastern California shear zone is a really interesting area,” says Wendy Bohon, an earthquake geologist at the Incorporated Research Institutions for Seismology (IRIS). “How is it working? How is it accommodating plate motion? What are going to be the big structures that come out of this millions of years down the road?”</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">What happened?</span></h4>
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The recent events are what’s known as strike-slip earthquakes, which occur when two blocks of Earth shift side-by-side, grinding past each other. They seemed to have occurred along the same set of faults, located in an area known as the Little Lake fault zone.<br />
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While no deaths or major injuries have yet been reported, the intensity of the ground movement was quite strong—enough to send goods flying off store shelves and buildings swaying. The shaking was also widespread, with reports of light ground movements as far as Chico, California, and Phoenix, Arizona.<br />
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Of particular interest in these quakes is that at least the first temblor seemed to have simultaneously broken two sections of faults that cut across each other at nearly a right angle. While such complex quakes are not unheard of, recent research suggests that they may be more common than once believed, explains Zachary Ross, a geophysicist at the California Institute of Technology.<br />
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“Historically, the thought has been that earthquakes occurred on individual faults,” he says. “And then over time, as the data has gotten better and better, we’ve started to realize that there’s potential for multiple faults to rupture for single events.”<br />
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This shift in thinking was propelled by the magnitude 7.3 earthquake that shook Landers, California, in 1992. This temblor fractured along at least five fault segments. Subsequent earthquakes have revealed similar complex breakage, including the magnitude 7.2 earthquake in 2010 in Baja California, Ross notes. This latest quake is further evidence that this complexity is common, even for smaller magnitude events.</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">Why did two big earthquakes strike?</span></h4>
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In most circumstances, big earthquakes strike in a familiar sequence: There’s a large earthquake followed by a series of smaller events. That’s because the movement that occurs during a large earthquake causes increased strain in the surrounding region. Earthquakes are the Earth’s way of relieving this strain.<br />
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But in some circumstances, such as the recent pair of earthquakes in California, a relatively large temblor might just be the forerunner for even bigger event. While the difference between 7.1 and 6.4 may seem minor, magnitude is a logarithmic scale. An increase of a unit of magnitude is about 32 times more energy, which means that the second earthquake released roughly 11 times the energy of the first temblor.<br />
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Scientists think of this series of earthquakes as the foreshock, the mainshock or strongest event, and then the aftershocks, explains Susan Hough, a seismologist with the U.S. Geological Survey.<br />
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But it’s way too simplistic,” she notes.<br />
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Every earthquake causes a shift in the landscape, redistributing the strain in the crust, which means all earthquakes could trigger other earthquakes. “Whether or not an earthquake itself is an aftershock,” she says, “you can think of it as a potential [earthquake] parent.”<br />
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The likelihood that a big earthquake will trigger a larger event is roughly one in 20, according to Hough. That’s definitely a low risk. “But that one in 20 isn’t zero,” she says.<br />
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Scientists, however, are still untangling the connection between the recent events. The magnitude 7.1 temblor seemed to break along the the northwest-southeast limb of the pair of faults that ruptured earlier, Hough notes, extending farther than the first quake in both directions.<br />
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“Major scientific questions: Did part of the fault break and then break again? How did breaks compare in detail?” she writes on Twitter. Finding the answers to these questions could have important implications for understanding the hazards of these events.<br />
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“This appears to be the clearest case I've seen that that did indeed happen,” she says of the same fault rupturing more than once in a short time period. “But much work is needed to sort out the details.”</div>
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<span style="font-family: "georgia" , "times new roman" , serif;">What’s going to happen next?</span></h4>
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So far, many more than a thousand aftershocks have rippled through the region. While the frequency and intensity of subsequent temblors will wane, Southern California likely has more shaking in store. “A magnitude 7 is going to produce activity for years,” Ross says.<br />
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The USGS estimates that over the course of the next week, between 240 and 410 earthquakes of magnitude 3 or higher will likely ripple through the region. These are events just large enough to feel if you are positioned close to their epicenter. As for larger earthquakes, the probability becomes increasingly small, but not out of the question.<br />
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The USGS estimates that there’s a 24 percent chance that as many as two earthquakes magnitude 6 or larger could strike in the next week. But as scientists continue to analyze these events, they may adjust those numbers.<br />
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Such a strong series of aftershocks is not unexpected. “Earthquakes out in the Mojave Desert traditionally have these bigger, robust aftershocks sequence,” Bohon says.<br />
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She cautions, however, that all of these probabilities are forecasts and not predictions. No one, despite what some claim, can predict future earthquakes. She likens the difference to weather forecasts, which are an estimate of the probability that something might happen.<br />
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“You would never predict the weather,” she says. “You can’t predict with 100 percent certainty that it [will be] raining unless it’s raining. And earthquakes are very similar.“<br />
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Bohon emphasizes that it’s normal to be scared during an earthquake, which can rock the ground like a boat in rough water. But as aftershocks ricochet through Southern California, she suggests people who live in earthquake-prone regions check how prepared they are for the next event.<br />
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“This was a good scenario earthquake,” says Bohon. “It was in a fairly unpopulated area, but a lot of people felt it.” Bohon hopes that means those who experienced it are getting ready for the next one.<br />
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“It’s okay to be scared,” she says, “but we also have to be prepared.”</div>
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<u><i><span style="font-family: "trebuchet ms" , sans-serif;">The above post is reprinted from<a href="https://www.nationalgeographic.com/science/2019/07/science-behind-californias-two-big-earthquakes/" rel="nofollow" target="_blank"> National Geographic.</a></span></i></u></div>
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What Caused California’s Two Big Earthquakes?

A fissure that opened in the desert during the powerful earthquake. Photo:David McNew/Reuters Map of California fault line. On the m...

Geology In