Oct. 28, 1998 WASHINGTON, D.C. - A multidisciplinary group of scientists is challenging the century old theory that long lava flows must be formed by massive, but short lived, volcanic eruptions. Their research, reported in the Journal of Geophysical Research, suggests that some ancient flows of up to 100 miles in length built up gradually over years, rather than quickly in just days. This finding could have broad implications for the study of Earth and nearby planets.
One result of long but slow moving lava flows may have been global cooling caused by continuing emissions of sulphur dioxide. This cooling could have caused many major extinctions during the past 500 million years. For example, a major eruption in the North Atlantic might have wiped out most dinosaurs by eliminating their plant food supply, even before the presumed asteroid impact that finished the job.
The study is not limited to Earth. Lava flows significantly longer than any known on Earth have been observed on Venus, Mars, and the Moon, and their excellent exposure, coupled with improved spacecraft imagery may actually make them easier to study.
The latest findings on long lava flows are reported in the November 10 issue of the Journal of Geophysical Research, published by the American Geophysical Union. A special section of the journal is devoted to follow-up studies developed from an AGU conference at James Cook University in Townsville, Queensland, Australia. The meeting brought together volcanologists working on active flows in various parts of the world, other volcanologists analyzing flood basalt lava flows, planetary geologists, marine geologists, theoreticians, and economic geologists studying ancient ore-bearing lava flows.
The duration of a lava flow affects the amount of sulfur dioxide released into the atmosphere and therefore the degree of global cooling it causes. This cooling effect was noted following the relatively small eruption of the Laki volcano in Iceland in 1783. Therefore, the study of both active lava flows and ancient long lava flows can help in the assessment of future hazards. For example, there is now is an increased awareness of the role of lava tubes, through which molten lava can be transported over great distances with little loss of temperature. These tubes may play a role in future volcanic eruptions by carrying large amounts of lava to distant populated areas, as they have in the past.
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