Weathering & Erosion

1. Weathering & Erosion The five forces that drive erosion

2. 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.

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

4. The answer is billions of years of time and erosion

5. 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.

7. Erosion by water • Erosion by water can take the form of waves, the flow of rivers, as well as rainfall events. • Since 1 m3 of water weighs 1 metric tonne, the movement of water has important erosive capabilities.

9. Erosion by Ice • Ice causes erosion in two ways; • Glaciers are flowing rivers of ice that remove enormous amounts of soil and rock and deposit them great distances from their place of origin. • Frost heave occurs when water in a soil or in the cracks in rocks freezes and expands, this results in the slow breakdown of the soil or rock.

11. Erosion by Temperature • Changes in temperature cause rocks to expand as they are heated and to contract as they are cooled. • These changes are very small but over 100s and 1 000s of years they can cause the rock to break apart.

13. Erosion by Wind • A strong wind will pick up sand and even rock particles and crash them into other objects • which are worn away over time. This is a similar effect to sandblasting.

15. Erosion by Plants • Plant roots grow into the cracks in rocks and slowly force the rock apart.