Presentation on theme: "Weathering, Erosion, and Soil"— Presentation transcript:
1Weathering, Erosion, and Soil What type of rock is this, how can you tell?
2Yosemite Valley, California Mountains Carved by Glaciers
3Grand Canyon, ArizonaCarved out by the Colorado River
4Bryce Canyon, Utah Acidic Rainfall has worn away these rocks. The harder rocks remain standing… but for how long?
5Weathering The 2 G’s and the 3 W’s Process by which rocks are broken down due to exposure to processes occurring at the Earth’s surfaceCaused byWaterWavesWindGravityGlaciersThe 2 G’s and the 3 W’s
62 Types of WeatheringA. Mechanical Weathering also called Physical weatheringRock is broken down into smaller pieces of the same material(no change in composition)B. Chemical WeatheringThe breakdown or decomposition of rock that occurs when minerals are changed into different substances(change in composition)
7Mechanical/Physical Weathering Frost (Ice) WedgingProcess in which water freezes in the cracks of rock and wedges (pushes) it apart because water expands when it freezes.Occurs where there are frequent freezes and thaws.
17O2 Chemical Weathering Chemical Weathering The breakdown or decomposition of rock that occurs when minerals are changed into different substances(change in composition)Involves Water ,water vapor, Acids, and/or OxygenO2
18Chemical Weathering Hydrolysis Carbonic Acid in water dissolves Calcite. This chemical weathering can hollow out underground CavernsLimestone and Dolomite both dissolve because they contain Calcite
19Acid rain (carbonic acid) weathering the details of statues and tombstones Ex: Marble and Limestone
20Chemical Weathering Oxidation This is why Mars is the red planet Oxidation of minerals with iron (magnetite, pyrite) results in the formation of rust or iron oxide.This is why Mars is the red planetCopper turns rocks green
21Rate of Weathering Surface area Rock composition Climate How fast a rock weathers depends on 3 factors:Surface areaRock compositionClimate
22Rate of Weathering Surface area The greater the surface area, the faster the weathering rateThere are more surfaces to be weathered
23Rate of Weathering Rock composition Some minerals are more resistant than othersFor example, quartz is more resistant (harder) than calciteQuartzCalcite
24Rate of Weathering Climate (long term pattern of moisture and temperature)Weathering rates are faster in warm, wet climatesDesert vs. Rainforest
25ErosionErosionThe removal and transport of weathered materials by natural agents such asCaused byGlaciersRunning waterGravityWindWaves
26GlaciersMass of compacted ice and snow that moves under its own weight
27GlaciersFriction at the base of the glacier is reduced by a thin film of melt water.Glaciers account for about 75% of the fresh water on Earth
28Glaciers can leave behind large boulders that are known as an erratic
29GlaciersGlaciers can move lots of sediment that can carve striations (grooves) into rocksThese Striations show how glaciers moved
30Glacial DepositsDrift or Till - all sediment that is deposited by glacial activityLoess: fine powder, pulverized rock, that blankets much of the northern mid-westMoraine: ridge or pile of boulders, gravel, sand, and silt left at the end of a glacierEsker: type of outwash that accumulates in the channels and tunnels of a glacier
31Glacial LandformsHorne: a pyramid shaped peak where 3 or more cirques meetCirqueSteep-walled bowl-shaped depression
32Glacial Landforms Trough U-shaped valley, Glaciers carve U shaped valleys
33Glacial Landforms Arete Hanging valley Narrow flat-topped ridge that forms between two parallel troughs or cirquesHanging valleyStraight drop-off at the end of a trough
34Glacial LandformsMoraine: Pile of mixed sediments that have been carried and dropped by the glacier
35Glacial LandformsEskers -Mounds of rock from melt tunnels
37Streams and Rivers Velocity - How fast the water moves Gradient - The steepness, the slope that a river or stream travelsDischarge - The amount of water that moves past a certain point in a river in a given amount of timeIf there is a steep gradient, high velocity, and a large discharge, then Erosion will be severe!Rivers have energy to move lots of sediment, and even large boulders.
38River stages affect: Velocity, Gradient, & discharge which cause Erosion
40Seven Bends of the Shenandoah River meandersBends in the river, shows how mature a river is.Is the Shenandoah and old river or a young river?
41Erosion-Mass Movement The downward transportation of weathered materials by gravityMassive Landslide
42Erosion-Mass Movement CreepSlumpMudflow/EarthflowLandslide/Rockslide
43Erosion-Mass Movement: A large mass of sediment drops down!
44Erosion-Mass Movement CreepVery slow movement of earth material.Caused by repeated freezing and thawing.Sediments are loosened by expanding frost and contracting thaw.Leaning fence posts and telephone poles are a sign of Creep.
48Erosion-Mass Movement Mudflow/EarthflowThick pastes of sediments that travel downhill at great speedsUsually occur in dry areas that get a large quantity of rain all at onceLeaves a cone shaped deposit
49Mudflow in the Blue Ridge Mooreman’s Gap near Charlottesville
50Erosion-Mass Movement Landslide/RockslideFast movement of large blocks of rockOccurs in very steep vertical cliffsAccelerated by ice wedging
61Where soil forms Residual soil Transported soil The parent rock is the bedrock beneath the soil (the soil has not moved)Transported soilSoil forms from parent material left by winds, rivers, glaciers, or soil that was moved from its original location. This soil has been transported by erosion and deposition
62Factors that affect Soil Composition Parent material: What bedrock is it from?Time: How long has it had to decompose?Plants and animals: How have roots and animals helped break up the rocks? Were there acid producing mosses that help break down the rocks (chemical weathering)?Topography: What is the shape of the landscape?Climate: Is it warm & wet? Were there glaciers present? Was there acid rain?
63Soil ProfileCross section of soil layers revealing all soil horizons
64Soil HorizonA soil layer with physical and chemical properties that are different from adjacent layersO Horizon= organic material (humus)A Horizon = topsoilB Horizon = subsoilC Horizon = partially weathered parent material
65Idealized Soil Profile Humus:Dark organic matter in soil that is rich in nutrients.
66Leaching: The removal of nutrients or toxins in soil as water passes through the layers.