Exogenic Processes PDF

EXOGENIC PROCESSES OBJECTIVES Define weathering; Identify and distinguish the two types of weathering; Identify the factors affecting the rate of weathering;  EXOGENIC PROCESS Exogenic = outside Process = series of change Series of changes that happened outside...

EXOGENIC PROCESSES OBJECTIVES Define weathering; Identify and distinguish the two types of weathering; Identify the factors affecting the rate of weathering;  EXOGENIC PROCESS Exogenic = outside Process = series of change Series of changes that happened outside or in the Earth’s surface. include geological phenomena and processes that originate externally to the Earth's surface. They are genetically related to the atmosphere, hydrosphere and biosphere, and therefore to processes of weathering, erosion, transportation, deposition, denudation etc. EXOGENIC PROCESSES WEATHERING EROSION MASS WASTING SEDIMENTATION WEATHERING Process that breaks down or alteration rocks into smaller pieces Types of Weathering Physical Weathering Chemical Weathering Physical Weathering Occurs when rock is physically broken into smaller pieces Effect of changing temperatures Types of Physical Weathering Abrasion – sand and rock carried by wind, water, ice wears away surface rock when rocks collide. Types of Physical Weathering Freeze-thaw or Ice Wedging – water seeps in rock, expands, crack rocks into smaller pieces Types of Physical Weathering Exfoliation – pressure in a rock is released along parallel alignments near the surface of the bedrock as a consequence of the reduction in pressure during uplift and erosion Factors Affecting Physical Weathering Chemical Weathering The process of breaking down rock through chemical changes Caused by rainwater reacting with mineral grains in rocks to form new minerals (clays) and soluble salts Types of Chemical Weathering Acidification – polluting gases, like sulfur dioxide and nitrogen oxide dissolve rainwater to make stronger acids. Types of Chemical Weathering Dissolution – common with limestone. Acidic waters dissolve limestone allowing for additional water to gain entrance Types of Chemical Weathering Hydrolysis – break down of rock by acidic water to produce clay and soluble salts Hydration – water reacts chemically with rocks, modifying its chemical structure E.g. H2O + CaSO4 --> CaSO4 + 2H2O Oxidation – breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-colored weathered surface Factors Affecting Chemical Weathering Dissolution H2O + CO2 + CaCO3 --> Ca+2 + 2HCO3- water + carbon dioxide + calcite dissolve into calcium ion and bicarbonate ion Oxidation 4Fe+2 +3O2 --> 2Fe2O3 ferrous iron + oxygen combine to form ferric iron oxide (hematite) Hydrolysis 2KAlSi3O8 + 3H20 --> Al2Si2O5(OH)4 + 4SiO2 + 2K(OH) Silicate minerals weather to form clay minerals. Biological Weathering Rocks are weakened by different biological agents Classifications: 1. Biological Weathering by Physical Means 2. Biological Weathering by Chemical Compounds Biological Weathering by Physical Means Animals – burrow and push apart rock - create holes on the ground by excavation and move the rock fragment to the surface which become more exposed to other environmental factors that can enhance their weathering Biological Weathering by Chemical Compounds Some Plants and Animals also produced acidic substances that react with the rock and cause its slow disintegration Factors Affecting the Type and Rate at Which Weathering Takes Place a. Climate – areas that are cold and dry tend to have slow rates of chemical weathering and weathering is mostly physical; chemical weathering is most active in areas with high temperature and rainfall Factors Affecting the Type and Rate at Which Weathering Takes Place b. Rock type – the minerals that constitute rocks have different susceptibilities to weathering. Those that are most stable to surface conditions will be the most resistant to weathering. Thus, olivine for example which crystallizes at high temperature conditions will weather first than quartz which crystallizes at lower temperature conditions. Factors Affecting the Type and Rate at Which Weathering Takes Place c. Rock structure - rate of weathering is affected by the presence of joints, folds, faults, bedding planes through which agents of weathering enter a rock