| A | B |
|---|
| weathering | The process that breaks down rocks and other substances at Earth's surface. |
| gravity | The force that moves rock and other materials downhill. |
| landslides | Common where road builders have cut highways through hills or mountains. |
| creep | A slow movement of rock and soil you barely notice. Objects may be tilted at spooky angles. |
| slump | The material moves down in one large mass. Occurs when water soaks the base of a mass of soil that is rich in clay. |
| mudflows | Rapid downhill movement of a mixture of water, rock and soil. Occur often after a heavy rain in a normally dry area. |
| frost action | When water freezes in a crack in a rock and it expands and makes the crack bigger. |
| abrasion | When wind, water, or other forces carry particles that wear away rocks. This usually produces small particles and sand. |
| exfoliation | Caused by changes in temperature. It is the breaking off of a material in curved sheets or slabs parallel to its surface. |
| carbonation | When carbon dioxide is dissolved in rainwater and that water sinks through air pockets in the soil. It weathers limestone and marble. |
| oxidation | The product is rust. |
| acid rain | Burning of fuels pollutes the air with compounds that react chemically with water vapor in clouds, forming acids. |
| plant acids | As roots grow, they produce weak acids that slowly dissolve rock around the roots. |
