1. By Michael Nau and Elizabeth Dorsey

2. Weathering vs. Erosion  Erosion involves movement and weathering does not.  Weathering is the main agent in erosion. http://www.nature.nps.gov/geology/usgsnp s/misc/gweaero.html

3. Weathering  CHEMICAL: involves a chemical change in some of the minerals in the rock  PHYSICAL: when the rock physically brakes down  Weathering makes sediment (fragments of material) which is moved by deposition (wind, water and ice) http://www.nature.nps.gov/geology/usgsnp s/misc/gweaero.html

4. Erosion  When forces of nature move soil and rock  SHEET EROSION: when rain washes away top soil on sloped land. Gravity (the force that pulls stuff down) is the force that makes eroded material slide down hill  Erosion from the Colorado River formed the Grand Cannyon. http://www.watersheds.org/earth/erosion.ht m

5. Rock Cycle  ROCK CYCLE: a model of the formation, breakdown and reformation of rocks  Igneous rocks form by cooling magma  Metamorphic rocks form from heat and pressure  Sedimentary rocks form by sediment being compacted into layers (may contain fossils, skeletons of dead plants/animals) http://www.answers.com/topic/sediment

6. Different parts of the Earth were once under the ocean  For example, if you found a shark tooth on a hill, you could assume the hill was once underwater. http://www.nature.nps.gov/geology/usgsnp s/misc/gweaero.html

7. Laws and Scales  The Law of Superposition says that sedimentary layers form with the oldest layers on the bottom and newest on the top.  The Geological Time Scale shows the different periods the Earth went through. http://www.enchantedlearning.com/subject s/Geologictime.html