A enormous ocean floor lurks close to Earth’s core. Now, seismic imaging has revealed that it probably surrounds substantially — if not all — of the core.
This thin, dense layer is lodged roughly two,000 miles (three,200 kilometers) beneath Earth’s surface, among the core and the planet’s middle layer, named the mantle. And it may possibly encompass the whole core-mantle boundary, according to a study published April five in the journal Science Advances (opens in new tab).
To study Earth’s interior, seismologists measure earthquake waves that zoom by way of the planet and then back out to Earth’s surface. By seeing how these waves modify soon after passing by way of the distinctive structures inside Earth, researchers can make a map of what Earth’s innards appear like. Previous analysis identified a handful of isolated pockets of dense ocean crust close to the core. These pockets are named ultra-low-velocity-zone structures (ULVZs) due to the fact seismic waves travel really gradually by way of them.
“Only [approximately] 20% of the core-mantle boundary has been previously investigated for ULVZs, which have not been identified in all of these places,” lead study author Samantha Hansen (opens in new tab), an associate professor of geological sciences at The University of Alabama, told Reside Science in an e-mail. “It is achievable that this anomalous material covers the whole core.”
In the new study, scientists placed seismic gear at 15 stations positioned across Antarctica and collected information for 3 years.
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This study marks the very first time that higher-resolution imaging of the core-mantle boundary was created making use of information from the Southern Hemisphere. The layer itself is razor-thin compared with the core, which is 450 miles (724 km) across, and the mantle, which is roughly 1,800 miles (two,900 km) thick.
“The thickness does differ, based on place,” Hansen stated, with some spots measuring about three.1 miles (five km) thick and other individuals 31 miles (50 km) in thickness.
This ancient ocean layer probably created when Earth’s tectonic plates shifted, causing oceanic material to be carried into the planet’s interior at subduction zones, the places exactly where two plates collide and force 1 to dip beneath the other. More than time, “accumulations of subducted oceanic material gather along the core-mantle boundary and are pushed by the gradually flowing rock in the mantle,” according to a statement (opens in new tab).
Researchers believe the newly detected ULVZs are basically “underground mountains” that permit heat to escape from Earth’s molten core, according to the statement.
“The presence of this layer could buffer heat flow across the core-mantle boundary, which is vital due to the fact the temperature situations in this portion of the Earth have been shown to strongly influence the planet’s magnetic field,” Hansen stated.
Chunks of this hidden ocean floor may possibly also get swept up into mantle plumes — hot, upwelling jets of molten rock that fuel volcanic hotspots at the surface, such as in Hawaii, Hansen recommended.
“Additional, due to the fact mantle plumes are largely controlled by the thermal situations close to the core-mantle boundary, the temperature influence of ULVZs may possibly support dictate exactly where plumes kind,” Hansen stated.
The analysis group plans to expand their study by examining information collected from all accessible seismic stations in Antarctica.