History at the ends of the Earth

Geologist Samuel Mukasa

By Karl Leif Bates
U-M News Service

As a Ugandan teenager, Samuel Mukasa’s first encounter with snow was atop Mount Kilimanjaro. Ever since, the LSA geology professor has gone to great lengths to find new things.

He has journeyed to Antarctica nine times to search for traces of the “nucleus” of the super-continent Gondwana, from which Africa, South America, Australia, New Zealand, and the Indian Subcontinent are all believed to have flaked off over the ages.

Though the voyage seems a little extreme, it’s easier to understand continental drift by visiting this one frozen spot, rather than venturing to all of the continents in turn, Mukasa explains. “You have a fighting chance of understanding the story,” he says, “if you look at the margins”—namely the jagged edges of Antarctica and the corresponding points in the continents.

“We see things here that we see 2,000 kilometers away in New Zealand,” he says, jabbing a ruler at the Ross Sea on a colorful satellite photo of the entire continent that hangs in his office in the C.C. Little Building.

Most of Mukasa’s voyages to the frozen continent have been to the Ross Sea and McMurdo Sound where the U.S. research base is located. But his other excursions have explored Antarctica’s South Atlantic shore, where Africa was once anchored, and a high ridge of volcanic mountains that spans most of the continent.

Some trips Mukasa is on land, looking at ancient volcanic ridges that rose as Gondwana was torn apart. Other times he’s aboard a research ship, dredging up samples from the deep.

Regardless of the sampling methods, what he’s after are rocks, which he’ll subject to the latest in separation and purification techniques. Mukasa uses the relative abundance of trace elements to reconstruct the detailed timeline of how continents formed and broke apart.

Of course, having gone to the trouble of making the trip all the way to the Southern Hemisphere, Mukasa has stood at the South Pole four times. “I walked all the way around the Earth in five steps!” he says. He’s excited by such extremes, but they’re dangerous, too. “Last year, we had to keep dodging an ice floe that was the size of Rhode Island,” he says.

But that’s nothing compared to the year that the captain’s shortcut through the Beagle Channel led the ship onto an undersea mount that tore a gash in the port side of the vessel’s outer hull. It listed terribly, but did not sink.

Thankfully, the group was rescued and Mukasa hasn’t given up on extreme adventures. This summer he will voyage to the North Pole for the first time, dragging a bucket across the bottom of the Arctic Sea in a search for bits of volcanic glass. “This is kind of a dicey trip, because we may not get any data we can use. But you have to take chances in this business.”

Adapted from LSA Magazine
http://www.lsa.umich.edu/lsa/news/lsamagazine/