LESSON 3_Exogenic Processes.pdf

Earth & Life Science Lesson 3: Exogenic Processes  Learning Competencies The learners shall be able to: Explain how the products of weathering are carried away by erosion and deposited elsewhere. “What do you see?” The Nature of Exogenic...

Earth & Life Science Lesson 3: Exogenic Processes  Learning Competencies The learners shall be able to: Explain how the products of weathering are carried away by erosion and deposited elsewhere. “What do you see?” The Nature of Exogenic Processes Weathering Geological phenomena and processes that originate externally to the Earth's surface. Breakdown of rock material at and near water the Earth’s surface due to disintegration & decomposition caused by low temperature, low pressure & contact with Weathering Mass Wasting Physical Weathering Chemical Exogenic Slow Mass Wasting Processes Downslope movement of rock material that occurs without the assistance of a geomorphic agent due to gravity Fast Mass Wasting Weathering Weathering can happen in the presence of the action of Breakdown of rainwater, variable extreme temperature, and different biological activities. rock material at and near Earth’s surface ❑Physical/Mechanical Weathering is a process wherein rocks are broken down into smaller pieces without changing their chemical composition due to several factors like fluctuating temperatures and pressure, and biological activity. Rocks by the sea change shape due to the force of water during high tide. ❑ Chemical Weathering is a process wherein rock materials are changed into other substances that have different physical and chemical compositions. Physical Weathering  1. UNLOADING happens when, through erosion or uplift, thick layers of sediments overlying deeply buried in rocks are removed. 1. UNLOADING happens when, through erosion or uplift, thick layers of sediments overlying deeply buried in rocks are removed. Exfoliation – Exfoliation dome – unloaded, exfoliating outcrop of rock with a dome-like surface form the successive removal of the outer rock sheets, each broken is an exfoliation sheet. 2. THERMAL EXPANSION & CONTRACTION repeated heating and cooling of materials cause rigid substances to crack  and separate. 3. FREEZE-THAW WEATHERING occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart (ice wedging).  Ice wedging causes potholes to occur in streets 4. SALT CRYSTAL GROWTH The granular disintegration or fragmentation of rock material produced by salt crystal growth. 5. HYDRATION Water molecules attach to the crystalline structure of a mineral without causing a permanent change in that mineral’s composition  Hydrated: expand ; dehydrated: shrink Chemical Weathering Hydrolysis is a process where water reacts with a mineral to form a new mineral.  (i.e., halite) dissolves in a liquid (i.e., water). Dissolution is a process wherein a solid The karst topography is a landscape formed by the dissolution of carbonate rocks Chemical Weathering OXIDATION occurs when there is chemical combination of oxygen with a mineral to form an entirely different mineral in which at least one of the elements has a higher ionic charge. Oxidation gives the red color of some desert landscapes. Factors Affecting Weathering of Rocks ❑Climate mainly includes the amount of moisture in the air and temperature where weathering takes place. ❑The higher the elevation of an area, the more susceptible it is to weathering since it is more exposed to environmental factors. ❑Weathering rapidly occurs when there is a large surface area exposed to surface processes. ❑When a block is broken into smaller pieces, it has a larger total surface area which makes it  more susceptible to weathering. Mass Wasting The downslope transport of surface materials in direct response to gravity It is different from erosion because mass wasting does not need any transporting medium such as wind, water, or glacial ice. The massive landslide at St. Bernard in Southern Leyte last 2006 was triggered by a minor earthquake and continuous rainfall. ❑ The disaster resulted in an estimated death of 1,800 people. ❑A school containing 246 students was also buried underground. Slow Mass Wasting 1. CREEP Common material: soil slow migration of particles to successively lower elevations Usually less than a few cm per year Most widespread and most persistent because it nearly affects all slopes that have weathered rock fragments at the surface Slow Mass Wasting 2. SOLIFLUCTION Common material: soil “soil flow”; slow downslope movement of water-saturated soil and/or regolith Most common in high-latitude tundra  regions that have permafrost; the active layer freezes during winter and thaws during summer Fast Mass Wasting 1. FALLS Common  material: rocks Consists of Earth materials plummeting downward freely through the air Rock falls either: (1) one by one as weathering weakens the bonds between individual clasts & the rest of the cliff, or (2) as large rock masses that fall from a cliff face or an overhanging ledge Fast Mass Wasting 2. AVALANCHES  Common material: ice/snow/debris/rock Much of the involved material is pulverized and flows rapidly as an airborne density current along Earth’s surface Fast Mass Wasting 3. SLIDES Common material: earth/debris/rock A cohesive or semi cohesive unit of Earth material slips downslope in continuous contact with the land surface Fast Mass Wasting 4. FLOWS Common material: mud/debris Masses of water-saturated  unconsolidated sediments that move downslope These involve considerable churning and mixing of the materials as they move. Erosion ❑ Erosion is the  transportation of weathered rocks. ❑Agents like running water or rivers, wind, gravity, groundwater, wave currents, and glaciers contribute to erosion. ❑Erosion has different types: water erosion, wind erosion, and glacial erosion. Types of Erosion ❑Water erosion is a type of erosion where water carries the sediments to different bodies of water such as rivers. ❑The high amount of rainfall contributes to susceptibility of the soil to water erosion. Grand Canyon in Arizona, a product of water erosion ❑ Wind erosion happens when light materials, such as small rocks and pebbles, are carried by the wind to different places.  ❑Glacial erosion happens when a glacier, or a river of highly-compact ice, move downhill due to its weight. ❑It plucks chunks of rocks and causes scraping between the ice and the rock. Rock shaped by wind erosion Causes of Erosion ❑Soil erodibility is the vulnerability of soil to erosion caused by rainfall intensity, soil properties, crop cover, and slope. ❑The texture of the soil is the most significant contributing factor to erodibility although structure, organic matter, and permeability may also affect it.  ❑Overgrazing by livestock or by indigenous animals may remove vegetation leaving the soil more vulnerable to erosion. ❑Cutting of trees and removal of vegetation to provide lumber can also result in large amounts of erosion. ❑Use of pesticides, herbicides, and fuel oils also pollutes the soil. Salt can also contaminate soil due to the high salinity of irrigation water as it passes over croplands. Preventing Soil Erosion Application of organic fertilizer ❑ Shaping steep terrains to ❑ Building retaining walls produce flat areas ❑ Reducing farmland conversion ❑ Planting vegetation ❑ Batad rice terraces