11.+External+Forces+Shaping+the+Earth

=Weathering and Erosion= These are two forces responsible for changing the surface of the earth. They can work quickly or slowly. We see them both at work all the time. Keeping up with them to prevent their respective changes can be quite a challenge. In a period of a few years they can noticeably alter a place. See the story about the [|Old Man of the Mountain].

Read and take notes from: pp. 42-45 of //World Geography//

Copy the chart below into your notebook, and complete it.


 * **Cause** || **Effect** ||
 * || Sediment ||
 * || Erosion ||
 * || A delta ||
 * || Varying types of soil ||

Watch and take notes from the following mini-lectures, and cartoon.

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 * Chemical Weathering**

Carbonation
This process speeds up with a decrease in temperature and therefore is a large feature of glacial weathering as carbon dioxide is more soluble at lower as opposed to higher temperatures. The reactions as follows: ||
 * Carbonation is the process in which atmospheric carbon dioxide leads to solution weathering. Carbonation occurs on rocks which contain calcium carbonate such as limestone and chalk. Carbonation takes place when rain combines with carbon dioxide to form a weak carbonic acid which reacts with calcium carbonate (the limestone) and forms calcium bicarbonate.


 * CO2 || + || H2O || -> || H2CO3 ||
 * carbon dioxide || + || water || -> || carbonic acid ||
 * H2CO3 || + || CaCO3 || -> || Ca(HCO3)2 ||
 * carbonic acid || + || calcium carbonate || -> || calcium bicarbonate ||
 * carbonic acid || + || calcium carbonate || -> || calcium bicarbonate ||


 * Adapted from Wikipedia ||




 * ==Oxidation== ||

This process is better known as 'rusting'. || Adapted from Wikipedia
 * Within the weathering environment chemical oxidation of a variety of metals occurs. The most commonly observed is the oxidation of Fe2+ (iron) and combination with oxygen and water to form Fe3+ hydroxides and oxides such as goethite, limonite, and hematite. This gives the affected rocks a reddish-brown coloration on the surface which crumbles easily and weakens the rock.


 * Assignment: [[file:Weathering and Erosion.pages]]**