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GEOG101 Chapt03 lecture
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GEOG101 Chapt03 lecture


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  • 1. Overview
    • Earth Materials
    • Geologic Time
    • Movements of the Continents
    • Tectonic Forces
    • Gradational Processes
    • Landform Regions
  • 2. Earth Materials
    • Igneous Rocks
    • Sedimentary Rocks
    • Metamorphic Rocks
  • 3. 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
  • 4. 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
  • 5. 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
  • 6. 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
  • 7. 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
  • 8. 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
  • 9. 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
  • 10. 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
  • 11. 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
  • 12. Gradational Processes
    • Reduction of the land’s surface
      • Weathering
      • Mass movement
      • Erosion
  • 13. 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
  • 14. 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
  • 15. 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
  • 16. 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)
  • 17. 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
  • 18. 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
  • 19. 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
  • 20. 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
  • 21. 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
  • 22. Glacial Landforms
    • Erosional
      • Glacial troughs
      • Fiords
      • Tarns and cirques
      • Arêtes
    • Depositional
      • Moraines
      • Eskers
      • Drumlins
      • Outwash plains
  • 23. 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
  • 24. 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
  • 25. 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
  • 26. 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