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Changing the earth’s relief. Evolution of the landscape. Changing the earth’s relief: mountain formation. Relief = shape of the earth surface Formation of mountains = Orogenesis through convergent tectonic plate movements mountain: - steep slopes
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Changing the earth’s relief Evolution of the landscape
Changing the earth’s 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
? Why are they different? Laurentians Rocky Mountains
Montreal streets : After the winter: worn down
? Why are they different? Laurentians Rocky Mountains ! Laurentians a lot older have been worn down
Weathering • Gradual destruction of rock on the earth surface. • http://www.youtube.com/watch?v=z2nwiba0N0Y
Mechanical weathering The power of water: Rock is fragmented, but not changed in its composition
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
Chemical weathering Minerals in rock are dissolved and changed.
Chemical Weathering • Dissolvingandchangingmineralsin rocks Composition of rock changes. • Through: - washing out of certain minerals enhanced through acid rain
Biological Weathering Living organisms destroy rock.
Biological weathering • Plant roots can break rocks • Living organisms release acids changes and weakens the rock
Practice: what kind of weathering? 2 1 2. Chemical 1. Mechanical 3 3. Mechanical + Chemical
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 !!!
The three stages of Erosion Erosion 1.) Weathering 2.) Transport: water, wind, ice 3.) Deposition: in lake, stream, ocean
Changing the earth’s 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
Effects of erosion • Hole on Sherbrooke May 2012 • Caused by hole in water collecting pipe • What happened?
homework • Worksheet to be collected next class
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.