Exogenic Processes PDF

Exogenic Processes           Exogenic processes are external processes that occur at or near the surface of the Earth. It is part of rock cycle. It is responsible for transforming rock into sediment. Exogenic processes are very destructive, this are responsible for include degradation and sculpting...

Exogenic Processes           Exogenic processes are external processes that occur at or near the surface of the Earth. It is part of rock cycle. It is responsible for transforming rock into sediment. Exogenic processes are very destructive, this are responsible for include degradation and sculpting of Earth’s Surface. Three types of exogenic process are the following: weathering, mass wasting, and erosion.  WEATHERING 1. Weathering – the physical breakdown and/or chemical alteration of rocks at or near Earth’s surface because of different agents like gravity, water, wind and waves. It is a degradation process that does not involve movement of materials. There are three types of weathering: physical or mechanical, chemical, and biological weathering. `    Three Types of Weathering 1. Physical Weathering is the breaking up of large rocks into smaller fragments without changing the rock’s mineral composition. It takes place in different ways depending on the factor that acts on the rock such as pressure, warm temperature, water, and ice.  Types of Physical Weathering 1. Frost Wedging occurs in regions where temperature fluctuates above or below freezing point, resulting in freeze-thaw cycle. Water that enter through the cracks and empty spaces of rocks expand when it freezes due to enormous outward force exerted by ice. When the ice thaws, water can flow further into the crack. Repeated freeze-thaw cycles weaken the rock and break up rocks into smaller fragments.  2. Insolation Weathering or Thermal Stress results from the expansion and contraction of rocks caused by temperature changes. You learned from your basic science that heat causes expansion of materials. This repeated heating and cooling of rock over daily cycles, progressively breaking apart the grains of rock.  3. Unloading or Pressure Release occurs when the overlying rock is eroded away, causing the outer rock layer to expand more than the layers underneath. This expansion may separate the outer rock from the body. This process is evident in intrusive igneous rocks. The overlying material exerts tremendous pressure on the igneous rock. and when erosion removes the overlying materials, the presence on the igneous rocj is released, causing the outer portion to expand causes sheets of rocks to break away often referred to as sheeting.  2. Chemical Weathering is the weakening or disintegration of rocks and the formation of new compounds or new substances caused by chemical reactions.  Types of Chemical Weathering 1. Oxidation is the process in which oxygen reacts with the rock and changes its mineral composition. The oxygen in the humid air or oxygen dissolved in water will oxidize the rocks. Reddish-brown rust will appear on the surface of iron-rich minerals which easily crumbles and weakens the rocks.  2. Hydrolysis is the chemical breakdown of a substance when combined with water. Many common minerals are susceptible to hydrolysis, particularly the silicate minerals (oxygen and silica).  3. Carbonation and Solution is a common type of solution that involves carbon dioxide and water molecules reacting with, thereby decomposing rock material. It is most effective in carbonate rocks (CO3).  3. Biological Weathering or Biological Action can be either chemical or mechanical weathering as this weathering caused by organisms -- animals, plants, fungi and microorganisms such as bacteria.    MASS WASTING 2. Mass Wasting is a collective term for the downslope transport of surface materials like rocks, soil, and regolith in direct response to gravity. The force of gravity encourages rock, sediment, and soil to move downhill on sloping surfaces.      Types of Mass Wasting There are different types of mass wasting processes. Each process is defined by the type of materials involved and the velocity and nature of movements. 1. Rock and Debris Fall.           Rock fall occur when a piece of rock or mass of rocks become dislodged and makes free-fall along a steep cliff. Debris fall is similar to rock fall, except that it involves a mixture of soil regolith, vegetation, and rocks. At the base of the cliff is an accumulation of fallen materials called talus.  2. Landslides  Landslides are another type of mass wasting. They are sudden fast movement of cohesive mass of soil, rock, or regolith. They occur in two types: translational and rotational slides. Translational slides involve the movement of mass of materials along a well-defined surface, such as bedding plane, foliation surface, or joint surface. Rotational slides occur when the descending materials move en masse along a concave, upward curved surface.       3. Flows           A type of mass wasting that occurs when soil, rock, or other material behaves like a liquid or fluid. Flows may be slurry flows or granular flows. Slurry flows consist of a mixture of rocks/ or regolith with 20% to 40% water. Granular flows contain 0 to 20% water.    EROSION 3. Erosion It is part of the constant recycling of Earth materials. A natural process; It is the transporting of weathered sediments by agents of erosion to different places. Agents of Erosion 1. Water – running water is the primary agent of erosion on Earth. Most running water is found in streams and rivers.  Types of Erosion by Water 1. Splash Erosion – raindrops cause tiny particles of soil to be detached and move out. The impact of a falling raindrop creates a small crater in the soil, ejecting soil particles.  2. Sheet Erosion – Raindrops break apart the soil structure which moves down the slope as water flows overland as sheet.  3. Rill Erosion - Refers to the development of small, ephemeral concentrated flow paths which function as both sediment source and sediment delivery system for erosion in hillslopes.  4. Gully Erosion - After heavy rain, water flows in narrow channels, eroding gullies into great depth.  5. Valley Erosion - Continuous water flow alongside land and move downward, which deepens a valley.  6. Bank Erosion - Continuous flow of water wears out stones along bank of streams and rivers.  7. Coastline Erosion - Waves from the ocean and seas crash against the shore, pounding the rocks into pebbles and reducing the pebbles sand. Sand is also removed from the beaches, which changes the coastline.  8. Seaside Cliff Erosion - The battering of ocean waves erodes seaside cliffs, forming hales that create caves. Continuous pounding of waves may create an arch that may fall, leaving nothing but rock columns called sea stocks.    2. Ice/ Glacier - a thick large mass of ice formed hundreds or thousands of years mostly in remote areas like in the poles or in high mountains. It moves very slowly. Glaciers are capable of great erosion. They can erode land through plucking and abrasion.  Plucking -  is the process by which rocks and other sediments are picked up by a glacier. They freeze to the bottom of the glacier and are carried away by the flowing ice. Abrasion is the process in which a glacier scrapes underlying rock. The sediments and rocks frozen in the ice at the bottom and sides of a glacier act like sandpaper. They wear away rock. They may also leave scratches and grooves that show the direction the glacier moved. These grooves are called glacial striations.    3. Wind – carries dust, sand, and volcanic ash from one place to another. It can also erode materials until nothing is left.