![]() ![]() ![]() "It's been very difficult to image the mantle below Hawaii, simply because it's so far away from seismic-sensor networks," van der Hilst said. But this kind of data has been limited for Hawaii. (See "New Magma Layer Found Deep in Earth's Mantle?")Ī technique called seismic tomography uses the sounds of earthquakes rippling through the planet and bouncing around to detect such plumes, or hot spots. Within a few miles of the crust, the rock decompresses, melts, and often oozes-or erupts-out of the Earth's surface. ![]() The outer core heats the mantle's bottom rocks into buoyant putty, which rises toward the crust, as if in a lava lamp. Volcano formation starts where Earth's mantle-the planet's thickest rock layer-meets the molten outer core, some 1,800 miles (2,900 kilometers) below the surface. (Related: "Hawaii's 'Gentle' Volcano More Dangerous Than Thought.") It can't be linked directly below," said geophysicist Robert van der Hilst of MIT, co-author of the new study, led by his colleague Qin Cao and appearing online today in the journal Science. The island, the youngest in the chain, is traditionally thought to be above the purported plume.Īlthough the new evidence flies in the face of the giant-plume theory, "we can't rule out a narrow plume below the island, but the main source comes from a different place. Until now, the researchers say, good seismic data on the region has been scarce, so it was tough to question the traditional explanation: that a stream of hot rock directly from around Earth's core formed the 3,100-mile-long (5,000-kilometer-long) chain of islands and undersea mountains in the Pacific Ocean.Īs Earth's crust slid over the plume, as if on a conveyor belt, the erupting seafloor built mounts, mountains, and islands out of layers of cooled lava over tens of millions of years-or so the conventional wisdom goes.īut after analyzing 20 years' worth of earthquake data, geophysicists say they've found an 800-mile-wide (1,300-kilometer-wide) region of hot rock in the Hawaiian region-but nothing beneath the Big Island of Hawaii. But it's not a plume running straight from the core to the surface-and it's hundreds of miles west of the nearest Hawaiian island. Scientists say they've found solid evidence of a giant mass of hot rock under the seafloor in the region. (See pictures of a recent eruption Hawaii's Kilauea volcano.) Hawaii's traditional birth story-that the volcanic islands were, and are, fueled by a hot-rock plume running directly to Earth's scorching core-could be toast, a new study hints. ![]()
0 Comments
Leave a Reply. |