External Processes Erosion Weathering

Weathering Weathering - forces that are changing rocks and land over time, even day to day.

Mechanical Weathering Mechanical weathering – when a force breaks a rock into smaller pieces by forcing them apart. Breaking large rocks into smaller ones

Causes of Mechanical Weathering Roots growing through rocks - root wedging ice get into rocks – frost wedging Thermal expansion

Effects of Mechanical Weathering Stone Mountain, GA Grand Canyon

Chemical Weathering Chemical weathering - when something "eats away" at a rock rather than breaking it apart. Must have a chemical change in the rocks

Causes of Chemical Weathering 1. Acid Rain

Regions Sensitive to Acid Rain

Causes of Chemical Weathering 2. Water – creates a chemical reaction in certain rocks 3. Chemicals – resulting from pollution or internal processes Foaming pollution on rocks.

Effects of Chemical Weathering At PH1, this New Zealand lake is pure hydrochloric acid Naked trees Rust

Analysis What is the key difference between mechanical and chemical weathering? Create a weathering wonderland. Sketch a landscape that includes examples of weathering resulting from each of the 6 causes. (3 mechanical, 3 chemical) Label each cause

Rocks that have split apart due to thermal expansion.

Erosion Erosion - the removal of ground materials (soil, sand, rocks) by water or wind.

Glaciers – how they form

Erosion 1. Glaciers  a large, slowly moving, river of ice

Example: Iceland - Glaciers are very powerful. - They carve out huge chunks of land forming canyons and valleys thus creating mountains out of flat land.

Effects of Glaciers Appalachian Mountains - Old Alaska - New

Receding Glaciers Explain this map of Glacier Bay in Alaska. What does it suggest?

Effects of Receding Glaciers 1. What does this graph suggest? 2. What types of decisions might a geographer make based on this data?

Wind Erosion Wind blows the small particles exposing the larger rocks below and smoothing them down.

Wind Erosion – check this out http://www.indiana.edu/~g103/G103/Week8/desert.mov