Again, the harder the layer, the slower the process. So we get areas like the grand canyon where the river has always traveled the path of least resistance and broken down the weaker rocks first. Some rocks are harder than others. However nothing I personally can do will break apart granite unless I get help from a hammer or other device. This varying hardness means that wind and other forces such as water, wear through some kinds of rock faster than others.
Granite is an igneous rock that cools deep inside a volcano rather that erupting out.
Sand then may be carried off by rivers, glaciers, or winds. Relate Activity and Concept Students can take turns examining the large grains with the magnifying glass. Compare the grains with the minerals that comprise granite. Connect to Everyday Examples Ask students about the Grand Canyon - as an example of erosion. Language Arts Connection Tell students that they are to solve a fictional mystery for the future city of Chicago.