Term
| How does weathering differ from erosion? |
|
Definition
| Weathering is the mechanical and chemical alteration of earth materials at or near the surface, whereas erosion involves removing weathered materials from their place of origin by running water or wind. |
|
|
Term
| What accounts for differential wethering and erosion, and what are their effects? |
|
Definition
| Weathering and erosion take place at different rates evven on the same body of rock. They are not compositionally and structurally homogeneous throughout thereby producing uneven surfaces. |
|
|
Term
| How do freezing and thawing contribute to weathering? |
|
Definition
| When water freezes in cracks in rocks it expands and then it contracts when it thaws. This exerts pressure and opens the cracks wider. Repeated freezing and thawing diagregates rocks into angular pieces that may tumble downslope and accumulate as talus. |
|
|
Term
| What are sheet joints and how do they form? |
|
Definition
| Sheet joints are fractures that more or less parallel exposed rock surfaces, especially rocks now at the surface that formed under great pressure at depth. These joints form in response to pressure release; that is, when the rocks formed, they contained energy that is realesed by outward expansion. |
|
|
Term
| How do organisms contribute to mechanical and chemical weathering? |
|
Definition
| Any organic activity such as tree roots growing in cracks contributes to mechanical weathering, whereas organic acids and the tendrils of mosses and lichens aid in the chemical alteration of parent material. |
|
|
Term
| What happens to rock composed of carbonate minerals when they are exposed to acidic solutions? |
|
Definition
| Rocks such as limestone (CaCO3) are nearly insoluble in neutral or alkaline solutions, but they rapidly dissolve in acidic solutions b/c the atoms making up the minerals separate and the rock dissolves. |
|
|
Term
| What takes place when potassium feldspars undergo hydrolysis? |
|
Definition
| During hydrolysis hydrogen ions react with and replace positive ions in potassium feldspar, yielding clay minerals and substances in solutions such as potassium and silica. |
|
|
