Forces of Change : Destructive Forces 1 Forces of Change : Destructive Forces Forces that wear away the Earth are destructive forces.

There are two types of destructive forces. (Earth’s Surface text) 2 There are two types of destructive forces. (Earth’s Surface text) A. Weathering (p.115-120) B. Erosion

I Destructive Forces A. Weathering: 3 I Destructive Forces A. Weathering: The breaking up of rock without removal of the pieces.

1. Mechanical 4 The physical breaking up of rock without chemically changing it into a new substance.

1. Mechanical a.)plant action; 5 a.)plant action; When the the root hairs of a plant grow into the pores of a rock. As the root grows , it expands and breaks the rock.

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1. Mechanical b.)frost action(Ice wedging); 7 b.)frost action(Ice wedging); When water seeps into the pores of rock during the day and freezes at night.The frozen water expands and over time breaks the rock.

8 www.trp.dundee.ac.uk/~spitz/misc.html

1. Mechanical c.) temperature change; 9 c.) temperature change; When a rock is heated during the day, it expands and at night, as it cools , it contracts. Over time this process breaks the rock.

10 Also called thermal expansion.

Abrasion (p.116) 11 wears away exposed rock http://www.ergis.cz/krkonose/index.php?lang=en&menu=1&navid= 170&search_filter=category=-4-%3Bsearch=true

Pressure release (exfoliation p116) 12 Exfoliation is the process of the rock breaking off in layers http://en.wikipedia.org/wiki/File:GeologicalExfoliationOfGraniteRock.jpg

2. Chemical 13 The breaking up of rock by chemically changing the elements that make it up into whole, new but weaker elements. This causes the rock to crumble.

2. Chemical a.) oxidation; 14 a.) oxidation; When an element or compound in a rock combines with oxygen. Most elements that oxidize become weaker.If any of the elements in the rock combine with oxygen, the rock breaks apart.

15 www.geographyjim.org/weathering.htm www.americanbonanza.com/.../ photo_gallery/

2. Chemical b.)compounds in water; 16 b.)compounds in water; Minerals combine with water to form new compounds. These compounds expand over time causing the rock to break.

2. Chemical c.)carbonation; 17 c.)carbonation; When carbon dioxide from the atmosphere dissolves in water, it creates carbonic acid. This acid removes the minerals in the rock and forms new compounds called carbonates.

18 Carbonic acid from acid rain has dissolved some of the limestone www.geographypages.co.uk/limgran.htm 18 Carbonic acid from acid rain has dissolved some of the limestone and left cracks.

The breaking up of rock with removal of the pieces. 19 B. Erosion:(p. 142 - 170) The breaking up of rock with removal of the pieces.

B. Erosion There are four agents of erosion; 1. Gravity (p. 147 - 149) 20 There are four agents of erosion; 1. Gravity (p. 147 - 149) 2. Water (p. 150 - 161) 3. Wind (p.161 - 163) 4. Moving ice (p. 165 - 170)

1. Rockfall-an individual rock slides downhill. GRAVITY 21 A)Mass wasting 1. Rockfall-an individual rock slides downhill. 2. Rockslide -many rocks slide together downhill. 3. Mudflow- debris mixed with water moves downhill. 4. Slump- a slide of loose debris that moves as a single unit. 5. Creep - mass of soil and rock move 1 -10 mm per year.

Rockfall 22 http://atlas.nrcan.gc.ca/site/english/maps/environment/ naturalhazards/landslides/fig_2_land_rockfall.jpg/image_view

Rockslide 23 http://www.cbc.ca/canada/story/2008/08/01/f-newsweek.html

24 F L O W M U D

Slump 25 http://www.geosci.usyd.edu.au/users/prey/ACSGT/EReports/eR. 2003/GroupD/Report2/web%20pages/Listric_Faults.html

CREEP Creep 26

B. Erosion 27 2. Water erosion a.) mechanical 1.) running water carries particles of sand ,pebbles rocks and even boulders that wear away the surfaces that they come into contact with. This type of water erosion does not change the chemical make up of any of the particles.

