What happens during subduction? A. Dense continental crust slides over less dense oceanic crust. B. Dense oceanic crust slides under less dense continental crust. C. Dense oceanic crust slides over less dense continental crust. D. Dense continental crust slides under less dense oceanic crust.
The correct answer and explanation is:
Correct Answer: B. Dense oceanic crust slides under less dense continental crust.
Explanation:
Subduction is a geological process that occurs at convergent plate boundaries, where two tectonic plates collide. In most cases, oceanic crust, which is denser and thinner than continental crust, is forced beneath the continental plate. This process is called subduction and leads to the formation of a subduction zone.
Oceanic crust is mainly composed of basalt, a dense volcanic rock, while continental crust is largely made up of granite, which is less dense. Because of this difference in density, when the two types of crust collide, the denser oceanic plate sinks (subducts) beneath the less dense continental plate and descends into the mantle, the hot, semi-fluid layer beneath Earth’s crust.
As the oceanic plate is pulled deeper into the mantle, several things occur:
- Earthquakes are generated due to the immense pressure and friction between the plates.
- The descending plate melts because of the intense heat and pressure, forming magma.
- The magma rises through the continental crust, potentially leading to volcanic activity.
- A trench forms at the point where the oceanic plate begins to descend. A well-known example is the Peru-Chile Trench along the west coast of South America.
Subduction is a key component of the plate tectonics theory and plays a major role in the rock cycle, mountain formation, and recycling of Earth’s crust. It also explains the distribution of earthquakes and volcanoes along the so-called “Ring of Fire”, which surrounds the Pacific Ocean.
In summary, during subduction, dense oceanic crust slides under less dense continental crust, making option B the correct answer.