Volcanic arc Continental crust Lithosphere Oceanic crust Trench Lithosphere Asthenosphere
The Correct Answer and Explanation is:
Correct Answer:
These terms describe the features and processes involved in a convergent plate boundary, specifically oceanic-continental convergence.
Explanation
At a convergent plate boundary, two tectonic plates move toward each other. When an oceanic plate and a continental plate collide, the denser oceanic crust is forced beneath the less dense continental crust in a process known as subduction. This interaction forms several distinct geological features and layers in Earth’s structure.
The trench marks the point where the oceanic plate begins to descend beneath the continental plate. It is a deep depression in the ocean floor formed by the downward bending of the oceanic lithosphere.
Beneath the surface, the lithosphere, which includes both the crust and the uppermost part of the mantle, is involved in tectonic activity. The oceanic lithosphere, being older and denser, subducts under the continental lithosphere. As the oceanic plate sinks into the mantle, it begins to melt due to the high temperature and pressure conditions, releasing water and other volatiles into the overlying mantle wedge.
This process triggers partial melting in the asthenosphere, the semi-fluid layer beneath the lithosphere. The generated magma is less dense and rises through the continental crust, leading to the formation of a volcanic arc—a curved chain of volcanoes on the overriding continental plate. Famous examples include the Andes Mountains along the western coast of South America.
The continental crust in this region is typically thicker and more buoyant than oceanic crust. As a result, it resists subduction and instead experiences deformation, such as folding, faulting, and uplift.
In summary, the interaction between the oceanic and continental lithosphere at a convergent boundary results in key features: trenches, volcanic arcs, and mountain formation. It also drives important geological processes like earthquakes, volcanic activity, and crustal recycling, which are central to the theory of plate tectonics.
