Cascadia Subduction Zone: A Seismic Threat. UPSC

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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

CASCADIA SUBDUCTION ZONE