The average radius of Earth is 6,371 km. If the average thickness of oceanic crust is 7.5 km and the average thickness of continental crust is 35 km, what fraction of Earth's radius is each type of crust? Convert the values from the km to the mile.

Another term for glacial erosion is abrasion. Abrasions occur when particles scrape against one another, which causes erosion. The friction that is caused in an abrasion loosens debris from the glaciers, causing them to fall away. Abrasions can occur in many ecosystems. Rocks, waves, gravity, wind, and running water can all cause abrasions. Hope this helps.