How does a glacier move?

gravity

Explanation:

Gravity is the cause of glacier motion; the ice slowly flows and changes in response to gravity. A glacier molds itself to the land and also molds the land as it creeps down the valley. Many glaciers slide on their beds, which enables them to move faster.

from the original order (top to bottom) the new order will go

1 (founder)

4 (hawk)

2 (mutate)

3 (next generation)