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Weathering, erosion, and mass wasting
 

Weathering, erosion, and mass wasting

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    Weathering, erosion, and mass wasting Weathering, erosion, and mass wasting Presentation Transcript

    • WEATHERING, EROSION, AND MASS WASTING
    • WEATHERING
      • Two types of weathering are mechanical and chemical .
      • Mechanical weathering is the physical break up of rock exposing more surface area by:
      • Frost wedging – common in mountains and middle latitudes
      • Unloading
      • Biological activity
      • Frost Wedging
      • When water freezes it expands by about 9% and exerts tremendous force. This force breaks off rocks, tumble and pile up at the bottom of the cliff into large pies called talus.
      • Unloading
      • Exposed rock reduces pressure causing the outer layers to expand. The outer layers separate from the rest of the rock by a process called exfoliation .
      • Biological activity
      • Plant roots grow into rocks breaking rocks apart.
      • Chemical weathering is the transformation of rock into one or more new compounds.
      • Water is the most important agent of chemical weathering
      • The oxygen dissolved in water reacts with certain minerals forming oxides , such as iron oxides in soil (yellowish or red soils)
      • Water falling through the atmosphere absorbs carbon dioxide forming weak carbonic acid . This acid reacts with many minerals, for example limestone.
      • Water in the atmosphere reacts with sulfur oxides and nitrogen oxides from the burning of coal and petroleum to form acid rain . The acid rain reacts with many minerals.
      • Chemical weathering of granite forms the minerals feldspar and quartz . The feldspar reacts with the carbonic acid forming clay . The quartz is resistant to weathering and remains unchanged.
      • The rate of weathering is influenced by mechanical weathering , rock characteristics, and climate . For example
      • Granite weathers slower than marble or limestone.
      •  
      • Climate favorable to weathering have high temperatures and abundant moisture .
      • Where is chemical weathering the slowest?
    • EROSION
      • Soil erosion is a natural part of matter recycling.
      •  
      • The rate of soil erosion depends on soil characteristics, climate , slope , and type of vegetation .
    •  
      • Types of Water Erosion
      • Sheet erosion – thin sheets of water carriers away soil particles
      • Rills – tiny streams of water
      • Gully erosion – deep trenches
      • Wind erodes soil much more slowly. However prolonged drought can remove large quantities of exposed soil.
      • Human activities that increase the rate of soil erosion are land clearing due to development and road building. Sedimentation is the number one stream pollutant in North Carolina.
    • MASS MOVEMENT (WASTING)
      • MASS MOVEMENT (WASTING) – the down slope movement of rock and soil due to gravity
      • Triggers of mass movements
      • Water-logged soils
      • Over-steepened slopes from road building and development
      • Removal of vegetation
      • Earthquakes
      • Types of Mass Movements
      • Rock falls – rock or rock fragments fall off
      • Landslides – a block of material suddenly moves down along a flat inclined surface
      • Slump – a block of materials move down along a curved surface
      • Mudflows - contain a high amount of water, occur quickly, occur in mountainous areas
      • Earth flows move relatively slowly, form a tongue-shaped mass
      • Creep – the slowest type of mass movement, travels few millimeters to centimeters per year, freeze-thaw cycles contributes to creep.