Weathering & Erosion

1. Weathering & Erosion The five forces that drive erosion

2. I can… • Identify and describe the 5 forces that drive erosion. • Develop a sense for the power of the forces of erosion.

3. Introduction (pt I) • 3, 500 million years Before Present (B.P.). • Cracks in the earth's crust release magma from thousands of volcanoes which form the Canadian, Australian, African, and Asian Shields.

4. Introduction (pt II) • Since the early Canadian Shield was as high as the Himalaya, how did we get from the Himalaya to Mt Pakenham?

5. The answer is billions of years and erosion 9 1 5 6 8 10 7 2 4 3

6. Weathering & Erosion(definitions) • Weathering is the breakdown of rock into small particles. • Erosion is the wearing away of the earth’s surface followed by the movement to other locations of the materials that have worn away.

8. Erosion by water • Erosion by water is caused by waves, rivers, and rain. • A box of water 1 m3 weighs 1 metric tonne, giving water its erosion power.

11. Erosion by Ice • Ice causes erosion in two ways; • Glaciers are rivers of ice that move huge amounts of soil and rock, and drop them far from their place of origin. • Frost heave happens when ice forms and cracks rocks open, this slowly breaks the rock apart.

14. Erosion by Temperature • Changes in temperature cause rocks to expand when heated and to shrink when cooled. • After thousands of these changes the rock will break apart.

17. Erosion by Wind • Wind will pick up sand and crash it into other objects which are worn down over time. • This is a similar effect to sandblasting.

21. Erosion by Plants • Plant roots grow into the cracks in rocks and slowly force the rock apart, wearing it down.