Ch. 10 &12 Weathering, Erosion, & Deposition

Weathering Is the breakdown of rock into smaller and smaller pieces. 2 types of weathering: Mechanical Weathering: simply the breakdown of rock into smaller pieces by physical means.

Examples of mechanical weathering: Ice wedging Roots growing into cracks to spread more Gravity, water, and wind cause abrasion Activities of plants and animals on rock

Chemical Weathering: chemical breakdown of rocks and minerals into new substances. Agents of chemical weathering: water, weak acids, air, and soil.

Examples of chemical weathering: Water dissolving rocks and minerals. Sulfuric and nitric acids from pollution Natural acids found in air and water Oxidation from oxygen and other metallic elements combining.

Rates of Weathering Differential weathering: process by which softer, less weather resistant rocks wear away. The greater the surface area of a rock, the faster the rate of weathering. Different climates promote different rates of weathering.

Chemical weathering occurs faster in warm, humid climates. Usually occurs at faster rate at higher elevations due to an increase in ice, rain, and wind.

Soil Soil is made up of loose, weathered material that can include organic material called humus. Also includes weathering of bedrock. Residual soils rest on top of their parent rock, and transported soils collect in areas far from their parent rock. Soils usually consists of horizons, layers that are different from one another.

Soils are very important b/c they provide nutrients for plants, homes for animals, and storage for water. Soil fertility- ability of soil to provide nutrients so that plants can survive and grow Soils need to be protected from nutrient depletion and erosion through the use of soil conservation methods. Different climates have different types of soil, depending on temp. and rain fall

Agents of Erosion and Deposition Erosion: breakdown and movement of materials. Deposition: takes place when these materials are dropped. 1. Shoreline: where land and water meet Wind from storms usually produces large waves that cause shoreline erosion. Surf- waves break when they enter shallow water. Beaches are made of the materials deposited by waves.

Beaches Sandbars and spits are depositional features caused by longshore currents. Sea cliffs, sea caves, sea arches, and sea stacks are coastal formations caused by wave erosion. Longshore current cause sand to move in a zigzag pattern along the shore.

2. Wind Is an important agent of erosion and deposition in deserts and along coastlines. Saltation: process of the wind bouncing sand grains downwind along the grain. Deflation: removal of materials by wind. If deflation removes all fine rock materials, a barren surface called desert pavement is formed. Abrasion: grinding and wearing down of rock surfaces by other rock or sand particles.

Dunes: formations caused by wind-deposited sand. Loess: wind-deposited silt and it forms soil material good for farming. 3 formations caused by wind erosion and deposition: desert pavement, deflation hollows, and dune.

3. Ice Glaciers: masses of moving ice 2 types of glaciers: Alpine glacier- form in mountainous areas Continental glacier- spread across entire continents

Alpine glaciers produce rugged landscape features. Glaciers move when the ice that comes into contact with the ground melts and when the ice crystals slip over one another. Alpine glaciers produce rugged landscape features. Ex.- cirques, aretes, horns. Continental glaciers smooth the landscape.

Glacial deposits: Stratified drift: rock material that has been sorted and deposited in layers by water flowing from melting ice Till: unsorted rock material that is deposited directly by ice melting Landforms deposited by glaciers include outwash plains and moraines. Four types of moraines- lateral, medial, ground, and terminal

4. Gravity: causes rocks and soil to move downslope Mass movement: movement of material downhill due to force of gravity Angle of repose: steepest slope at which loose material will remain at rest. Rock falls, landslides, mudflows, and lahars are all types of rapid mass movement. Creep: type of slow mass movement. Water, plants, and burrowing animals can cause creep