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An Intellectual Adventure

From the Black Hills to the Mid-Ocean Ridges

Brian Tucholke says he’s “been a geologist from the time I first crawled off my baby blanket and grabbed a fistful of dirt.”

He grew up in the Black Hills of South Dakota, which rise out of the continent to expose layer upon layer of rocks laid down over billions of years. It’s a natural geological laboratory, and it was Tucholke’s playground.

“Almost the entire layer cake of geologic history, from the Pleistocene to the Precambrian Era, is sitting right there,” he said. “I spent a lot of time roaming around the Badlands hunting for fossils, finding minerals in abandoned mines in the Hills, hunting for native American artifacts, spelunking….”

Tucholke earned his B.S. degree at the South Dakota School of Mines & Technology. He graduated in 1968—just at the moment in scientific history when a new theory was revolutionizing our fundamental understanding of the earth. The theory, plate tectonics, explained how large sections of the earth’s surface were created by magma upwelling at mid-ocean ridges and destroyed when portions of older seafloor descend back toward the mantle in deep oceanic trenches.

The scientific excitement spurred Tucholke to turn his geologic eye toward the oceanographic frontier, and he entered the inaugural class of the just-established MIT/WHOI Joint Program.
 
“I mostly gave up the bedrock stability of the western mountains for the rolling seas,” he said. “MIT’s academic reputation and the field research opportunities at WHOI seemed like the ideal combination.” The village atmosphere of Woods Hole also tempered the culture shock of moving to Cambridge after his small-town boyhood in Hot Springs, South Dakota, population 2,300.

Tucholke focused his thesis work on the Greater Antilles Outer Ridge, a huge drift of seafloor sediments deposited by abyssal currents north of Puerto Rico.

“We hit the ridge with everything we could muster,” he said. He placed current meters in strategic locations, collected water temperature and salinity data with Nansen bottles, filtered seawater to study suspended particles in the deep currents, and cored the seafloor to look at sedimentary strata. “We even built a deep-sea camera that pogoed across the bottom with a trip wire to photograph current markers on the muddy seafloor,” he said.

With this smorgasbord of collected evidence, Tucholke could reconstruct how tectonic forces, abyssal ocean currents, and other factors combined to build and sculpt the ridge.

“It’s a very satisfying process of assembling little clues to reconstruct large-scale events that happened over long time periods,” Tucholke said. Having solved one relatively modest geologic puzzle in the Antilles, he just kept on going, using marine geological and geophysical tools to study all aspects of ocean-basin evolution from ancient rifting that created the first seam between continents to tectonics on modern mid-ocean ridges.

 “It’s been a self-propelling intellectual adventure,” he said.

After graduating in 1973, he joined Leg 35 of the Deep Sea Drilling Project off Antarctica in 1974. There, he said, he helped “piece together the geological history of how the Drake Passage opened,” as the tip of South America split from the Palmer Peninsula to provide a connection between the southern Pacific and Atlantic Oceans.

He then spent half a decade at the Lamont-Doherty Geological Observatory, drawn to its vast archives of untapped geophysical data collected in the 1950s and 1960s. But in 1979 he returned to WHOI, where he could combine a high level of intellectual stimulation with a less urban lifestyle. Along the way, he has mentored Joint Program students in subsequent generations and served as education coordinator in the Geology and Geophysics Department. In 1998 he was awarded the Henry Bryant Bigelow Chair at WHOI in recognition of his contributions to ocean sciences.

All told, Tucholke has logged 26 oceanographic cruises, including 15 as chief scientist, and in a humorous brief biography of himself, he wrote: “The mark of his passage can often be seen in the imprint of his cowboy boots, several decrepit pairs of which he has buried at sea in oceans ranging from the North Atlantic to the Bellingshausen Sea off Antarctica.”

His research has revealed the evolution of the Atlantic Ocean, from the continental margin to the Mid-Atlantic Ridge, since it began to form 180 million years ago. Recently he discovered previously unknown mid-ocean ridge structures, dubbed megamullions, which seem to resemble corrugated mountainous domes formed in continental areas that are being extended by tectonic forces, such as the western US. The finding brings him full circle, fostering new “fruitful interactions with continental geologists and allowing me to pursue interests back in the heartland of my youth,” he said.

“I always wanted to establish a Rocky Mountain Institution of Oceanography,” he said with a smile, “but it isn’t practical.”

Unfortunately, it will take many millions of years for tectonic forces in the western US to create an adequate harbor. “WHOI is the next best thing,” he said.

— Laurence Lippsett

Originally published: March 1, 2000