Chapter 9 Weathering and Erosion Workbook p. 181-200

Weathering As long as bedrock stays underground, it will basically remain unchanged Once a rock outcrop is exposed to the surface, it will go through changes It will WEATHER To break down Two types of weathering: Chemical and Physical Weathering

Chemical vs. Physical Chemical To break down into another form More common in hot, wet areas Examples: Rust, Limestone caves and acid rain, “burning paper” Physical To break down into a smaller version of the same form More common in cool, dry areas Examples: Frost Action, Plants, Soil formation “tearing paper” See p. 96, Figure 4-3

Factors that Affect Rate and Type of Weathering Exposure Closer to Earth’s surface, the faster it will weather Longer the time of exposure, the more weathering that will occur Particle Size The smaller the pieces, the faster the weathering Ice block vs Crushed Ice Mineral Composition Harder minerals are harder to weather Climate Chemical weathering = warm and moist climates Frost action = moist climate that has a repeating freezing-thawing cycle

Soil Formation Weathered rock, microorganisms, and organic remains (i.e.-poop, dead things) NOT dirt Dirt is only weathered rock Covers bedrock in layers, called horizons Bedrock is solid layer of rock beneath soil and dirt Most important layer is the humus Also called topsoil Most important layer Contains THE MOST organic remains Considered rich Must be protected It can take 100’s of years to produce 1cm of topsoil See p. 185, Figure 9-5

Weathering vs. Erosion Weathering To break down Materials stay where they are Erosion To move sediments away Materials are weathered first, then eroded Weathered sediments are deposited in a different location Force of gravity drives most forms of erosion There are 5 agents of erosion…

Open your workbook to p. 186 (1-10) 1 (#2 is erosion, not weathering) 2 4

1- Erosion by Gravity Alone Also known as mass movement Avalanche, landslide, slow creep, mudslide Rocks can fall off of a cliff Rocks off of a cliff will be smooth on one side and rough on the other Unsorted rocks

2- Erosion by Wind Occurs in areas with little to no plant life Causes rocks to be pitted on one side Sandblasting Very angular (pointy) Moves sand dunes from wind side to non-wind side Up with a slope (wind side) Down steep (non-wind side)

3- Erosion by Water Rivers erosion is the most common form of erosion Velocity is caused by 3 things Discharge amount Slope Size of river ESRT p. _ The bigger the velocity of the water, the larger the particle it can move Causes V-shaped valleys riVer

Meandering Rivers Rivers slow because of a meander Water moves fastest on the outside of a bend and slowest on the inside of a bend Fast = Erosion Slow = Deposition

4- Erosion by Waves and Current

5- Erosion by Ice Glaciers are slow moving, massive blocks of ice Glaciers form parallel grooves in the bedrock from dragging things In between the grooves, the bedrock is polished Glaciers form U-shaped valleys

Other Erosional Facts Erosion by Living Organisms Living things (humans for example) dig up the Earth and move it all of the time Humans cause THE MOST amount of erosion in the world Deforrestation Animals dig burrows Plants’ roots break up the ground Mass Movements Slides, flows, and falls Caused by unstable conditions in slope materials