Erosion - When gravity causes water to flow downwards.  As the water flows soil and rocks are moved with it.
   
  Heavy rains and water run-off (water flowing off the land) naturally erode soil.  Humans make erosion happen faster by cutting down trees, removing shrubs and plants, and having too many animals on farmland. 
   
  When soil is lost through erosion, it pollutes rivers, lakes and other water systems.  It also changes the land.  The picture to the left shows a channel that has been formed by flowing water.

The loss of soil can cause plants to become uprooted, meaning they can no longer live.

When soil is lost on farmlands, farmers cannot grow as many crops.  Depleted soil produces crops that provide less nourishment to people.
   
  Erosion effects the human environment by more than affecting our food supply.  When land is eroded it can effect structures as well.  The picture below shows a building being torn down.  The reason it is being torn down is that it was located near a beach, and the sand has slowly been washed away, which caused the building to be unstable (if you want to read more about this, here is the news story).
   
  To try to stop the erosion of land, humans will often put up walls or other barriers to stop the water from touching the soil.  They also use pipes to redirect the water to a place where it will not affect the land as much.  In some cases, like the picture to the right, this helps keep us safe

 

Humans have also taken advantage of the flowing water that causes erosion.  By directing the water they can capture the energy from it to power other things.  This water wheel is being turned by water that has been direct through a man-made channel.

 
   
  Below you will find a video that explains and shows the erosion of mountains in Wyoming.