New Haven Independent

Southern is sharing a two-year, $329,000 National Science Foundation grant with the Massachusetts Institute of Technology and Ohio State University to analyze and better date the rocks, collected over six Antarctic trips by Thomas Fleming, associate professor of earth science at SCSU.

Knowing the age and composition of the rocks could reveal information about the molten mantle that lies under the thin surface crust of the planet, Fleming said.
Rock that rises to the surface is one of the only clues to the mantle.

“Volcanic rocks help us understand the interior of Earth. It’s like what bubbles up through the crust of a cherry pie tells you what’s in the pie,” he said.

The data may also explain periodic mass extinctions of animals, including one about 65 million years ago that wiped out the remaining dinosaurs. A type of volcanic flooding last seen in 1783, seems to correlate with the catastrophic loss of life, he said.
The upwelling and spreading lava does not eject tons of ash into the atmosphere, but it releases gases that apparently can alter the climate.

Many people think of Antarctica as a blank white wasteland, and much of it is. But the eastern half of the continent is separated by the craggy Transarctic Mountains.
The mountains formed as the continental plates constituting Gondwanaland began to separate. South America, Africa and India drifted away from Antarctica, opening lines of volcanoes where the crust was stretched thin, Fleming said.

But the Antarctic volcanoes were not cone-shaped, and did not spew fountains of lava. Instead, molten rock sprouted up through the crust and then spread, like flood water. Most of this magma was basalt, like East Rock and West Rock.

Antarctica was farther north, and warmer at the time. Consequently, geologists find fossils of fish, trees, and bivalves, between periodic floes of lava, suggesting repeated lava spreads.

This type of volcanic event is rare, and was last seen in Iceland in 1783. More than three cubic miles of lava rose and diverged. The winter of 1784 was one of the coldest and longest in American history.

A similar event apparently occurred in India right about the time that the dinosaurs disappeared, approximately 65 million years ago, Fleming said.

In fact, lava “floods” seem to precede many extinction events over geological time, he said. Beneath the lava and layers of sediment is rock that is about 500 million years old.

Fleming said scientists in the project are interested in more precisely dating chunks of the Transantarctic Mountains, remnants of the most recent eruption. The material is about 180 million years old, plus or minus a few million years, he said.

MIT researchers developed a process that can increase dating accuracy to within 50,000 years, Fleming said. This information could show whether upsurges of lava precede global climate events and extinctions, he said.

Knowing precise ages of the rocks will also allow geologists to determine how the continents separated — did they tear, or rip apart like a zipper?

The MIT process involves extracting zircon crystals from the rock samples.
Zircon contains minute amounts of uranium, which very slowly decays radioactively into lead.

MIT researchers are able to measure extremely low levels of uranium and lead isotopes and know the half-lives of uranium isotopes with great precision. Thus, they are able to very accurately determine the age of these volcanic rocks.

First, students at SCSU and Ohio State will conduct geochemical analysis of the rocks, another way of establishing a timeline of volcanic events.

As molten materials rise to the surface, they cool. This causes crystals of minerals to form.

Different minerals solidify at different temperatures, permitting scientists to track the path of the lava. Magma also becomes contaminated with chemicals that it passes by on its way to the surface, providing information about the characteristics of rock that is far too deep to drill.

“All of this helps us understand the ages and relationships of the rock outcroppings, and the origins of the rocks,” Fleming said.

Examining upwellings of lava is one of the few ways geologists have of gleaning information about the mantle, which is about 1,800 miles thick.

Much information comes from measuring the reflections and diffractions of shock waves caused by earthquakes. The mantle is a mixture of iron, magnesium, aluminum, silicon, and oxygen with a plastic consistency due to the enormous pressure and temperature, which ranges from about 1,000 degrees to 7,200 degrees near the liquid iron core.

Continents slide around on the mantle, which slowly churns, ascending to create new crust and and descending to re-melt existing crust. The continental crust is an average of about 20 miles thick. The deepest drilled holes are no more than six or seven miles.