All posts tagged: Mantle

Antarctic seismic data points to an ancient structure circling Earth’s core

Antarctic seismic data points to an ancient structure circling Earth’s core

Published by Jenni Sidey

A layer only a few to a few dozen kilometers thick may be draped across the boundary between Earth’s core and mantle, and researchers say it likely consists of ancient ocean floor pushed deep underground over geologic time. That is the picture emerging from a study led by The University of Alabama, published in Science Advances, which used seismic data from Antarctica to probe a vast stretch of the Southern Hemisphere nearly 2,000 miles below the surface. The team found evidence that ultralow velocity zones, or ULVZs, are not just isolated patches in a few places. Instead, they may be widespread along the core-mantle boundary. These zones slow seismic waves and appear denser than the surrounding deep mantle. The researchers argue that the best explanation is old oceanic material that sank through subduction, then spread and accumulated along the bottom of the mantle. “Seismic investigations, such as ours, provide the highest resolution imaging of the interior structure of our planet, and we are finding that this structure is vastly more complicated than once thought,” said …

The hidden mantle flow shaping Yellowstone’s supervolcano

The hidden mantle flow shaping Yellowstone’s supervolcano

Published by Jenni Sidey

A sideways flow of hot mantle rock, not a deep plume rising from near Earth’s core, may be feeding one of the planet’s most closely watched supervolcanoes. That is the picture emerging from a new study of Yellowstone, where researchers built a three-dimensional model of western North America and traced how magma could form, move and collect beneath the region. Therefore, their conclusion points to a broad eastward “mantle wind” beneath the continent. This wind helps generate melt in the shallow mantle and helps shape the tilted underground system that supplies Yellowstone’s volcanism. The work, published in Science, comes from a team at the Institute of Geology and Geophysics of the Chinese Academy of Sciences. It tackles a long-running question at Yellowstone, where three caldera-forming eruptions have occurred in the past roughly 2 million years. These include the Huckleberry Ridge supereruption 2.1 million years ago and the Lava Creek supereruption 0.63 million years ago. Beneath Yellowstone For years, supervolcanoes were often pictured as holding large, long-lived magma chambers in the crust, pools of liquid melt …

Gold’s origins lie beneath the ocean deep inside the Earth’s mantle

Gold’s origins lie beneath the ocean deep inside the Earth’s mantle

Published by Jenni Sidey

The first step in gold’s journey does not happen in a mine, a fault, or a hydrothermal vent. It begins far deeper, in mantle rock melting beneath the seafloor. That is the picture emerging from new work led by Dr Christian Timm, a marine geologist at the GEOMAR Helmholtz Centre for Ocean Research Kiel. Studying volcanic glass from the Kermadec island arc north of New Zealand, the team found that gold-rich magmas in this setting appear to be tied not to a single burst of melting, but to repeated, water-aided melting in the mantle below subduction zones. Island arcs are the curved chains of volcanoes that form where one oceanic plate sinks beneath another. These regions are already known for hosting some unusually gold-rich seafloor sulfide deposits. What has remained unsettled is why the magmas feeding those systems can carry so much gold in the first place. The chain bag dredge is being hauled back on board during the sampling expedition in the South Pacific with the research vessel SONNE. (CREDIT: Christian Timm) “Our research …

Scientists create the first global map of rare, deep-mantle earthquakes

Scientists create the first global map of rare, deep-mantle earthquakes

Published by Jenni Sidey

Stanford University researchers have pulled back a curtain on a hidden part of Earth that rarely makes headlines. Their new work maps a strange kind of earthquake that starts deep below the crust, inside the continental mantle. The team says the map could help you understand how earthquakes begin, even the ones that shake your neighborhood. The study, published in Science, comes from Shiqi (Axel) Wang and geophysics professor Simon Klemperer at the Stanford Doerr School of Sustainability. They built what they call the first global map of these rare “continental mantle earthquakes,” events that happen beneath the crust but away from major subduction zones. “Until this study, we haven’t had a clear global perspective on how many continental mantle earthquakes are really happening and where,” said Wang, a former PhD student in Klemperer’s lab. “With this new dataset, we can start to probe at the various ways these rare mantle earthquakes initiate.” These quakes are usually too deep to do much at the surface. Still, their odd birthplace may give scientists a cleaner view …

Earth’s core is leaking vast amounts of gold through the mantle, study finds

Earth’s core is leaking vast amounts of gold through the mantle, study finds

Published by Jenni Sidey

Researchers at Göttingen University have uncovered new evidence that some of Earth’s most precious metals began their journey far deeper than once thought. Working with volcanic rocks from ocean islands, the team shows that gold and related metals can leak from Earth’s core, move through the mantle, and eventually reach the crust. The study, published in Nature, was led by geochemists Nils Messling and Matthias Willbold. Their work focuses on tiny chemical differences locked inside volcanic rocks formed far below the surface. These differences help trace where the material came from and how it moved through the planet. “When the first results came in, we realized that we had literally struck gold!” Messling said. “Our data confirmed that material from the core, including gold and other precious metals, is leaking into the Earth’s mantle above.” Researchers from Göttingen found tiny traces of the precious metal Ruthenium with an anomalous isotopic composition in lavas from Hawaii. The new findings prove that the Earth’s core is leaking metallic material, including gold and other precious metals. (CREDIT: United …