Question

Crustal thickness is maximum at the ________.

• A. ocean-ocean convergent plate boundary
• B. ocean-continent convergent plate boundary
• C. continent-continent convergent plate boundary
• D. continent-continent divergent plate boundary

Answer 1

The Correct Option is C

The question asks where crustal thickness is maximum among given plate boundary types. To answer this, we need to understand the nature of different tectonic plate boundaries and their geological features:

1. Ocean-Ocean Convergent Plate Boundary: At these boundaries, two oceanic plates collide, and one subducts under the other due to its density. Volcanic arcs and oceanic trenches are common features here. The crustal thickness is not at its maximum because oceanic crust is denser and thinner than continental crust.
2. Ocean-Continent Convergent Plate Boundary: Here, the oceanic crust subducts under the continental crust. This leads to the formation of volcanic mountain ranges and deep oceanic trenches. Although the continental crust is thicker than the oceanic crust, this type of boundary does not exhibit maximum crustal thickness.
3. Continent-Continent Convergent Plate Boundary: When two continental plates converge, they both resist subduction due to similar densities and thicknesses. Instead, they crumple and fold against each other, leading to the formation of large mountain ranges such as the Himalayas. This results in significant crustal thickening, making it the location of maximum crustal thickness.
4. Continent-Continent Divergent Plate Boundary: At these boundaries, continental plates move apart. This leads to the formation of rift valleys and thinning of the crust, as magma rises to form new crust. The crust here is relatively thinner, not thicker.

Based on these explanations, the correct option is the continent-continent convergent plate boundary, where crustal thickness is maximum due to the crumpling and folding of the continental plates leading to mountain formation.

In summary, during a continental-continental convergence, significant crustal thickening occurs as neither plate is subducted. Instead, they collide, resulting in folded mountain ranges and the thickest crust.