GEOG101 Chapt03 lecture
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GEOG101 Chapt03 lecture






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    GEOG101 Chapt03 lecture GEOG101 Chapt03 lecture Presentation Transcript

    • Overview
      • Earth Materials
      • Geologic Time
      • Movements of the Continents
      • Tectonic Forces
      • Gradational Processes
      • Landform Regions
    • Earth Materials
      • Igneous Rocks
      • Sedimentary Rocks
      • Metamorphic Rocks
    • Igneous Rocks
      • Formed by the cooling and solidification of molten rock
      • Magma: molten rock below ground
        • Cooling forms intrusive igneous rocks
          • Granite
      • Lava: molten rock above ground
        • Cooling forms extrusive igneous rocks
          • Basalt, pumice, obsidian
      • Composition of magma and lava plus cooling rate determines the minerals that form
    • Sedimentary Rocks
      • Composed of eroded particles of gravel, sand, silt, and clay
      • Rocks evolve in horizontal strata
        • Compressed by weight of additional deposits and cemented by water and certain minerals
        • Type of sediment determines rock type
          • Large, rounded particles form conglomerates
          • Sand forms sandstone
          • Silt and clay form shale or siltstone
          • Organic materials form limestone or coal
    • Metamorphic Rocks
      • Formed from igneous or sedimentary rocks by earth forces that produce heat, pressure, or chemical reactions
        • Mineral structure is changed
          • Shale becomes slate
          • Limestone may become marble
          • Granite may become gneiss
    • Geologic Time
      • Earth formed about 4.7 billion years ago
      • Theory of continental drift
        • Based on early 20 th -century work of Alfred Wegener
        • All land masses were once united in a supercontinent; continents drifted apart over many millions of years
          • Pangaea: “all Earth”
        • Forerunner of plate tectonics theory
    • Movements of the Continents
      • Plate tectonics theory
        • Asthenosphere
          • Partially molten layer above the core and lower mantle
        • Lithosphere
          • Outermost layer of the earth (the crust and upper mantle)
          • 12 large and numerous small plates that slide or drift slowly over the asthenosphere
            • May be due to convection of molten material in asthenosphere
    • Movements of the Continents
      • Divergent plate boundaries
        • Plates move away from each other
      • Transform boundaries
        • One plate slides horizontally past another
      • Convergent boundaries
        • Plates move toward each other
          • Subduction may occur
            • One plate is forced beneath another
      • Earthquakes and volcanic activity may occur in the vicinity of plate boundaries
        • Ring of Fire
    • Tectonic Forces
      • Diastrophism
        • Earth force that folds, faults, twists, compresses rock
      • Volcanism
        • Earth force that transports subsurface materials to or toward the surface of the earth
    • Diastrophism
      • Broad warping
        • Bowing of a large region of the earth’s surface
      • Folding
        • Layers of rock are forced to buckle
      • Faulting
        • Rock is broken or fractured
          • Escarpments, rift valleys
        • Earthquake
          • Movement along a fault or point of weakness
        • Tsunami
          • Sea waves generated by an earthquake, volcanic eruption, or underwater landslide
    • Volcanism
      • Usually at or near plate intersections
      • Also at hot spots
      • Strato or composite volcano
        • Explosive, steep sides
      • Shield volcano
        • Non-explosive, gently sloping
      • Magma may not reach the surface
      • Lava may flow through fissures or fractures without forming a volcano
    • Gradational Processes
      • Reduction of the land’s surface
        • Weathering
        • Mass movement
        • Erosion
    • Weathering
      • Processes that fragment and decompose rock
      • Mechanical
        • Physical disintegration
          • Frost action
          • Salt crystals
          • Root action
      • Chemical
        • Decomposition as a result of chemical reactions
          • Oxidation
          • Hydrolysis
          • Carbonation
    • Mass Movement
      • Downslope movement of material due to gravity
        • Avalanches
        • Landslides
        • Soil creep
      • Talus
        • Landform created by the accumulation of rock particles at the base of hills and mountains
    • Erosional Agents and Deposition
      • Wind, water, and glaciers
        • Carve, wear away, and remove rock and soil particles
      • Material is deposited in new places
        • New landforms are created
    • Running Water
      • Most important erosional agent
      • Ability to erode depends upon:
        • Amount of precipitation
        • Length and steepness of the slope
        • Kind of rock and vegetation cover
      • Load of a stream
        • Materials transported by a stream
        • Decline in velocity results in deposition
          • Deltas: where streams meet bays, oceans, and lakes
          • May be deposited in adjacent plains (floodplain)
    • Stream Landscapes
      • Humid areas
        • Waterfalls
        • V-shaped channels
        • Floodplains
        • Meandering streams
        • Oxbow lakes
        • Natural levees
      • Arid areas
        • Lack of vegetation increases erosional forces
        • Playas
        • Alluvial fans
        • Arroyos
        • Washes
        • Buttes and mesas
    • Groundwater
      • Aquifer
        • Porous underground structure bearing water
      • Water table
        • Upper level of the water within an aquifer
        • Ponds, lakes, marshes, and streams form when land surface dips below the water table
    • Groundwater
      • Solution
        • Chemical process by which groundwater (particularly when combined with CO 2 ) dissolves soluble materials
        • Significant effect on limestone
          • Underground caverns, stalactites, stalagmites, sinkholes
      • Karst topography
        • Limestone region marked by sinkholes, caverns, and underground streams
    • Glaciers
      • Huge mass of slowly moving land ice
      • Covered a large part of the earth as recently as 10,000-15,000 years ago
      • Form only where annual snowfall exceeds annual snowmelt and evaporation
        • The weight of the snow causes it to compact at the base and form ice
          • Ice at the bottom becomes like toothpaste and moves slowly
    • Glaciers
      • Continental glaciers
      • Mountain glaciers
      • About 10% of the earth’s land is under ice
      • Glaciers change landforms by erosion
        • Scour the land as they move
      • Glaciers create landforms when they deposit debris they have transported
        • Till consists of rocks, pebbles, silt
    • Glacial Landforms
      • Erosional
        • Glacial troughs
        • Fiords
        • Tarns and cirques
        • Arêtes
      • Depositional
        • Moraines
        • Eskers
        • Drumlins
        • Outwash plains
    • Waves, Currents, and Coastal Landforms
      • Cliffs
        • Formed by wave action when land at the coast is well above sea level
      • Beaches and spits
        • Formed by the deposition of sand grains
        • Longshore currents transport sand
      • Sandbars
        • Formed by sand deposited by the backwash of waves
        • May expand to enclose lagoons or inlets
          • Salt marshes may develop
    • Waves, Currents, and Coastal Landforms
      • Coral reefs
        • Composed of coral organisms growing in shallow tropical water
        • Develop short distances offshore
      • Atolls
        • Reefs formed in shallow water around a volcano that has since been covered or nearly covered by water
    • Wind
      • Most significant in dry climates
        • Limited vegetation leaves exposed particles subject to movement by wind
      • Dunes
        • Produced by wind-driven sand
      • Loess
        • Deposit of windblown silt
        • Rich soils usually form from loess deposits
    • Landform Regions
      • Large section of the earth’s surface where a great deal of homogeneity occurs among the types of landforms that characterize it
        • Mountains
        • Plains
        • Plateaus