Aug. 28, 2008
PHOTO: UI geologist Ingrid Ukstins Peate is pictured beside a rock of volcanic origin while conducting fieldwork in China.
UI researcher helps rewrite Earth's volcanic history of 260 million years ago
A University of Iowa researcher is helping to rewrite the geologic story of one the Earth's most active volcanic periods -- one that included a mass extinction of life -- some 260 million years ago.
Volcanologist and planetary geologist Ingrid Ukstins Peate, assistant professor of geoscience in the University of Iowa College of Liberal Arts and Sciences, published her research online Aug. 24 in the journal Nature Geoscience. Ukstins Peate, with co-author and geologist Scott Bryan of the University of Queensland, Australia, write that the massive eruptions likely were due to basaltic lava reacting with a shallow ocean that once covered southwestern China, rather than as a result of large-scale uplift from plumes of magma rising from deep within the Earth's mantle to the surface, as many geologists think.
"We found evidence for the interaction of lava with ocean water at the beginning of this volcanic event," she said. "This is significant for two big reasons. It shows that this area was not highly uplifted because it had to form at ocean level, and volcanic activity produced giant explosive eruptions because heat from the lava caused the water to flash to steam.
"These volcanic eruptions were giant, of a scale humans have never seen on Earth, and orders of magnitude bigger than Mount St. Helens in 1980," she said. "Mount St. Helens erupted about a cubic kilometer of lava, whereas each of the eruptions in China were probably hundreds to thousands of cubic kilometers, and there were dozens to hundreds of eruptions, not just one."
In order to conduct their research, Peate and Bryan traveled to the Emeishan large igneous province, located in southwest China. Some geologists have described the region as one of the best examples of plume-induced uplift.
The way in which the eruptions occurred is significant, Peate said, because geologists generally agree that the period included a number of important events in Earth's history such as the break-up of the super continent Pangaea, a likely change in planetary climate, and a mass extinction of life on Earth.
"This time in Earth history has been linked to one of the largest mass extinction events we know about, where 96 percent of all ocean species and about 70 percent of all land species went extinct," she said. Giant explosive eruptions such as these may have impacted the planet's climate because large eruption columns could spread ash particles and toxic gasses into the upper atmosphere and around the globe."
Commenting on the likely impact of her research on the field of geoscience, she said, "This research helps us understand a dynamic, planet-impacting event a little better. It is difficult to study these kinds of events, because they have never occurred in human history, so there are no first-hand observations, but it is probably better for us that way."
Peate says that she plans to continue to study the cause of the volcanic events in order to provide a better understanding of Earth's past and to gain a better insight into current volcanic activity.
"Scott and I are very pleased our research produced results that we think will be interesting and relevant to the broader Geologic community. We hope to continue this avenue of research," she said.
Further information about the paper, "Re-evaluating plume-induced uplift in the Emeishan large igneous province," can be found with the article abstract at http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo281.html.
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