How does a glacier move enormous rocks?

Imagine pressing both hands against a rock as big as a car. It feels cold and rough under your palms. You push and push, but the rock does not budge one bit.

Yet in snowy mountains, rocks that big travel far from where they started. Something made of ice carries them. So how does a glacier move enormous rocks?

A glacier is ice so thick that a whole house could hide inside it. All that ice is incredibly heavy. Its own weight pulls the glacier slowly downhill, so slowly that you could never see it move.

Rocks also break off the steep mountain sides high above and tumble down onto the glacier. The ice holds them on its back like a giant tray, ready for a ride.

At the very bottom, the glacier presses down hard on the rocky ground, and that heavy squeeze melts a little of its ice into water. The water trickles into cracks in the rocks below and freezes again, gripping them like icy fingers. As the glacier keeps creeping forward, what do you think happens to a rock the ice holds tight?

The glacier tugs that rock right out of the ground and drags it along! We call this plucking, which means the moving ice pulling rocks loose from the ground. Rock by rock, the glacier gathers its load.

After plucking, the rock sits stuck inside the ice and goes wherever the glacier goes. Day after day, for many years, the heavy ice carries it down the valley. Even rocks as big as a house ride along, because the huge glacier keeps creeping forward with far more strength than any rock can hold back.

Far down the mountain, the air is warmer, and the end of the glacier melts away. With no ice left to hold them, the rocks drop right where the ice ends. Some of them sit alone in fields today, far from the mountains they came from.

Let's remember one word, plucking. The glacier's huge weight pulls its ice slowly downhill, and the ice plucks rocks loose from the ground, carries them along, and drops them where it melts.

Isn't it amazing that slow, quiet ice can carry rocks as big as houses? Next time you spot a big lonely rock in a field, you can wonder if a glacier once gave it a ride.