Testing the Volcano Mantle Plume Theory with Corn Syrup

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Hot springs in Yellowstone. Photo by C.Sagan

For decades scientists have argued over the presence, or absence, of mantle plumes, huge jets of molten rock that begin near the Earth’s core and rise up through the overlying material, or mantle. The tectonic plates composing the Earth’s surface move slowly across the plumes, and, according to scientists who give credence to the plume theory, that’s when a line of volcanoes (think the Hawaiian Islands, which are located far away from the edges of tectonic plates, the typical place where a volcano would form) are created.

And Yellowstone, a site known and loved for the supervolcanic activity seen there, has been at the center of this “heated” debate.

“Yellowstone is one key area where arguments against plumes are focused,” Christopher Kincaid, a geophysical fluid dynamicist at the University of Rhode Island, told Yahoo News.

Kincaid decided to test the mantle plume theory. But he did so by making the assumption that even though mantle plumes are generally used to explain volcanoes found far from tectonic plate borders, they could also rise up in subduction zones, areas near the edge of tectonic plates where one plate grinds beneath another.

To create the experiment, he and his students used a 200-gallon, rectangular tank filled with corn syrup.

“We use a very sticky, high-viscosity grade of corn syrup to represent the Earth’s mantle for a couple of reasons,” Kincaid said, going on to list corn syrup’s lack of inertia, temperature-dependent viscosity, and non-toxicity.

When Kincaid heated up a section of the tank’s floor, a jet of syrup shot up, showing that a split mantle plume could replicate real life geological occurrences.

“Most plume arguments only consider a simple view of a plume, rising into an otherwise stagnant system,” he said. “We found that plumes near subduction zones are like a prairie dog sticking its head up from its hole during a tornado.”

Kincaid adds that students love watching the experiment.

“We often get large crowds gathered in the lab when we are running these things,” he said. “The room is dark and the plumes are illuminated with micro tracers that sparkle and glow in the light sheets we shine through the tank. It is like you are looking directly into the Earth’s insides.”


Source: news.yahoo.com