The most amazing thing we saw this week were the many stone formations in Canyonlands National Park. It's hard to imagine how they form.

In order to understand how the arches form, you have to go back millions of years. Millions of years ago, this area was totally covered by an ocean. There was a lot of sand on the ocean floor.

Then the ocean dried up. The whole area was covered by a few streams. The sand from the ocean floor was still there.

By a couple of million years later, the streams all dried up. The area was covered with sand dunes.

As time passed, different layers of ground were forming. Each one piled on top of the others. Over time, the layers turned into rock. The interesting thing is that each layer created a different type of rock.

As the rock layers erode, sometimes softer layers are under harder layers. The soft layer erodes away and leaves the hard layer above.