Where  do you think mountains come from? Why are some rocks smooth and others very  rough? What is an earthquake? In this video, we answer all sorts of questions  about changes in the Earth's surface. Earth's surface or crust is constantly  changing. Some changes happen very quickly, like a volcano or earthquakes.  Others, like weathering and erosion, take thousands of years to make a  change. Join us to learn more about our ever-changing Earth!