Chapter 3 Land


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  • 6.6 magnitude; occurred on the Bam fault, and was caused by northward motion of the Arabian plate against the Eurasian plate; death toll has reached 41,000 ; worst recorded disaster in Iranian history
  • Chapter 3 Land

    1. 1. CHAPTER 3 Landforms
    2. 2. <ul><li>Study of the landforms and the processes that create them </li></ul>Geomorphology
    3. 3. Important Points <ul><li>Study of the Lithosphere </li></ul><ul><li>Elements of surface have identifiable forms are called landforms </li></ul><ul><ul><li>Mountains </li></ul></ul><ul><ul><li>Plains </li></ul></ul><ul><ul><li>Plateaus </li></ul></ul><ul><ul><li>Valleys </li></ul></ul><ul><li>Landforms constantly change </li></ul><ul><li>Geographers study topography (shape of the earth’s surface) </li></ul>
    4. 4. Processes that create landforms <ul><li>Endogenic Processes </li></ul><ul><ul><li>Internal Forces </li></ul></ul><ul><ul><li>Earthquakes </li></ul></ul><ul><ul><li>Volcanoes </li></ul></ul><ul><li>Exogenic Processes </li></ul><ul><ul><li>External Forces </li></ul></ul><ul><ul><li>Erosion </li></ul></ul><ul><ul><li>Weathering </li></ul></ul>
    5. 5. <ul><li>Alfred Wegener </li></ul><ul><li>Theorized in 1912; proven after WWII </li></ul><ul><li>12 large tectonic plates float on the mantle </li></ul><ul><li>200 million years ago, all one continent (Pangaea) </li></ul>Plate Tectonics
    6. 6. Ring of Fire
    7. 8. Types of Boundaries <ul><li>Divergent boundaries </li></ul><ul><ul><li>Spread Apart </li></ul></ul><ul><ul><li>Generally mid-ocean; causes sea floor spreading </li></ul></ul><ul><ul><li>Underwater volcanoes, few quakes </li></ul></ul><ul><li>Convergent boundaries </li></ul><ul><ul><li>Push together </li></ul></ul><ul><ul><li>Usually near continental edges </li></ul></ul><ul><ul><li>Violent volcanoes near ocean, strong quakes </li></ul></ul><ul><li>Transform boundaries </li></ul><ul><ul><li>Grind together </li></ul></ul><ul><ul><li>No volcanoes, mild to strong quakes (San Andreas) </li></ul></ul>
    8. 12. Earthquakes <ul><li>Crust movement where plates meet </li></ul><ul><li>500,000 per year; 800 felt </li></ul><ul><li>Seismic waves of energy (vibrations) </li></ul><ul><li>Seismograph measures waves </li></ul><ul><li>Earthquakes don't kill people, buildings (and gas mains) do </li></ul>Epicenter – point on the surface directly above the focus of an earthquake
    9. 14. Bam, Iran 12/26/2003
    10. 15. San Andreas “ San Francisco” M8.5 – April 18, 1906, 3,000 deaths $400 million in damage
    11. 16. Rock Formation <ul><li>Types </li></ul><ul><ul><li>Igneous – molten rock cools; basalt </li></ul></ul><ul><ul><li>Sedimentary – rocks eroded from mountains; shale </li></ul></ul><ul><ul><li>Metamorphic – exposed to heat/pressure and compressed; marble & slate </li></ul></ul><ul><li>Minerals (specific chemical compounds) </li></ul><ul><ul><li>Sima – Dense w/silicon & magnesium; ocean floor </li></ul></ul><ul><ul><li>Sial – Less dense w/silicon & aluminum; makes up crust </li></ul></ul>
    12. 17. Stress on Rocks <ul><li>Fault - a break in Earth’s crust where slabs of crust slip past each other. </li></ul><ul><li>They usually occur along plate boundaries where the forces of plate motion compress, pull, or shear the crust so much that the crust breaks. </li></ul>
    13. 18. Normal fault <ul><li>The fault is at an angle, so one block of rock lies above the fault while the other block lies below the fault. </li></ul><ul><li>Found near a divergent plate boundary </li></ul>
    14. 19. Reverse Faults <ul><li>Compression produces reverse faults. </li></ul><ul><li>It is like a normal fault but the blocks move in the opposite direction. </li></ul><ul><li>Near convergent boundaries </li></ul>
    15. 20. Reverse Fault - Appalachian Mountains
    16. 21. Strike-slip fault <ul><li>Strike-slip fault - shearing causes these faults. Rocks on either side of the fault slip past each other sideways with little up-or-down motion. They also form transform boundaries . </li></ul><ul><li>Example - San Andreas fault </li></ul>
    17. 22. Mountain Building <ul><li>Over millions of years, fault movement can change a flat plain into a towering mountain range. </li></ul><ul><li>Mountains Formed by Faulting When normal faults uplift a block of rock, a fault-block mountain forms. </li></ul>Teton Range near Wyoming and Idaho was formed this way.
