Works in Progress - Summer 2019

Searching for Seamounts

A seismologist maps the mountain range below the Pacific

By Rebecca McCarthy | June 3, 2019

Some of the biggest mountains are ones you’ll never see. They’re not shrouded in cloud but submerged by the blue waters of the Pacific. They run in a 3,600-mile-long, mostly underwater mountain range stretching from just southeast of the island of Hawaii, northwestward nearly to Russia. Called seamounts, these are mountains rising from the ocean floor that don’t reach the water’s surface.

This summer, marine seismologist Donna Shillington will spend two months aboard a research vessel to continue mapping the Hawaiian-Emperor Seamount Chain, using an array of high-pressure air guns and seismometers. The National Science Foundation is funding her research. She completed the Hawaii section last summer, and this summer will head northwest out of Hawaii.

Towed by the ship, the air guns blast the water with bubbles that produce sound waves that penetrate the ocean floor. The sound is at a low frequency that won’t disturb marine animals, Shillington says.

She will be analyzing the data she collects for the next two years, hoping to better understand how the earth works and what part submerged mountains play in its processes. Mapping geological structures beneath the seafloor, such as faults, may provide insight into how earthquakes and tsunamis are generated.

The Hawaiian Islands are home to some of the most active volcanoes on earth because, scientists believe, they lie over a hot spot where magma wells up from far beneath the surface. The Hawaiian hotspot is thought to have formed the entire Emperor chain as the Pacific Plate slowly shifted across it. The study will test whether the volume of magma released along the chain has changed over time.

Shillington is also hoping the new data will help her estimate the strength—which correlates with thickness—of the oceanic plate, where earthquakes can originate.

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