mass. Highly- jointed/fractured rocks disintegrate faster than a solid mass of rock of the same dimension Factors Affecting the Type and Rate at Which Weathering Takes Place d. Topography - weathering occurs more quickly on a steep slope than on a gentle one e. Time - length of exposure to agents of weather determines the degree of weathering of a rock QUICK ACTIVITY (10pts) During your recent visit to the cemetery, you noticed the inscriptions on some headstones have become barely legible whereas inscriptions on others are sharp and clear. Cite three possible factors that contributed to the present state of the headstone inscriptions. Support. EROSION The rock particles get carried away by wind, water, ice, and gravity Moves weathered rocks Agents of Erosion Water Wind Ice gravity Erosion by Water Changes the shape of coastline Waves constantly crash against shores. They pound rocks into pebbles and reduce pebbles to sand. Water sometimes takes sand away from beaches. This moves the coastline farther inland Factors Affecting the Type and Rate at Which Weathering Takes Place a. Running Water – encompasses overland flow and stream flow Factors Affecting Stream Erosion Velocity – the ability of stream to erode and transport 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 Erosional and Depositional Landform Created by Streams Alluvial Fan Oxbow Lake Erosion by Water b. Ocean or Sea Waves Barrier Island Spit Erosion by Water c. Groundwater Sinkhole - circular depressions which form through dissolution of underlying soluble rocks or the collapse of a cave’s roof. Tower karst – tall, steep-sided hills created in highly eroded karst regions.  Erosion by Water c. Groundwater Cave/Cavern – forms when circulating groundwater at or below the water table dissolves carbonate rock along interconnected fractures and bedding planes. A common feature found in caverns is dripstone, which is deposited by the dripping of water containing calcium carbonate. Dripstone features are collectively called speleothems, and include stalactites, stalagmites, and columns Erosion by Wind Carries dust, sand, and volcanic ash from one place to another Wind can sometimes blow sand into towering dunes Erosion by Ice Can erode the land In frigid areas and on some mountaintops, glaciers move slowly downhill and across the land. As they move, they pick up everything in their path, from tiny grains of sand to huge boulders Erosion by Ice Glaciers - a moving body of ice on land that moves downslope or outward from an area of accumulation (Monroe et. al., 2007) Types of glaciers: i. Valley (alpine) glaciers — bounded by valleys and tend to be long and narrow Erosion by Ice Glaciers - a moving body of ice on land that moves downslope or outward from an area of accumulation (Monroe et. al., 2007) Types of glaciers: ii. Ice sheets (continental glaciers) — cover large areas of the land surface; unconfined by topography. Modern ice sheets cover Antarctica and Greenland Erosion by Ice Glaciers - a moving body of ice on land that moves downslope or outward from an area of accumulation (Monroe et. al., 2007) Types of glaciers: iii. Ice shelves — sheets of ice floating on water and attached to the land. They usually occupy coastal embayments. Erosion by Gravity Gravity pulls any loose bits down the side of a hill or mountain Gravity Erosion is better known as Mass Movement Weathering vs. Erosion Weathering causes the rocks to break down Erosion and transport moves the sediments downhill to another place MASS WASTING The movement of rock, soil and regolith downward due to the action of gravity Downslope movement of masses of bedrock debris, regolith or soil, under the direct influence of gravity Factors that triggered Mass Wasting Over-steepened Slope – Rapid movements are commonly found in steep slopes while slow movements are found on gentle slopes Water – rainwater adds weight and acts lubricants to weathered material Earthquake – the vibration moves weathered rocks Vegetation Removal – the lack of vegetation cover to hold the loose particles. Classifications a. Slump e. Debris Slide b. Solifluction f. Debris Flow c. Earthflow g. Rock Fall d. Mudflow h. Soil Creep SEDIMENTATION A natural process in which a material is carried to the bottom of bodies of water and forms solid.