Earth is nearly 4,000 miles deep, and other than the outermost few miles, is inaccessible to humans. Seismology is the only tool to accurately image the deep interior of Earth. Over the last few decades, seismologists have used the tool of seismic tomography to map out the interior of Earth (much like medical CT scan tomography to image the human body).
Ed Garnero, a geophysicist at Arizona State University, will share his research on Earth’s dynamic interior at the American Association for the Advancement of Science annual meeting on Feb. 13.
For nearly 30 years, Garnero has focused his research on the area between Earth’s uppermost mantle to the innermost core.
In his lecture “Interpreting Earth's Largest Internal Seismic Anomalies: Deep Thermochemical Piles,” Garnero will discuss how modern research shows that many surface processes on our planet are related to dynamic phenomena within. He will be sharing cutting-edge images of Earth's interior, which reveal two massive continental-sized blobs half-way to Earth's center that likely relate to where the most massive eruptions happen at Earth's surface.
“One blob is located beneath the Pacific Ocean, the other is nearly on the opposite side of Earth, beneath the Atlantic and part of the African continent,” says Garnero, a professor in ASU’s School of Earth and Space Exploration. “The massive blobs are important because they appear to play a role in convective processes, including where mantle plumes originate – plumes are thought to give rise to Earth's hotspot volcanoes.”
Observations, modeling and predictions show the inner Earth to be chemically complex and continuously churning and changing. Tomographic images constructed from seismic wave readings point to differences in the speeds of waves that go through the mantle. This difference in wave speeds provides a sort of map of the major boundaries inside the mantle – where hot areas are, where cold areas are, where there are regions that might be a different composition, etc.
“These continent sized blobs have properties that result in seismic waves traveling more sluggishly through them,” explains Garnero. “Our recent research adds to the body of knowledge that supports these blobs being chemically distinct from the rest of the mantle rock.”