What causes isostatic rebound?

Isostatic rebound is the uplift and readjustment of the land after a glaciation. During the last glacial maximum, and other ice ages, the weight of the ice sheets pressed down on the land, causing it to sink and depress. However due to the relative elasticity of the mantle, once the ice melted, the land was able to rebound upwards. Some areas are continuing to do so today, such as Western Scotland. Landforms such as relict cliffs and raised beaches are evidence of this ongoing process.