Keyword: platetectonics
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Geoscientists in Scotland say they have evidence to disprove the controversial "Snowball Earth" theory - the idea that the planet was completely encased in ice just over 600 million years ago.We are claiming that in reality there was not a totally frozen snowball Earth and that even during the coldest conditions large regions remained ice-free -- Dr Dan CondonThe team, from the University of St Andrews, has published its findings in the scientific journal Geology, after studying rocks in the west of Scotland, Ireland, Namibia and California. Drs Dan Condon, Tony Prave and Doug Benn say they have found evidence...
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Five times in the last half a billion years, tremendous, global-scale extinctions have wiped out a significant fraction of life on Earth - and each of them presents a grand puzzle. The most recent and the most familiar is the extinction that wiped out the dinosaurs - between the Cretaceous and Tertiary periods, about 65 million years ago. But before that, 205 million years ago, was the "End-Triassic Event" - it set the stage for the Jurassic Period, which saw the rise to prominence of the dinosaurs. Just what happened that killed off half the species on the planet, though,...
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A team from Harvard University presented a study this month that remnants from an ancient Earth exists, right now, inside contemporary Earth. The group believes that their comparisons of isotopic ratios of noble gases from materials deep inside Earth with those near the surface provide testimony that the deep-down material is actually from the Earth that existed before its massive collision with another planet. That immense impact – the largest in geologic history – is what many believe led to creation of the Moon. The currently favored theory about how the Moon originated says that it was formed 4.5 billion...
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WASHINGTON (AFP) - A meteor's roaring crash into Antarctica -- larger and earlier than the impact that killed the dinosaurs -- caused the biggest mass extinction in Earth's history and likely spawned the Australian continent, scientists said. Ohio State University scientists said the 483-kilometer-wide (300-mile-wide) crater is now hidden more than 1.6 kilometers (one mile) beneath the East Antarctic Ice Sheet. "Gravity measurements that reveal its existence suggest that it could date back about 250 million years -- the time of the Permian-Triassic extinction, when almost all animal life on Earth died out," the university said in a statement Thursday....
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A dinosaur bone discovered in Australia has defied prevailing wisdom about how the world's continents separated from a super-continent millions of years ago, a new study said. The 19-centimetre bone was found in southeastern Australia but it comes from a very close cousin to Megaraptor, a flesh-ripping monster that lorded over swathes of South American some 90 million years ago. The extraordinary similarity between the two giant theropods adds weight to a dissident view about the break-up of a super-continent, known as Gondwana, that formed the continents of the southern hemisphere, the authors said on Tuesday. Gondwana broke up during...
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A snapshot of New Zealand's climate 40 million years ago reveals a greenhouse Earth, with warmer seas and little or no ice in Antarctica, according to research recently published in the journal Geology. The study suggests that Antarctica at that time was yet to develop extensive ice sheets. Back then, New Zealand was about 1100 km further south, at the same latitude as the southern tip of South America -- so was closer to Antarctica -- but the researchers found that the water temperature was 23-25°C at the sea surface and 11-13°C at the bottom. "This is too warm to...
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THE world's sea levels fell in 2011 and it's all Australia's doing. New US research shows Australia's dry soil and mountainous coastline soaked up heavy rainfall in 2010 and 2011 and stopped it from flowing back into the ocean. That effectively halted a longterm trend of rising sea levels which have been caused by higher temperatures and melting ice sheets. "No other continent has this combination of atmospheric set-up and topography," scientist John Fasullo, who worked on the study, said in a statement. "Only in Australia could the atmosphere carry such heavy tropical rains to such a large area, only...
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A large fragment of an asteroid that punched 160km-wide (100 miles) hole in the Earth's surface has been found. The beachball-sized fossil meteorite was dug out of the 145-million-year-old Morokweng crater in South Africa. It is a unique discovery because large objects are widely believed to completely melt or vaporise as they collide with the planet. Writing in the journal Nature, an international team says the find will further knowledge on asteroid impacts. The Morokweng crater is one of the largest on Earth, and was formed at the boundary of the Jurassic and Cretaceous periods. Created by an asteroid...
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Scientists drilling deep into the edge of modern Antarctica have pulled up proof that palm trees once grew there. Analyses of pollen and spores and the remains of tiny creatures have given a climatic picture of the early Eocene period, about 53 million years ago. The study in Nature suggests Antarctic winter temperatures exceeded 10C, while summers may have reached 25C. Better knowledge of past "greenhouse" conditions will enhance guesses about the effects of increasing CO2 today. The early Eocene - often referred to as the Eocene greenhouse - has been a subject of increasing interest in recent years as...
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The ancient sea floor was discovered in southwest Greenland A sliver of four-billion-year-old sea floor has offered a glimpse into the inner workings of an adolescent Earth.The baked and twisted rocks, now part of Greenland, show the earliest evidence of plate tectonics, colossal movements of the planet's outer shell. Until now, researchers were unable to say when the process, which explains how oceans and continents form, began. The unique find, described in the journal Science, shows the movements started soon after the planet formed. "Since the plate tectonic paradigm is the framework in which we interpret all modern-day geology,...
