1. Weathering
The breaking down and changing of rocks at or near the Earth’s surface
2 Types:
Mechanical
Chemical

2. Mechanical Weathering
Occurs when physical forces break rock into smaller and smaller pieces without changing the rock’s mineral composition
Mechanical weathering increases surface area

3. Three processes that cause mechanical weathering
Frost Wedging
caused by the expansion of freezing water in cracks and crevices.
wedged loose rocks may tumble into large piles called talus, found at the bases of steep, rocky cliffs

4. Three processes that cause mechanical weathering
2. Unloading/Exfoliation
Reduced pressure on igneous rock causes it to expand and allows slabs of outer rock to break off in layers in a process called exfoliation

5. Three processes that cause mechanical weathering
3. Biological Activity
The activity of organisms, including plants, burrowing animals, and humans

6. Chemical Weathering
Is the transformation of rock into one or more new compounds

7. Processes of chemical weathering
Water (dissolved gases)
oxygen (Fe + O2 = rust!)
CO2 (carbonic acid)
sulfur/nitrogen oxides (acid rain)

8. Erosion
Erosion – major external process: loosened material is dissolved, or worn away from one part of the Earth's surface and deposited in another
Streams – the most important agent of erosion
produce ordinary valleys and canyons; may form deltas when they flow into lakes and oceans
Wind Erosion – produces dunes or loess
Human activities can accelerate erosion: activities that destroy vegetation