    18. 23. Mountains Formed by Folding <ul><li>Have you ever skidded on a rug that wrinkled up as your feet pushed it across the floor? </li></ul><ul><li>Folds - bends in rock that form when compression shortens and thickens part of Earth’s crust. </li></ul>
    19. 24. Mountains caused by Folding <ul><li>Himalayas </li></ul><ul><li>Alps </li></ul>
    20. 25. Volcanoes <ul><li>Pressure on molten rock </li></ul><ul><li>Shield volcanoes </li></ul><ul><ul><li>Made of basalt </li></ul></ul><ul><ul><li>More calm and constant (runny lava) </li></ul></ul><ul><ul><li>Along divergent boundaries or at hot spots </li></ul></ul><ul><ul><li>Relatively less dangerous </li></ul></ul><ul><li>Composite volcanoes </li></ul><ul><ul><li>Violent and explosive (lava & ash) </li></ul></ul><ul><ul><li>About 600 active (1000s dormant) </li></ul></ul><ul><ul><li>Relatively hard to predict </li></ul></ul><ul><ul><li>Can cause major climate changes </li></ul></ul>Mauna Loa Shield Volcano
    21. 26. Mt. St. Helens 5/18/1980 Composite cone volcano
    22. 27. Exogenic Forces <ul><li>Reshape the Earth’s crust into new landforms </li></ul>
    23. 28. Weathering <ul><li>Process of breaking down rocks into pieces </li></ul><ul><li>First step in the formation of soil </li></ul><ul><li>Most mountains are going down faster than they’re going up </li></ul><ul><li>Mechanical weathering breaks rocks into smaller pieces </li></ul><ul><ul><li>Frost action </li></ul></ul><ul><ul><li>Salt crystals </li></ul></ul><ul><ul><li>Roots </li></ul></ul><ul><ul><li>Exfoliation </li></ul></ul><ul><li>Rock chemistry does not change </li></ul>
    24. 29. Frost Action
    25. 30. Weathering <ul><li>Chemical weathering changes the chemistry of rocks </li></ul><ul><ul><li>Oxidation (exposure to oxygen) </li></ul></ul><ul><ul><li>Hydrolysis (exposure to water) </li></ul></ul><ul><ul><li>Carbonation (exposure to carbon dioxide) </li></ul></ul><ul><li>Warmth and water encourage chemical reactions </li></ul><ul><li>Weathering loosens rock particles, creates soil </li></ul>
    26. 31. Oxidation
    27. 32. Carbonation: Karst Formed by the dissolution of soluble rocks Karst regions contain aquifers that are capable of providing large supplies of water.
    28. 33. Erosion & Deposition <ul><li>Erosion carries particles away </li></ul><ul><li>Surface Erosion – water carrying particles </li></ul><ul><ul><li>Rainfall </li></ul></ul><ul><ul><li>Relatively slow </li></ul></ul><ul><li>Running water </li></ul><ul><ul><li>Constant water, floods </li></ul></ul><ul><ul><li>Most important landform agent in deserts </li></ul></ul><ul><ul><li>Floodplains, levees, and deltas </li></ul></ul><ul><li>Deposition deposits them </li></ul>
    29. 34. Streams are vital geologic agents <ul><li>Carry most of the water that goes from land to sea (groundwater & overland flow) </li></ul><ul><li>Transport billions of tons of sediment to the ocean each year </li></ul><ul><li>Transport billions of tons of soluble salts to the oceans each year </li></ul><ul><li>Shape the surface of the Earth </li></ul>
    30. 35. Stream Flow Some of the consequences of natural stream flow present engineering and social challenges with which we grapple year after year, and have through civilization’s history. The flow of fresh water in channels on the Earth’s surface has been essential to the development of topography and most ecosystems.
    31. 36. Floodplain Delta Levee flat or nearly flat land adjacent to a stream or river that experiences occasional or periodic flooding deposit at the mouth of a river is usually roughly triangular in shape river's banks are built up above the level of the rest of the floodplain Meander
    32. 37. These are satellite images before and during Summer, 1993 floods of the Mississippi river north of St.Louis. Mississippi Floodplain
    33. 38. Alluvial fan fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads
    34. 39. Streams Locked in Valleys Streams like these (and the Potomac River at Great Falls) have virtually no (normal) floodplains. They have carved into rock so deeply, that their meandering and other characteristic evolutionary features are restricted.
    35. 40. Glaciers <ul><li>Rivers of ice </li></ul><ul><li>Types </li></ul><ul><ul><li>Alpine Glaciers – snow accumulation over years </li></ul></ul><ul><ul><li>Continental Glaciers – covers vast areas </li></ul></ul><ul><li>Carve out landforms from mountains </li></ul><ul><li>Deposit material when they leave </li></ul><ul><ul><li>Moraines </li></ul></ul><ul><ul><li>Outwash plain </li></ul></ul><ul><li>Past 200 years has seen glacial shrinking </li></ul>
    36. 41. Glacial landforms Outwash Plain- large volumes of rock and dirt debris that often spreads out in a great sheet Terminal Moraine - accumulation of boulders, stones, or other debris carried and deposited by a glacier Alaska Long Island, NY
    37. 43. Glacial landforms: California
    38. 44. <ul><li>Iowa is almost entirely covered by loose sediments left behind by the continental glaciers which has created fertile soil </li></ul>Glacial landforms: Iowa
    39. 45. Waves and coastlines <ul><li>Waves transfer energy through wind </li></ul><ul><li>Energy moves particles down the coast (longshore current) </li></ul><ul><li>Newer coastline=erosion </li></ul><ul><li>Older coastline=deposition </li></ul><ul><li>Tsunami – extremely long wave created by earthquake </li></ul><ul><li>Barrier reef: only organically formed landform </li></ul>
    40. 46. Longshore current Pacific Palisades Longshore currents affect shorelines by redistributing sand and sediment along their path.
    41. 48. Erosion vs. deposition Acapulco Cancún
    42. 49. Great Barrier Reef