Dredging up the Truth

Annie Reisewitz

A team of scientists at Scripps Institution of Oceanography at UC San Diego collected rocks during an expedition to unexplored areas in the Gulf of California in hopes of acquiring a more detailed view of a region being split apart by the birth of an ocean.

“There were a couple of dredges that brought up some unexpected rocks that  might change the way we think about the early stages of rifting in the Gulf of California,” said Jared Kluesner, a Scripps graduate student who led the ten-day  expedition that took place from Oct. 2 to 13.

Over the past 12 million years, Baja has been slowly rifting apart -- pulling itself away from mainland Mexico -- resulting in the thinning of continental crust and eventual transition into young oceanic crust. A similar process took place 120 million years ago in the Atlantic Ocean basin, which scientists believe was once analogous to what the Gulf of California looks like today.

During the GEOFORM2009 (Geological Exploration of the Formation of a Rifted Margin) expedition, the scientists collected rock samples using a one-meter (three-foot)-wide rock dredge and imaged unusual geological features they encountered with a sub-bottom profiler known as CHIRP to see deeper into the rock structures.

On Oct. 5, three days after the research team departed San Diego aboard Scripps research vessel New Horizon, the scientists encountered a mega-pockmarked field, filled with giant holes formed along the seafloor.

“These pockmarks are huge — over a kilometer across in some cases and hundreds of meters deep,” said Scripps graduate student Sandra Kirtland in the GEOFORM2009 blog.

The science team also collected samples from various undersea mountains, including a sombrero-shaped seamount and another 1,900-meter (6,200-foot) deep seamount surrounded by a moat-like ring within the Farallon Basin. The Farallon Basin is a spreading center of young oceanic crust located in the southwestern region of the gulf that contains rift valleys more than 3,000 meters (9,800 feet) deep.

Kluesner used sound waves in conjunction with the information obtained from the rock dredges to create a detailed image of the geological structures below the seafloor. This research study will enable the science team to better understand the current geological processes taking place in the narrow strip of water that forms the Gulf of California.

“I hope the samples will provide new insight into the early evolution of the Gulf of California, and what we learn from these rocks can be applied to older rifted margins, such as the Atlantic Ocean,” said Kluesner.

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