Scientists use a shortcut to get clues from deep ocean

Expedition, No. 345 photo
Scientist examine rock core from Hess Deep

Out of sight of land in the Pacific another group of scientists is trying to make sense of the undersea activities in that part of the world.

This is the scientific complement of the “JOIDES Resolution” research vessel, and they are taking a shortcut.

The “JOIDES Resolution” is a frequent visitor to Costa Rica’s Pacific ports, and has participated in a series of scientific exploration off the coast.

The main area of study is the activity beneath the sea floor that can cause horizontal movements of up to 8 centimeters (a bit less than 3.5 inches) a year as the earth pushes up magma.

That research relates to the forces that forced up Costa Rica’s mountains, energizes its volcanoes and continues to rattle the country periodically. Unlike a lot of scientific expeditions, this one is transparent with an educational dimension, so daily activity becomes discussion topics.

This expedition, No. 345, is headed by Jonathan Snow of the University of Houston, Texas, and Kathy Gillis of the University of Victoria, Canada.

The drilling ship “JOIDES Resolution” is now on station above what is known as Hess Deep Rift about 2 degrees above the equator. Previous expeditions sought to sample the rock deep under the sea floor by drilling to it. But the presence of the rift, sort of an undersea canyon, provides a shortcut, the expedition explained in a recent summary. The deep cut in the ocean floor allows the crew to avoid a lot of drilling.

The rock surface at the bottom of the rift is estimated to be just about a million years old, a real youngster in geological terms. And this is what the scientific crew calls a tectonic window.
The rift is not far from the intersection of the Pacific, Nazca and Cocos tectonic plates.

The Cocos is the one that keeps pushing under and against the lighter Caribbean plate to bring earthquakes to Costa Rica. The summary of Expedition No. 345 describes its goal this way:

“The objective of this project is to sample for the first time, primitive magmatic rocks of the lower crust in the oceanic Pacific. These samples will help scientists seek to understand the manufacturing process of the oceanic crust at a fast-spreading rift, but also to document the effect of cooling the young crust by seawater, and thus the importance of chemical exchanges between the crust and the ocean. They control the chemical evolution of the oceanic crust before recycling into the mantle via subduction zones, and play a fundamental role in geochemical cycles across the globe.”

As magma is pushed to the surface, it cools into basalt and an igneous rock called gabbro, said the summary.

A previous expedition obtained samples of gabbro from a deep drilling also off the isthmus in the Pacific.

A member of the expedition, Jean-Luc Berenguer, reported via the “JOIDES Resolution” Web site this week that the drilling team had brought up core samples of rock from the Hess Deep, which is about 5,000 meters (about 16,400 feet) down.

In fact, the scientists have been demonstrating the force of the water by lowering polystyrene objects which are compressed into a much smaller size in the deep ocean. This is mostly as demonstrations to school children who are viewing the work electronically.

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