Exogenic Processes: Erosion and Deposition PDF

EXOGENIC PROCESS (EROSION AND DEPOSITION) JENNIFER C. BELO SHS Teacher A.Erosion H. Drumlin B. Deposition I. Dune C. Abrasion J. Deflation D. Alluvial fans K. Ventifacts E. Oxbow lake...

EXOGENIC PROCESS (EROSION AND DEPOSITION) JENNIFER C. BELO SHS Teacher A.Erosion H. Drumlin B. Deposition I. Dune C. Abrasion J. Deflation D. Alluvial fans K. Ventifacts E. Oxbow lake L. Barrier island F. Glacier M.Spit G. Arete  DEPOSITION- is the geological process on whuch sediments, soil and rocks are added to a land form or land mass. Wind, ice, water, and gravity transport previously weathered surface material, which at the loss of enough kinetic energy in the fluid, is deposited, building up layers of sediment.  ABRASION- the process of scraping or wearing away. - an area damaged by scrapping or wearing away.  ALLUVIAL FAN- is a fan- or cone- shaped deposits of sediment crossed and built up by streams. If a fan is built up by the debris flows it is properly called a debris cone or colluvialfan.  OX BOW LAKE- is a U- SHAPED LAKE that forms when a wide meander from the main stem of a river is cut off, creating a free- standing body of water. This landform is so named for its distinctive curved shaped, with resembles the bow pi of an oxbow.  GLACIER- is a persistent body of dense ice that is constantly moving under its own weight; it forms where the accumulation of snow exceeds its ablation over many years, often centuries.  ARETE- is a narrow ridge of rocks which separates two valleys. It is typically formed when two glacier erode parallel U-shaped valleys.  DRUMLIN- are also gated teardrop-shaped hills of rock, sand, and gravel that formed under moving glacier ice. They can be up to 2 kilometers (1.25 miles) long.  DUNE- a hill or ridge of wind- blown sand. Dunes are capable of moving by the motion of their individual grains but usually keep the same shaped.  DEFLATION- in geology, erosion by wind of loose material from flat areas of dry, un cemented sediments such as those occurring in deserts, dry lake beds, floodplains, and glacial outwash plains.  VENTIFACTS - a stone shaped by erosive action of wind blown sand. - a ventifact is a rock that has been abraded, pitted, grooved, or polished by wind-driven sand or ice crystals.  BARRIER ISLAND- are coastal landform sand a type of dune system that are exceptionally flat or lumpy areas of sand that form by wave and tidal parallel to the mainland coast. They usually occuring chains, consisting of anything from a few islands to more than a dozen  SPIT- or sandspit is a deposition bar or beach landform off coasts or lake shores. It develops places where re-entrance occurs, such as at a cove’s headlands by the process of long shore drift by longshore currents. A. WEATHERING - The disintegration and decomposition of rock at or near the Earth surface.  B. EROSION - the incorporation and transportation of material by a mobile agent such as water, wind, or ice. VARIOUS AGENTS OF EROSION  1. RUNNING WATER A. Running water compass both overland flow and stream flow.  B. FACTORS THAT AFFECT STREAM EROSI0N AND DEPOSITION VELOCITY -dictates the ability of stream to erode and transport; controlled by gradient, channel size and shape, channel roughness, and the amount of water flowing in the channel.  DISCHARGE -volume of water passing through a cross-section of a stream during a given time; as the discharge increases, the width of the channel, the depth of flow, or flow velocity increase individually or simultaneously. VARIOUS PROPERTIES OF STREAM CHANNEL CHANGE FROM ITS HEADWATERS TO ITS MOUTH from head waters to mouth: channel slope channel roughness , discharge , channel size , flow velocity  STYLES OF EROSION VERTICAL EROSION makes a river channel deeper. This happens more in the upper stages of a river. (The V-shaped help you remember he V-UPPER STAGES). Lateral erosion makes a river wider, this occurs mostly in the middle and lower stages of a river.  LATERAL EROSION Refers to the widening of a stream channel or valley. When a stream is high above its base level, downcutting will take place faster than lateral erosion; but as the level of the stream approaches its base level, the rate of lateral erosion increases.  HEADWARD EROSION  Is erosion at the origin of a stream channel, which causes the origin to move back away from the direction of the stream flow, and so causes the stream channel to lengthen.  Streamflow erosion occurs by: Hygraulic action, abrasiin, solution Streams transport their sediment load in three ways: in solution (dissolved load), in suspension (suspended load), sliding and rolling along the bottom (bed load) A stream’s ability to transport solid particles in described by: Competence (size of the largest particle that can be transported by the stream) and capacity (maximum load a stream can transport under given conditions.)  