Mr. Garcia: Today we're starting our unit on erosion, and I want to begin with a place right here in Texas: Palo Duro Canyon, in the Texas Panhandle. Palo Duro is one of the largest canyons in the United States. Some people call it the Grand Canyon of Texas.

Mr. Garcia: So how does a canyon this big form? The answer is water and a very long time. A river runs along the bottom of Palo Duro Canyon. Over a very long time, the moving water carried away tiny pieces of rock and soil, a little bit at a time. Wind and rain helped, too. That process of wearing away rock and soil and carrying it somewhere else is called erosion.

Mr. Garcia: If you ever visit, look at the canyon walls. You'll see stripes of different colors: red, orange, yellow, and white. Each stripe is a layer of rock that formed at a different time. The layers at the bottom are the oldest, and the layers near the top are younger. So you could say the walls are like a history book, and the river opened it up for us to read.

Mr. Garcia: Tomorrow we'll go outside, build a hill out of sand and soil, and pour water over it to watch a tiny version of this happen.