Meanwhile, back on the shore ... Garrett holds up a piece of ice that he'd broken on the rocks about half an hour ago. It's already melted partially around the grit that it was left lying on. This is a small-scale example of how glaciers can pick up rocks from the mountainside and carry them for miles and miles, grinding them smooth against other rocks as they go.

In fact, this is probably not the first time the rocks in this picture have been trapped in ice.