Topic
Scientific theory that Earth's crust is divided into moving plates whose interactions drive earthquakes, volcanoes, mountain building and continental drift.
Geoscientists report a Papua New Guinea rock that reached about 700 degrees C at 45 km depth and gained only about 100 degrees more by 90 km. A sample from one island cannot yet say whether the models or this zone is unusual.
Reality
Portsmouth-led researchers found the mantle recorded surface oxygen 3.4 to 3 billion years ago, up to 1.1 billion years before the Great Oxidation Event. Sulfur chemistry in apatite sealed inside zircon indicates oxidized surface material was already being carried down by some form of subduction, according to the Nature Geoscience study.
Reality
Panama was struck on Friday by a magnitude 7.7 earthquake near the village of Pitaloza Arriba, the USGS said. A USGS seismologist says the tsunami threat from the shallow, inland rupture has largely receded; shaking and aftershocks are the hazard that remains.
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Istanbul Technical University-led geologists date a previously unrecognized magmatic arc in northwestern Iran to about 101-97 million years ago. The Geoscience Frontiers study gives reconstructions of how the Neo-Tethys Ocean closed a dated subduction episode that earlier accounts of the region had missed.
Reality
Thomas Gernon's team used computer models to propose that a cliff up to 2 km high, formed as Rodinia split, wore away a billion years of Grand Canyon rock. Snowball Earth glaciers are cast as the accomplice, and testing the idea now depends on dating whether the rock was stripped before, during or after the ice.
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Ocean-bottom seismometers show the mantle under the 160- to 180-million-year-old Pacific Triangle was shaped by more than plate motion. YoungHee Kim of Seoul National University and colleagues say fossil fabric and present-day flow may coexist there, so plate-motion-only models of this patch need revising.
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Rice geophysicists Richard Gordon and Daniel Woodworth report that the whole solid Earth reoriented against its spin axis 56 to 48 million years ago. The tilt reconciles two clashing records of Pacific plate motion from the years just before the Hawaiian-Emperor bend formed.
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University of Florence geologists link quakes along nearly all of the 1,200-km Apennines to a front where deep crust peels into the mantle. One moving front would account for both the stretching and the squeezing, and for where Italy's quakes are likely to strike.
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LSU geologists imaged the plate sinking off Vancouver Island tearing apart, with part of the slab dropped about 5 kilometres along one fault. The finding suggests subduction zones end in stages, though its bearing on future Cascadia earthquakes is stated only as a possibility.
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Stefano Tavani's group combined Italy's earthquake record with GPS and satellite ground motion to argue that the lower crust beneath the Apennines is peeling away and sinking, a late-stage process he calls unzipping.
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A simulation that was never tuned to the Tasman Sea, a 200-million-year plate reconstruction and a lead-isotope signature that takes over a billion years to form all point to the Lord Howe and Tasmantid seamount chains sharing one source.
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An Adelaide-led team reports that magma feeding volcanoes in Western Australia's Pilbara Craton drew on a source that already held water, and proposes a pre-plate-tectonic process called dripduction to explain how it got down there.
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A Southampton-led study in Geology places an 800-million-year-old escarpment across ten future US states and has it removing up to 8 km of rock long before the Colorado River existed.
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