1. Weathering Section 10-1 2/22/16

2. What is Weathering?  Breakdown of rock into smaller and smaller pieces  Occurs at Earth’s surface  Two main types:  Mechanical  Chemical

3. Mechanical Weathering  Breakdown of rock by physical means  Several agents (causes) of mw:  Ice  Wind  Water  Gravity  Plants & Animals

4. Ice Wedging  Water seeps into rocks, freezes into ice and expands  cracks form in rock  Ice melts and travels further into rock, freezes and expands  bigger cracks  Cycle repeats until rock finally breaks apart

5. Types of Abrasion  Action of rocks and sediments grinding against each other and wearing away exposed surfaces Water Wind Gravity

6. Plant Weathering  Small roots enter cracks in rock searching for nutrients  Roots gets bigger  cracks get bigger  rock breaks apart  Look at the sidewalk as you walk home today

7. Animal Weathering  Animals that burrow such as worms, ants, mice, rabbits, etc. affect weathering in two ways:  Burrowing breaks rocks into smaller pieces  Burrowing exposes buried rocks to weathering at surface

8. Chemical Weathering  Breakdown of rock by chemical means  Changes composition of rock  Agents of CW:  Water  Air  Acids  Water and living things

9. Water  Over time has ability to dissolve substances  Think salt or sugar  Able to break bonds in minerals  rock breaks apart  Takes a very long time

10. Three Types of Acids  Acid Precipitation: formed by certain gases mixing with water in the atmosphere  Sources of gases include volcanoes and fossil fuels  Acids in Groundwater: similar to A.P. in that acids get into water that travels underground  Can result in cave formation over several years  Acids from Living Things: Organisms such as lichens produce acids to break down rocks into nutrients for use in life processes

11. Acid Examples

12. Air  Oxidation: reaction between oxygen in the air and certain metals  Rust is an example  Metals in rocks are chemically changed and become weaker  rock is easier to break apart