Context: Large masses, such as ice sheets or glaciers, can depress the crust of the Earth into the mantle. The depression usually totals a third of the ice sheet or glacier's thickness. After the ice sheet or glacier melts, the mantle begins to flow back to its original position, pushing the crust back up. This post-glacial rebound, which proceeds very slowly after the melting of the ice sheet or glacier, is currently occurring in measurable amounts in Scandinavia and the Great Lakes region of North America.

Question: Where is post-glacial rebound occuring most?
Answer: Scandinavia and the Great Lakes region of North America.

Question: What has the ability to depress the crust of the Earth into the mantle?
Answer: Large masses, such as ice sheets or glaciers

Question: With what speed does post-glacial rebound occur?
Answer: very slowly

Question: How much of a glacier's thickness is usually involved during crust depression into the mantle?
Answer: a third of the ice sheet or glacier's thickness

Question: Where has post-glacial rebound stopped occuring?
Answer: Unanswerable

Question: What totals a thirs of the glaciers length?
Answer: Unanswerable

Question: What happens quickly after the ice sheet melts?
Answer: Unanswerable

Question: What pushes up the mantle of the Earth?
Answer: Unanswerable