Layers of the Earth

     Over time, humans have changed the Earths Crust. In the early 1900's, people had just invented cars and were starting to pollute the air. By building cars, they had to build roads to drive on, which changed the Crust. 
     Another way they polluted the air was when they started building factories, and Power Plants. People dug holes for basements in new houses. Building sidewalks, roads, houses,  and factories, people are changing the Crust.

At this very moment, people are changing the Crust all over the world! There are even some things that change the Crust that aren't caused by humans, such as, hurricanes, tornados, floods, earthquakes, tsumamis, and typhoons.