Results from an expedition to the sea floor near the Hawaiian Islands show evidence that the deep Earth is more unsettled than geologists have long believed. A new University of Rochester study suggests that the long chain of islands and seamounts, which is deemed a "textbook" example of tectonic plate motion, was formed in part by a moving plume of magma, upsetting the prevailing theory that plumes have been unmoving fixtures in Earths history. The research will be published in the August 22 issue of Science.
"Mobile magma plumes force us to reassess some of our most basic assumptions about the way the mantle operates," says John Tarduno, professor of earth and environmental sciences at the University. "Weve relied on them for a long time as unwavering markers, but now well have to redefine our understanding of global geography."
Traditionally, the islands were thought to have formed as the massive Pacific plate, the largest single section of Earths crust, moved sluggishly between the Americas and Asia. A plume, or "hot spot," brought super-heated magma from deep in the Earth to close to the crust, resulting in concentrated areas of volcanic activity. As the Pacific plate moved across this hot spot, the plume created a long series of islands and subsurface mountains. Though this chain of seamounts seemed like a perfect record of Pacific plate movement, a strange bend in the chain, dated at about 47 million years ago, troubled some geologists. To most, however, this bend was taken as the classic example of how plates can change their motion. In fact, a figure of the bend can be found in nearly all introductory text books on geology and geophysics.
Jonathan Sherwood | University of Rochester
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