Discover giant structure near the Earth's core

The researchers found an unusually large structure of dense hot rock hidden deep within the Earth, below the Pacific Ocean.

The structure, called the UltraVolume Zone (ULVZ), is located at the boundary between the molten core and the Earth's hard mantle, just below the Marquesas Islands in French Polynesia in the South Pacific, according to the study. published on June 12 in Science magazine. An international team of researchers from the University of Maryland (UMD), Johns Hopkins University and Tel Aviv University, Israel, also found evidence that a previously defined ULTZ area beneath the larger Hawaiian Islands. much more than expected.

Simulation of the Earth's core. (Photo: Science Alert0.

ULVZ regions are located on the bottom of the Earth's erupting columns. The eruption is a geological feature where molten rock rises from the boundary between the outer core and the mantle to the outer crust of the planet, creating volcanic islands such as Hawaii and Marquesas. In fact, the ULVZ region below Hawaii is the largest example that researchers have ever known.

Scientists discovered ULVZ by analyzing seismic wave data, a type of wave that can reveal structures hidden beneath the planet's surface as it travels through the ground. Seismic waves generated from earthquakes travel thousands of kilometers underground. But because the materials they transmit have differences in density, temperature or composition, seismic waves can change their speed, be bent or scattered, creating a buzz that scientists have. detected by seismograph.

Using this data, researchers can visualize the rock beneath the Earth's surface and estimate the characteristics. In the latest study, the authors used a machine learning term called Sequencer to simultaneously analyze about 7,000 seismic tape recordings generated by hundreds of earthquakes of 6.5 degrees and above in the area. Pacific region from 1990 to 2018.

These waves are diffracted along the boundary between the outer core and the mantle, providing a comprehensive understanding of the Earth's structure deep down in the Pacific region. The team unexpectedly found that nearly half of the radioactive waves were scattered by three-dimensional structures near the boundary. They noticed many previously defined structures, but there was also a new ULVZ area below the Marquesas Islands.

The researchers deduced the presence of large ULVZ regions when special signals were detected beneath the Hawaiian Islands and the Marquesas Islands. "We suddenly found a large structure under the Marquesas Islands that no one knew it existed," said Vedran Lekic, co-author of the study at UMD. "This is really interesting because the research results show that the Sequencer algorithm can help us decode global seismic data in a way never before possible."