Some Pacific Ocean Trenches Are Younger Than Believed

the JOIDES Resolution

Using the International Ocean Discovery Program research ship JOIDES Resolution, researchers have examined deep trenches in the Pacific Ocean. (Texas A&M photo)

A team of international scientists that includes a Texas A&M University researcher has found that parts of the deep trenches in the Pacific Ocean are much “younger” than previously believed – perhaps as much as 50 million years – and this could change current beliefs about how such deep-ocean trenches form.

The team, which includes Kara Bogus of Texas A&M’s International Ocean Discovery Program (IODP), has had its work published in the current issue of Nature Geoscience.

Using the research ship JOIDES Resolution, the team examined core samples extracted from a subduction zone south of Japan. The samples were taken from water about 4,800 feet deep in the Pacific floor.

A subduction zone is a huge underwater boundary that marks the collision between Earth’s tectonic plates. They are pieces of crust that slowly move across the planet’s surface over millions of years. When two tectonic plates meet at a subduction zone, one bends and slides underneath the other.

Such subduction zones were not identified until the 1960s, but they occur all around the Pacific Ocean, and are often referred to as the “ring of fire” because they are responsible for many of the world’s largest earthquakes, tsunamis and volcanic eruptions.

“From the core samples, we were able to date the sediments both with fossils and records of Earth’s past magnetic field reversals,” Bogus, who serves as an expedition project manager and staff scientist at IODP, explains.

“We found that this igneous crust is much younger – about 50 million years – than we originally thought. The fact that it is younger, coupled with its chemical composition, tells us how the subduction zone began.”

She adds that discovery is significant because “one of the biggest questions remaining in plate tectonics is how subduction zones start, or ‘initiate.’ When these plates push under each other into the Earth, hot magma is created that erupts from volcanoes on the surface plate, such as has occurred in the Northern Mariana Islands. It’s half the story in plate tectonics. We understand well the other half (how the plates move apart from each other and create new crust), but we are just beginning to understand this half.”

“Overall, our results mean that we need to modify our subduction inception models.”

IODP is an international scientific drilling program funded by the following agencies: National Science Foundation (USA), Ministry of Education, Culture, Sports, Science and Technology (Japan), European Consortium for Ocean Research Drilling, Ministry of Science and Technology (People’s Republic of China), Korea Institute of Geoscience and Mineral Resources (South Korea), Australian/New Zealand Consortium, Ministry of Earth Sciences (India), and Coordination for Improvement of Higher Education Personnel (Brazil).

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Media contact: Kara Bogus at (979) 845-0506 or bogus@iodp.tamu.edu or Keith Randall, News & Information Services, at (979) 845-4644 or keith-randall@tamu.edu


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