Expedition to second undersea canyon will study differences in ocean crust construction

The second Duke University-led expedition since 1999 to a deep underwater canyon will take geologists to another place in the eastern Pacific Ocean where new sea floor was forged out of volcanic lava within the past several million years.

The Pito Deep trough, positioned as deep as 19,600 feet below the ocean’s surface just west of Easter Island, will offer scientists a rare chance to study the internal geology of such ocean floor crust making processes.

The internal geology is accessible in the rift because it opens up the geologically young crust like a layer cake slice as thick as 1 1/2 miles, exposing now cooled and hardened conduits that once channeled molten rock towards the ocean floor surface. “Our investigation will look at the architecture of the crust and the composition of the rock that’s there,” said the expedition’s chief scientist, Jeff Karson, who is a geology professor with Duke’s Nicholas School of the Environment and Earth Sciences. “There will always be surprises,” Karson added. “We know so little about the submerged part of our planet that we find something new and exciting virtually every time we travel to the seafloor.”

Working from the Woods Hole Oceanographic Institution-based research ship R/V Atlantis, the scientists expect to be positioned over Pito Deep between Jan. 31 and Feb. 28.

A Nicholas School web site http://www.nicholas.duke.edu/pitodeep/ will be following the action as the scientists use the research submarine Alvin to explore the canyon’s walls, as well as dispatching an underwater robotic craft called Jason II to make photos and videos of the rockscape.

In 1999 Karson was also chief scientist on an expedition aboard the same ship to a larger eastern Pacific canyon called Hess Deep, located near the Galapagos Islands. Both Hess Deep and Pito Deep cut into crust created along different stretches of the East Pacific Rise, part of the volcanic ocean ridge system that circles the globe.

In a continuing process, new ocean crust forms at the East Pacific Rise when hot molten rock — called “magma” — erupts and cools in subsurface magma chambers. As it cools and solidifies, the resulting newly made crust then creeps away from the ridge axis like a slow motion conveyor belt. The new expedition will target differences between Pito Deep and Hess Deep rather than the similarities.

New crust made at Pito Deep creeps away from the East Pacific Rise at a rate greater than 144 millimeters a year, which geologists call “superfast.” That contrasts with a migration rate of only 110 millimeters at Hess Deep, considered merely “fast.” A millimeter is about 0.4 inches. “Our upcoming work at Pito Deep aims to explore whether there are identifiable differences in the structure and composition of ocean crust as a function of those differing spreading rates,” said Emily Klein, a Nicholas School associate geology professor who will be among the expedition’s other principal investigators.

Karson and Klein will be joined by three other principal investigators, David Naar of the University of South Florida, Richard Hey of the University of Hawaii and Jeff Gee of the Scripps Institution of Oceanography in California.

Other participating scientists will include Bob Varga of the College of Wooster in Ohio, Katherine Gillis of the University of Victoria in British Columbia, Stephen Hurst of the University of Illinois and Christopher Popham of the University of Rhode Island.

Five graduate students from Duke and other institutions will also participate in the cruise. Klein, Varga, Gillis and Hurst were previously on the 1999 Hess Deep cruise along with Karson.