Scientists Study 100-Million-Year-Old Volcanism in the Indian Ocean
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Clues to Earth's internal dynamics may lie in the remote southern Indian Ocean, in a submarine plateau one-third the size of the United States. For the next two months, geologists with the Ocean Drilling Program (ODP), funded in large part by the National Science Foundation (NSF), will unearth the secrets of the Kerguelen Plateau, an example of a unique type of Earth feature, a large igneous province (LIP).
LIPs are areas where magma wells up from deep beneath Earth's surface and forms molten rock; they may be expressions of the largest volcanic events in the planet's history. One of the least understood features in the ocean basins, LIPs preserve a record of volcanism and may have affected Earth's past environment by altering ocean circulation, climate conditions and sea level.
A team of 28 scientists will study an LIP that originally formed from the Kerguelen Plateau and a now separate but related nearby feature, Broken Ridge. To investigate the history of Kerguelen Plateau and Broken Ridge, the scientific team will retrieve core samples from as deep as one kilometer below the seafloor using advanced drilling technology aboard the JOIDES Resolution, the world's largest scientific drill ship.
The JOIDES Resolution is scheduled to depart Fremantle, Australia, on December 12, and conclude the expedition on February 11, 1999. Mike Coffin of the University of Texas Institute for Geophysics and Fred Frey of the Massachusetts Institute of Technology will lead the scientific team. The scientists hope to resolve questions about the Kerguelen Plateau's eruption history by analyzing samples of sediment and lava collected in cores taken from deep beneath the seafloor. Since its formation, the plateau has subsided to water depths of more than a kilometer.
Earth has experienced massive volcanic episodes with magma emanating from the deep mantle many times. Such episodes were relatively common between 150 and 50 million years ago, but have been infrequent during the past 50 million years. Due to their inaccessibility beneath the oceans, few large igneous provinces have been sampled and dated for comparison with similar provinces on land, explains Bruce Malfait, ocean drilling program director at NSF. Adds Frey, "When results of the expedition are combined with previous seafloor drilling studies, the Kerguelen 'hot spot' will provide the best understood long-term record of hot spot volcanism."
Subsequent analysis of the core materials, both aboard the ship and in land-based laboratories, will enable scientists to reconstruct the volcanic history of this region, including both the timing of eruptions and changes in the chemical composition of the lavas.
States Coffin, "Large igneous provinces provide the only known record of ancient deep Earth dynamics. Kerguelen Plateau and Broken Ridge hold the history of one of the largest and longest-lived volcanic events on Earth. The results of this expedition will contribute greatly to our understanding of how mantle hot spots behave through time, and their possible effects on the global environment." The Kerguelen hot spot continues to erupt today at Heard and McDonald Islands in the Indian Ocean.
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