Mechanical Water Erosion 28 Water erosion creates different land forms (p. 150 - 163). Streams - small or large run downhill in a channel. Drainage basins - area of land in which water drains into a stream and eventually into a lake or ocean. Divide - A ridge from which water drains from one side or the other.

Locate the divides. 29 These streams drain an area called the drainage basin. Locate the divides. 29 http://www.kidsgeo.com/geology-for-kids/0076-drainage-basins- watersheds.php

Mechanical Water Erosion 30 Water erosion creates different land forms. Valleys and canyons - p.152 V shaped in high mountains where water runs swiftly and cuts deep. Wide valleys in low, flat land where water runs more slowly and flood waters deposit silt creating large flood plains.

31 http://www.evans-politics.com/yellowstone.html

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Mechanical Water Erosion 33 Water erosion creates different land forms. Meanders p. 152- as streams or rivers enter flat land, they slow and begin to curve causing sediment to be dropped on the inside bank and eroding the outside bank. Oxbow lakes p. 152 - During a flood the meanders may cut a new path and cut off a meander leaving it As a U-shaped body of water.

34 "Image courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center." 34 Astronaut Photography of Earth - Display Record ISS015-E-6477

Mechanical Water Erosion 35 Water erosion creates different land forms. Alluvial fans p. 153- when water leaves sediment at the base of a mountain as it enters open space, it drops the sediment in a fan shaped feature. Delta p. 153 - when water leaves sediment at the mouth of a river as it enters open water such as an ocean, it drops the sediment in a fan shaped feature.

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http://www.earthdesign.com/biahyperspectral/skokomish_delta.jpg 37

B. Erosion 38 2. Water; b.) chemical- p. 154 1.) running water that has carbonic acid in it will take away the calcium (calcite) in the surfaces that it comes into contact with and wash it away. This is how most caves are formed.

Chemical Water Erosion 39 Water erosion creates different land forms. Caverns p. 154- Caused by acidic water seeping into the ground and reaching the bedrock. This water can erode limestone within the rock and create huge caves called caverns. Sinkholes p. 155 - are formed when the top of a cavern has caved in.

http://skywalker.cochise.edu/wellerr/students/colossal-cave/cave.htm 40

41 http://studentloancenter.com/blog/index.php?entryid=225

Waves 42 Waves and currents shape shorelines p.158- 159 Longshore drift- the zigzag motion of sand along a beach causes the beach to erode in one area and be built up in others. Longshore current - the movement of water along a shore. Usually, this movement is at an angel and the angel changes depending on the direction of the waves. This erodes beaches.

Waves 43 Waves and currents shape shorelines p.160 Sandbars - a ridge of sand built up under water by the action of currents and waves. barrier island - a ridge of sand built up above water by the action of currents and

44 http://www.australiaadventures.com/pictures.htm

45 http://geology.rockbandit.net/2008/09/15/how-barrier-islands-such-as-galveston- work/

B. Erosion 46 1.Wind; When wind storms blow sand and dust at other rocks , the particles wear away the rocks or other surfaces that they hit. Other particles break off and they too are carried by the wind to other places. Wind erosion forms; 161 -163 Dunes Loess deposits Desert pavement

47 http://projects.math.arizona.edu/~sp2007/sdgroup.html

48 http://www.pbase.com/dougsherman/image/94997414

49 http://z.about.com/d/geology/1/0/q/O/1/paveblythecloseup.jpg

B. Erosion Moving ice; p. 165 - 170 moraines. 50 is called a glacier. A glacier can carve deep, wide valleys and move huge amounts of land to other places. Glaciers deposits are called till. Types of till include; moraines. drumlins kettle lakes.

Alpine Glacial valley 51

52 http://formontana.net/moraine.html Postcard Photo by Lawrence Dodge of Big Sky Magic Enterprises

53 http://oz.plymouth.edu/~sci_ed/Turski/Courses/Earth_Science/ Images/4.drumlin.jpg

54 http://www.physicalgeography.net/fundamentals/10af.html