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CASCADIA SUBDUCTION ZONE

11th June, 2024

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Picture Courtesy: https://ktvl.com/

Context: A comprehensive survey of the Cascadia Subduction Zone reveals complex structures, segmentation, and geological features, aiding earthquake forecasting efforts.

Details

  • A new study, published in Science Advances, has produced the first comprehensive survey of the complex structures beneath the seafloor of the Cascadia Subduction Zone, a 600-mile-long strip off the coasts of southern British Columbia, Washington, Oregon, and northern California.

Subduction Zone

A subduction zone is a region along Earth's crust where two tectonic plates meet and collide, creating a geologically significant and potentially hazardous area. The process involves the convergence of denser oceanic crust with a less dense continental or another oceanic plate, known as subduction.

The subducting plate plunges into the mantle, where it can be recycled back into the Earth's interior. Subduction zones have a deep oceanic trench, an accumulation wedge, and a volcanic arc, releasing trapped water that lowers the melting point of the overlying mantle rock, forming a chain of volcanoes.

These zones are hotspots for earthquakes, with megathrust earthquakes occurring along their boundaries. They play a crucial role in shaping Earth's surface features, contributing to mountain building and recycling crust.

●Understanding subduction zones is vital for assessing earthquake and volcanic eruption risks, developing better prediction models, and developing preparedness strategies.

Cascadia Subduction Zone (CSZ)

  • It is a 960 km fault located off the Pacific coast, extending from northern Vancouver Island in Canada to Northern California in the United States.
  • It is capable of producing 9.0+ magnitude earthquakes and tsunamis that could reach 30 m.
  • The zone is a long, sloping subduction zone where the Explorer, Juan de Fuca, and Gorda plates move to the east and slide below the larger mostly continental North American Plate.
  • The region is influenced by tectonic processes such as accretion, subduction, deep earthquakes, and active volcanism of the Cascades.
  • Notable eruptions include Mount Mazama 7,500 years ago, Mount Meager massif 2,350 years ago, and Mount St. Helens in 1980.

Source:

PHYS.ORG

Wikipedia

PRACTICE QUESTION

Q. Which of the following conditions are most likely to be present at a subduction zone?

1. A deep oceanic trench on the side of the denser plate.

2. A volcanic arc on the side of the overriding plate.

3. A mountain range on the side of the subducting plate.

4. A zone of high seismic activity along the plate boundary.

5. A region where a new oceanic crust is being created.

How many of the above statements are correct?

A) Only two

B) Only three

C) Only four

D) All five

Answer: B