Exogenic Processes PDF

EXOGENIC PROCESSES  EXOGENIC PROCESSES UNIFORMITARIANISM “the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes.” What are these processes? Er...

EXOGENIC PROCESSES  EXOGENIC PROCESSES UNIFORMITARIANISM “the theory that changes in the earth's crust during geological history have resulted from the action of continuous and uniform processes.” What are these processes? Erosion Weathering Deposition  EXOGENIC PROCESSES EROSION - breaking of rocks into smaller pieces and removal of those rocks and pieces by wind, water, ice or gravity. WEATHERING - chemical and physical processes that break down rock and other substances, heat, cold, water, ice and gases contribute DEPOSITION - process in which sediment is laid down in new locations  EXOGENIC PROCESSES TWO TYPES OF WEATHERING 1.) Mechanical-rock is physically broken down into smaller pieces -- usually works slowly -- over long periods of time, can wear down mountains  EXOGENIC PROCESSES Action of Animals - burrowing by moles. Gophers, prairie dogs and insects loosens soil and breaks apart rocks.  EXOGENIC PROCESSES Freeze Thaw - important in cold climates, H2O seeps into cracks in rocks, freezes and expands which forces the rock apart this is called FROST WEDGING.  EXOGENIC PROCESSES Release of Pressure - erosions removes material from surface of a mass of rock, pressure on rock is reduced which causes the outside of the rock to crack and flake off.  EXOGENIC PROCESSES Plant growth - roots enter cracks of rocks, as plant grows, so will roots causing cracks to get larger.  EXOGENIC PROCESSES Abrasion - the grinding away of rock by other rock particles carried in water, ice or wind.  EXOGENIC PROCESSES 2.) Chemical - process that breaks down rock through chemical processes. -- process works with mechanical weather. -- creates holes or soft spots in rocks. -- rock breaks into pieces creating larger surface area for chemical weathering to work.  EXOGENIC PROCESSES White lichens cover a blue granite gravestone like The effects of acid rain can be seen on this close snow near Lake Champlain, New York. Lichens, up of this statues face. The acid rain has reacted symbiotic organisms that combine fungi and algae, with the mineral grain of the rock which has can be powerful weathering agents, secreting over time caused cavities to form as well chemicals called chelates that work to break down wearing away the definition of the facial rock. features.  EXOGENIC PROCESSES Water - dissolves rock and carries other substances that break down rock, ie O, CO2 and other substances Oxygen – combines with Iron to form rust, this is called oxidation -- rust makes rocks soft and crumbly and causes red/brown color Carbon dioxide – when dissolved in water forms carbonic acid which easily weathers some rocks like marble and limestone  EXOGENIC PROCESSES Living organisms – plant roots produce weak acid that breaks down rock, ie. lichens Acid rain – burning of fossil fuels puts S, C and N in the air. These compounds react with water vapor, rain produced is more acidic than normal = acid rain. -- Acid rain rapidly causes chemical weathering  EXOGENIC PROCESSES Rate of Weathering 1.) Type of rock - Minerals determine how fast the rock weathers - Minerals that are soft, dissolve easily = fast weathering 2.) Surface Area - Spaces increase surface area of rock allowing weathering to occur more quickly - More surface area = more weathering  EXOGENIC PROCESSES 3.) Climate More moisture = increase physical and chemical weathering Warm/moist climate = increase chemical weathering chemical reactions occur more quickly at high temperatures Cold/moist climate = increase physical weathering Human activities also can increase the rate of chemical weathering more people in an area = more pollution = more acid rain (chemical weathering)  EXOGENIC PROCESSES Erosion the process by which weathered sediments are carried/transported Agents of Erosion: Agents of erosion are the materials or forces that move sediments from one place to another. Gravity (Mass Movements) Wind Running Water (Streams) Waves  EXOGENIC PROCESSES GRAVITY – pulls weathered sediments down steep slopes (called mass wasting) mass movements occur when the force of gravity is greater than the force of friction (keeps weathered sediments from moving) Types of Mass Wasting Fast – landslides, mudslides Slow – soil creep, slump  EXOGENIC PROCESSES SLUMPING Cliffs formed from boulder clay, material deposited by glacial periods, are susceptible to high rates of coastal erosion. The soft boulder clay is quickly eroded through hydraulic action and abrasion.  EXOGENIC PROCESSES LANDSLIDES In areas of more resistant cliff material erosion is greatest when waves break at the foot of a cliff. This causes erosion at the base of the cliff. This creates a wave-cut notch in the base of the cliff. As the notch increases in size, the weight of the cliffs above becomes too much to support, leading to a landslide.  EXOGENIC PROCESSES ROCKFALL A rockfall involves rock fragments breaking away from the cliff face, often due to freeze-thaw weathering.  EXOGENIC PROCESSES MUDSLIDE Mudslides occur when saturated soil and weak rock flow down a slope. These typically occur where cliffs are made up of boulder clay.  EXOGENIC PROCESSES Wind – heavy winds can move sand, but rarely more than a meter above the ground and only where it is very dry light winds can only move the smallest sediments occurs in arid climates and coastlines where loose sediments are available  EXOGENIC PROCESSES DEFLATION ABRASION process where winds winds blow sand blow away loose against rocks and other sediments, lowering the objects causing them to be land surface. "sandblasted“.  EXOGENIC PROCESSES Running Water – running water is the dominant form of erosion the amount (volume) of water in a stream is called the stream's discharge  EXOGENIC PROCESSES Meander - bends in a streams channel stream moves fastest along the outside of a curve; slowest along the inside erosion occurs where the stream is moving fastest - causes the shape of the Channel Fastest stream flow occurs at a point farthest away from the bottom and the sides where drag occurs. This means that the rate of flow is greatest in the center near the surface. Flow is fast if the channel is narrow. The rate slows if the channel widens or if the stream enters a lake or the ocean.  EXOGENIC PROCESSES Meander - bends in a streams channel stream moves fastest along the outside of a curve; slowest along the inside Erosion occurs where the stream is moving fastest.  EXOGENIC PROCESSES Meandering streams change shape is because small disturbances in the river bed. EXOGENIC PROCESSES  forms when a wide A delta is a landform at the meander from a river is cut off, mouth of a river, where the creating a free-standing lake. This usually happens due to river deposits sediment as it erosion and deposition of flows into another body of sediments during river flow water, such as an ocean, sea, changes. or lake.  EXOGENIC PROCESSES Waves size of waves depends on how long wind blows in one direction water particles rise and fall in circular paths over deep ocean water when wave reaches shallow water near shore, friction causes the bottom of the wave to move more slowly (“breaks”)