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Researchers at Monash University and Scripps Institution of Oceanography identify movements of plate and plate boundaries; could substantially improve models of tectonic motionScripps Institution of Oceanography / University of California, San DiegoA team of researchers including Scripps Institution of Oceanography, UC San Diego geophysicist Dave Stegman has developed a new theory to explain the global motions of tectonic plates on the earth's surface. The new theory extends the theory of plate tectonics - a kinematic description of plate motion without reference to the forces behind it - with a dynamical theory that provides a physical explanation for both the motions...
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The Pacific is the biggest ocean on Earth, but it's getting smaller every day. Australasia and the Americas are inching closer together, and in about 350 million years the Pacific will effectively close. That's when plate tectonics - the process driving all that slow motion, and one that geologists have assumed to be continuous - may grind to a halt.
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WASHINGTON (AFP) - A first-ever high-resolution map of Mars' entire magnetic field provides new evidence that Earth-like plate tectonics - great crustal plates pulling apart and crashing together - underpin the Red Planet's surface geology, US space agency NASA said. Using the map made by the National Aeronautic and Space Administration's Mars Global Surveyor spacecraft, scientists were able to detect signs of transform faults, which are tell-tale indications of plate tectonics on Earth. The results of the scientists' research appeared in the October 10 edition of the journal Proceedings of the National Academy of Sciences. Evidence of plate tectonics at...
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A new study suggests that two recent earthquakes may indicate a literal seismic shift in our understanding of tectonic plate movements. Massive earthquakes under the Indian Ocean that took place last spring are the largest of their kind ever recorded. The 8.7 magnitude quake, followed by a 8.2 magnitude aftershock, could signal the formation of a new plate boundary under the Earth. While not the largest earthquakes ever recorded, the two quakes are notable for their unusual location. The majority of earthquakes are known as thrust faults: massive sheets of rock sliding over or under another block along a fault...
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SYDNEY (Reuters) - The island continent of Australia was once three continents which collided 1.64 billion years ago, a new study has found, prompting speculation of new mineral deposits in the outback. "Northern, western and central Australia all belonged to different continents," said Kate Selway, author of the study. "If you looked south from Alice Springs (in central Australia) before 1.64 billion years ago, you would have seen an ocean," Selway said in a statement on Thursday. "The huge forces involved in this collision produced volcanoes which actually helped create the crust of central Australia," she said. Selway, a PhD...
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Colored polygons represent different geological units that have been mapped (and inferred) by geologists over many years. These geological units formed before the continents broke apart, so we can use their position to put the "jigsaw pieces" back together again. Many other reconstructions do not use the geological boundaries to match the continental "jigsaw pieces" back together - so they don't align properly. Courtesy of University of Royal Holloway London A new study published in the journal Gondwana Research, has revealed the past position of the Australian, Antarctic and Indian tectonic plates, demonstrating how they formed the supercontinent Gondwana 165...
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For about 60 million years during the Eocene epoch, the Indian subcontinent was a huge island. Having broken off from the ancient continent of Gondwanaland, the Indian Tectonic Plate drifted toward Eurasia. During that gradual voyage, the subcontinent saw a blossoming of exceptional wildlife, and when the trove of unique biodiversity finally made contact with bigger Eurasia, the exchange of animals and plants between these areas laid the foundations for countless modern species. "Today, mainland Asia and India have all this unique biodiversity -- but did the mainland Asian biodiversity come from India, or did the Indian biodiversity come from...
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Earth has some special features that set it apart from its close cousins in the solar system, including large oceans of liquid water and a rich atmosphere with just the right ingredients to support life as we know it. Earth is also the only planet that has an active outer layer made of large tectonic plates that grind together and dip beneath each other, giving rise to mountains, volcanoes, earthquakes and large continents of land. Geologists have long debated when these processes, collectively known as plate tectonics, first got underway. Some scientists propose that the process began as early as...
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In our planet's early history, 720 to 640 million years ago, thick sheets of ice covered the majority of the surface, as the Earth was locked in a deep freeze. But explosive underwater volcanoes changed the chemistry of the Earth's oceans and were key to breaking the planet from its icy state, according to a new study. Researchers at the University of Southampton believe underwater volcanoes helped to thaw out "Snowball Earth", and even led to runaway chemical chain reactions, which created the conditions for an explosion of life on Earth. While much of the driving forces behind glaciation during...
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Since 2010, the best estimate of the age of Earth's magnetic field has been 3.45 billion years. But now a researcher responsible for that finding has new data showing the magnetic field is far older. John Tarduno, a geophysicist at the University of Rochester and a leading expert on Earth's magnetic field, and his team of researchers say they believe the Earth's magnetic field is at least four billion years old.
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