Erosional landsform: River valleys, water falls, potholes, terraces, gulley/rills, meanders (exhibit both erosional and depositional features), oxbow lake, peneplane. Deposiotional landform: alluvial fans/cones, natural levees, deltas.  2. OCEAN OR SEA WAVES A.Wave – a lond body of water curling into an arched form and breaking on the shore. Crest and tough, wave length (L), wave heigth (H), steepnes (H/L), period (P), velocity (C=L/T) waves are classified by the generation force: wind-generated waves, tsunami, tides, seiches (we’ll focus on wind-generated winds)  Wind speed, wind duration, fetch (the distance the wind has travelled across water) Orbital motion of water in waves. In deep water, there is little or no orbital motion at depths greater than half the wavelength. As wave moves into shallower water, it starts to ‘feel the bottom’ at a depth equal to the wave base (D=L/2). C (velocity) , L , H , T does not change as wave moves into shallow water.  C. Waves erode and move sediment along the shore Shoreline erosion processe: hydraulic action, abrasion, corrosion transport by waves and created by waves erosion and current: long shore current, beach drift  D. FEATURES CREATED BY WAVE EROSION AND DEPOSITION erosional features: wave-cut cliff, wave- cut platform, marine terrace, headland, stacks and sea arches depositional features: beach, spit, baymouth bar, tombolo, barrier island 3. GLACIERS -moving body of ice on land that moves downslope or outward from an area of accumulation.  TYPES OF GLACIERS 1. Valley (alpine)- glaciers are bounded by valleys and tend to be long and narrow.  2. Ice sheets (continental glaciers)- cover large areas of the land surface and unconfined by topography. Modern ice sheets cover Antarctica and Greeanland.  3. Ice shelves- are sheets of ice floating on water and attached to the land. They usually occupy coastal embayments.  HOW GLACIERS ARE FORMED: Glaciers are formed in regions where more snow falls than melts. Snow accumulates then goes through compaction and recrystallization to form firm and eventually into glacial ice.  PROCESSES RESPONSIBLE FOR GLACIAL EROSIN: Plucking- lifting pieces of bedrock beneath the glacier. It is responsible for creating roche moutonnee. Abrasion- grinding and scraping by sediments already in the ice.  LANDFORMS CREATED BY VALLEY GLACIER EROSION: Cirque Valley Tarn U-shaped valley Arète Paters Horn nosterlakes Hanging fjord  LANDFORMS CREATED BY CONTINENTAL GLACIERS Roche moutonnee  TWO TYPES OF GLACIAL DRIFT 1.Till- deposited directly by ice, unsorted, and composed of many different particle sizes. 2.Stratified Drift- deposited by the glacial melt water and thus, has experienced the sorting action of water.  4. WIND -A natural movement of air of any velocity  WIND ERODES: 1. Deflation- removal of loose, fine particles from the surface. -results to features such as blowout and desert and desert pavement. 2. Abrasion- grinding action and sandblasting. -yields ventifacts and yardangs.  TWO TYPES OF WIND DEPOSITS 1.Dunes- hills or ridges of wind- blown sand. 2. Loess- extensive blankets of silt that were once carried in suspension. SIX MAJOR KINDS OF DUNES 1.Barchan dunes 2.Transverse dunes 3.Barchanoid dunes 4.Longitudinal dunes 5.Parabolic dunes 6.Star dunes  PRIMARY SOURCES OF SEDIMENTS CONTRIBUTING TO LOESS Deserts Glacial deposits  5. GROUNDWATER -water within the earth especially that supplies wells and springs.  KARST TOPOGRAPHY AND ITS ASSICIATED LANDFORMS Karst topography- a distinctive type of landscape which develops as a consequence of subsurface solution. It consists an assemblage of landforms that is most common in carbonate rocks but also associated with soluble evaporate deposits.  CAVE/CAVERN-forms when circulating groundwater at or below the water table dissolves carbonate rock along interconnected fractures and bedding planes. SINKHOLES (DOLINES)-circular depressions which form through dissolution of under lying soluble rocks or collapse of a cave’s roof SOLUTION VALLEYS-closed depressions which form from coalescing sinkholes DISAPPEARING STREAMS-surface streams that flows and “disappears” into solution cavities and at other places may re-emerge as a spring. TOWER KARST- tall, steep-sided hills created in highly eroded karst regions.  6. GRAVITY MASS WASTING is the downslope movement of soil, rock, and regolith under the direct influence of gravity. FACTORS THAT CONTROL MASS WASTING PROCESSES include: SLOPE ANGLE- As slope angle increases, the tendency to slide down the slope becomes greater. Role of water: adds weight to the slope, has the ability to change angle of repose, water pore pressure reduces shear strength of materials, reduces friction on a sliding surface. Presence of clays that expand when wet and shrink when dry Weak materials and structures that become slippage surfaces if weight is added or support is removed.