Science Olympiad Dynamic Planet Practice Test

Which phenomenon describes the rise of land masses after the melting of ice sheets?

1. Mass wasting

2. Isostatic depression

3. Post-glacial rebound

4. Glaciation

The correct answer is: Post-glacial rebound

The phenomenon that describes the rise of land masses after the melting of ice sheets is known as post-glacial rebound. This occurs as the immense weight of large ice sheets compresses the Earth's lithosphere (the rigid outer layer of the Earth). Once these ice sheets begin to melt, the pressure is reduced, allowing the land beneath to slowly uplift or rise back to its original position. This process can take thousands of years and is an important factor in understanding the geological and ecological impacts of glacial retreat. The other options do not accurately describe this specific phenomenon. Mass wasting refers to the movement of soil and rock downslope due to gravity, which is unrelated to the effects of glacial melting. Isostatic depression describes the sinking of land masses under the weight of an ice sheet, but the question specifically concerns the rise that occurs after the melting of the ice. Glaciation refers to the period during which ice sheets expand over the land, not the subsequent rebound of the land itself. Thus, post-glacial rebound is clearly the correct answer as it directly pertains to the recovery of the land once the weight of the ice has been removed.