Where would you expect to find the thickest crust on Earth?

Where would you expect to find the thickest crust on Earth?

• A. Continental mountain ranges
• B. Mid-ocean ridges
• C. Ocean basins
• D. Oceanic trenches

Answer: (A)

Crustal thickness varies a lot with tectonic setting. Continental crust is thicker than oceanic crust, and it becomes even thicker where continents collide and mountains form. In those collision zones, the crust is squeezed and stacked, creating a deep crustal root that extends downward into the mantle to balance the added mass. That combination produces continental crust that is typically tens of kilometers thick, and in major mountain belts it can reach around 60 km or more. Oceanic crust, by contrast, is relatively thin because it forms at mid-ocean ridges from upwelling mantle and solidifies into basaltic rock, usually about 5–10 km thick. Ocean basins don’t generally develop the huge crustal roots that mountains do, and trenches involve subducting oceanic crust rather than thick continental crust. Therefore, the thickest crust is found beneath continental mountain ranges.

Crustal thickness varies a lot with tectonic setting. Continental crust is thicker than oceanic crust, and it becomes even thicker where continents collide and mountains form. In those collision zones, the crust is squeezed and stacked, creating a deep crustal root that extends downward into the mantle to balance the added mass. That combination produces continental crust that is typically tens of kilometers thick, and in major mountain belts it can reach around 60 km or more.

Oceanic crust, by contrast, is relatively thin because it forms at mid-ocean ridges from upwelling mantle and solidifies into basaltic rock, usually about 5–10 km thick. Ocean basins don’t generally develop the huge crustal roots that mountains do, and trenches involve subducting oceanic crust rather than thick continental crust.

Therefore, the thickest crust is found beneath continental mountain ranges.