Weathering is the breakdown of rocks and minerals at the surface of the Earth. There are two types of weathering: mechanical (physical) weathering, which breaks rocks into smaller pieces through forces like freezing and thawing or root growth without chemical change; and chemical weathering, where rocks undergo chemical reactions with substances like water, oxygen, acid rain, or living things that break them down.

1. Weathering What is your definition?

2. Weathering is the breakdown of rocks and minerals on the earth's surface. Many things cause this to happen. There are two types of weathering: Mechanical (physical) Chemical

3. What is mechanical weathering? It is when rocks break down into smaller pieces because of some physical force. The rock does not change chemically, it just gets smaller! Sometimes called PHYSICAL weathering.

4. Photo by A. Criminger Freezing and thawing is breaking these rocks apart! Ice Wedging

5. ice wedging (freezing/thawing)

6. Photo by A. Criminger Ice is breaking these rocks apart

7. Photo by A. Criminger Roots are breaking these rocks apart. ROOT PRY

8. Abrasion

10. Animal action

11. What is chemical weathering? Chemical weathering occurs when rocks are broken down by a chemical reaction. This can happen by water, oxygen, acid rain, and even living things.

12. http://web.mala.bc.ca Water can dissolve rocks. http://www.arts.tas.gov.au

13. http://www.geo.lsa.umich.edu

14. Oxygen reacts with iron and weathers into rust http://www.raisethehammer.org On rocks On man made objects

15. Photo by A. Criminger Sometimes rocks are not the only things that get chemically weathered!

16. Copyright © Bruce Molnia, Terra Photographics Carbon Dioxide Carbon dioxide combines with water and forms a weak acid. This acid, over time can dissolve rock.

17. www.nullarbornet.com.au

18. Photo by A. Criminger This rock is being broken down by the chemicals in the roots of the lichen growing on the rock.

19. plant growth http://www.geo.lsa.umich.edu

20. http://www.cartage.org.lb/ Rates of weathering