Surface Processes on the Earth Rocks, Weathering, Erosion and Soil
ROCKS AND ROCK CYCLE
Rock types Three main types of rock Igneous Metamorphic Sedimentary
Igneous Form when magma or lava cools and hardens Found in the upper mantle and lower crust
Classifying Igneous rocks Intrusive magma cooling and crystalizing under the earths surface Granite, Basalt, gabbro, peridotite, diorite Granite Extrusive magma cooling and crystalizing on the earths surface Obsidian, Pumice, rhyolite, andesite, basalt Rhyolite Diorite Obsidian Pumice
Metamorphic Form when existing rocks are changed by heat and pressure
Classifying metamorphic rocks Gneiss Foliated Show layers and bands of minerals Slate, schist, gneiss Non- foliated Show blocky crystal shapes Quartzite, Marble Schist Slate
Sedimentary Form when existing rocks break down into sediments Limestone Chalk COAL Shale Sandstone
Rock Cycle
Weathering
Weathering Weathering is the process in which materials on or near Earth s Surface break down and change Two types of Weathering Mechanical Weathering Chemical Weathering
Mechanical Weathering Also called Physical Weathering Process where rocks and minerals break into smaller pieces Does not change the rock composition, only changes size or shape Factors influencing mechanical weathering Temperature Pressure
Factors influencing mechanical weathering Temperature effects weathering Frost Wedging - Freezing temps cause ice to form in cracks in the rock, the ice expands and splits the rock
Factors influencing mechanical weathering Pressure effects weathering Roots of trees put pressure on rocks by wedging themselves into cracks Exfoliation rocks outer layers stripped away over time (like how an onion can be peeled)
Chemical Weathering Process where rocks and minerals undergo changes in their composition. Examples: Water, carbon dioxide, Oxygen and Acid rain all play a part
Chemical Weathering Acid Rain caused by human activity acid causes damage to all Factors that influence chemical weathering Type of rock determines how weathered it can be Temperature also influences how quickly weathering occurs higher the temp, higher the rate of weathering
Influence on Rate of weathering Climate precipitation, temperature and evaporation all influence the rate of weathering Chemical weathering is rapid in higher temperatures, abundant rainfall and lush vegetation Physical weathering is rapid in cool climates where there is repeated freezing and thawing Rock type and composition some rocks decay quicker than others Surface area the more surface area exposed, the quicker the weathering Topography the slope of the landscape promotes erosion and exposes less weathered material
Erosion and Deposition
Erosion and Deposition Erosion removal of rock and soil from its original location Erosion can be performed by water, wind, glaciers, ocean currents and waves. Gravity also contributes to the pulling of materials down a slope Deposition After materials are transported, they are dropped off in a particular location as deposits
Kinds of Erosion Water erosion Water is the most powerful agent of erosion. Rivers and Streams carry sediments to the ocean and carve out large areas of land Waves changing tides and human development have detrimental effects on the shoreline
Other kinds of Erosion Glacial Erosion Glaciers scrape and gouge large parts of the earth because they move as large chunks
Other kinds of Erosion Wind Erosion Wind picks up fine materials and they beat against the earth Prevention: Farmers plant heavy row of trees to prevent crops from blowing over Wind produces sand dunes
Other kinds of Erosion Erosion by living things - Animals burrow into the ground, Humans excavate the land to build
Videos http://www.youtube.com/watch?v=r48zyr-s7v0 http://www.youtube.com/watch?v=a6jcjqrpd_8
Soil
Soil Soil consists of: Regolith: minerals and weathered rock fragments Humus: weathered rock particles and decaying organic matter Water Living organisms Soil forms from mechanical and chemical processes
Soil Profile Soil profile is a vertical sequence of soil layers. Soil varies in composition, texture, structure and color at different depths.
Soil Horizons Soil Horizons Layer of soil O/A Topsoil - organic material, loose leaves, filled with insects, microorganisms B Subsoil Contains fine clay and lower limit of plant roots C bedrock or parent material -contains little organic matter http://www.youtube.com/watc h?v=vqtdfaclwf0
Factors of Soil Formation Climate Most significant factor Temp, wind and amount of rain determines composition of the soil. Topography Slope of ground and orientation towards sun Parent Material The material that has been transported by erosion will have different characteristics than the original soil Biological Organisms Microorganisms, fungi, bacteria contribute different organic materials to the soil Time Newer soils are found along rivers where erosion has taken place and minerals are present. Older soils have had most minerals changed or washed away
Soil Types Pedalfer These soils are rich in Aluminum and Iron. They form in forested, moist-temperate climatic zones, humid climates, such as the southeastern U.S. Large amounts of clay, red-brown color
Soil Types Pedocal These soils are rich in Calcium. They form in dry, arid climates, such as the southwestern U.S. Ground is covered in grasses and brush vegetation. Less clay is present, light gray-brown color
Soil Types Laterites - These soils have been depleted of nearly all elements except iron and aluminum oxides. Form in hot tropical areas, where large quantity of rainfall filters out minerals, giving it an orange or red color. The high rainfall has caused leaching of most of the elements and nutrients from the soil. This is the soil typical of a tropical rainforest. When dried, it becomes very hard and practically waterproof. Ancient structures were built from laterite
Mass Movements
Mass Movements Landforms can change through processes involving wind, ice, water and gravity. Mass movements: the down slope movement of soil and weathered rock resulting from the force of gravity All mass movements occur on a slope Movements range from barely detectable to sudden movements
Triggers for mass movement 1. Material s weight pulls material down the slope 2. Material s resistance to sliding or flowing 3. Water heavy rain and ground saturation acting as lubrication between the grains of soil 4. Steepness of slope 5. Removal of vegetation 6. Earthquakes
Types of mass movements Creep slow, steady, downhill movement of loose weathered earth Moves a few centimeters a year Occurs in permafrost regions You can tell a creep has happed because of the position of previously horizontal structures are tilted.
Types of mass movements Flows Earth materials flow as if they were a thick liquids. Mudflows swift moving mixtures of mud and water Common in Los Angeles basin Lahar volcanic mudflow
Types of mass movements Landslides rapid, downslope movement of earth s materials that occurs when a relatively thin block of soil, rock, and debris separates from the bedrock. Common on steep slopes saturated by water Rockslide same as landslide but with rocks
Types of mass movements Avalanche movement of snow down a slope
Videos of Landslides http://www.youtube.com/watch?v=k1qy8npqccw http://www.youtube.com/watch?v=mknstamia0q http://www.youtube.com/watch?v=94d7iyuoyha http://www.youtube.com/watch?v=leax0uezd-g&feature=related http://www.youtube.com/watch?v=zl7_omqozbo&feature=fvw http://www.youtube.com/watch?v=weuv_gkrhie&feature=relat ed http://www.youtube.com/watch?v=aiczronfgbc&feature=related