Slide 1

Changing the earths relief Evolution of the landscape Textbook p. 314, 333-335 Slide 2 Changing the earths relief: mountain formation Relief = shape of the earth surface Formation of mountains = Orogenesis through convergent tectonic plate movements mountain: - steep slopes - at least 600m high Mountains in the making: Himalaya, Rocky mountains, Alps Slide 3 Laurentians Rocky Mountains Why are they different? ? Slide 4 Montreal streets : After the winter: worn down Slide 5 Laurentians Rocky Mountains Laurentians a lot older have been worn down ! Why are they different? ? Slide 6 Weathering Gradual destruction of rock on the earth surface. http://www.youtube.com/watch?v=z2nwiba0 N0Y http://www.youtube.com/watch?v=z2nwiba0 N0Y Slide 7 Mechanical weathering The power of water: Rock is fragmented, but not changed in its composition Slide 8 Mechanical weathering Fragmentation of rock through: - Variations in temperature and pressure - water example: freeze thaw cycle of water -wind Composition of rock does not change Slide 9 Minerals in rock are dissolved and changed. Chemical weathering Slide 10 Chemical Weathering Dissolving and changing minerals in rocks Composition of rock changes. Through: - washing out of certain minerals enhanced through acid rain Slide 11 Biological Weathering Living organisms destroy rock. Slide 12 Biological weathering Plant roots can break rocks Living organisms release acids changes and weakens the rock Slide 13 Practice: what kind of weathering? 1. Mechanical 2. Chemical 3. Mechanical + Chemical 1 2 3 Slide 14 Slide 15 Water erosion Slide 16 Glacial erosion Slide 17 Wind erosion Slide 18 Erosion of soil Soil Erosion rates on farmed land between 17 and 40 tons per ha and year average natural soil production only 1 ton per ha and year !!! Slide 19 Journeys end: Deposition Slide 20 The three stages of Erosion Erosion 1.) Weathering 2.) Transport: water, wind, ice 3.) Deposition: in lake, stream, ocean Slide 21 Changing the earths relief: Erosion Erosion is the gradual wearing away (destruction and /or removal) of land surface material, for example rock or soil. Three step process: Weathering of rock (destruction of rock) Transportation of soil and rock debris (through water, wind, glaciers). Deposition of material at another location Slide 22 View from the mountain: Slide 23 Montral Slide 24 Slide 25 Effects of erosion Hole on Sherbrooke May 2012 Caused by hole in water collecting pipe What happened? Slide 26 homework Worksheet to be collected next class Slide 27 Categories of Weathering / Erosion Mechanical Weathering Composition of rock does not change Through: - Variations in temperature and pressure example: freeze thaw cycle of water - Wind and water Chemical Weathering Composition of rock changes Through: - washing out of certain minerals enhanced through acid rain Biological Weathering Living organisms release acids change + weaken the rock Plant roots can break rocks.