NOTES: Processes of Change 
 
Two main processes that change the Earth’s surface: weathering & erosion 
 
Weathering: slow wearing-away or breaking down of objects exposed to Earth’s atmosphere & water 
-Mechanical weathering: objects are broken into small pieces but the chemical composition of the object does not change. 
-example: the sphinx 
-changes in temperature cause objects to expand/contract, causing cracks 
-Chemical weathering: when an objects chemical makeup changes due to chemicals in the atmosphere 
-example: metal rusts when left outside because water and causes an oxidization reaction 
-chemicals released into the atmosphere condense into clouds and fall back to Earth as acid rain, which causes metal to change color and rock to be destroyed. 
Example: The Statue of Liberty is copper but has turned green from the acid rain reacting with the copper 
 
Erosion: moving of materials from one place to another by nature 
-example: Grand Canyon (where river used to flow is now a canyon b/c the rushing water carried pieces of rock away) 
-landslide: mud, rock, or dirt is pulled down a hill by gravity 
-Deposition: the building up of land by erosion 
-example: sand dunes are built up when wind carries the sand to a new location 
-Erosion can occur by rain, wind, gravity, glaciers, waves, water, hurricanes, etc.