The Grand Canyon is a place where there is a rock in the middle and then there is a river below it. There is a place that goes below the surface of the earth and it's very deep. Cross-cutting  comes in when the rock comes out of the middle of the earth surface. 

Before there was white and black moths. Now there is black moths only.The reason why is that the pollution changed the color of the trees. So, then the white moths were easier to see on the black trees. Before the black moths were going to be extinct because they landed on white trees which was easier to see. The white moths were the easiest to see on a black tree, so that's the reason why they became extinct.