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2010-04-13 00:14:01

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  1. What environments would most likely consist of sand and/or rounded cobbles?
    beach, lagoons, coastal dunes, tidal flats, submarine deltas, barrier islands
  2. What are the processes of physical weathering?; chemical weathering?
    • Physical Weathering: Near-Surface Fracturing: break rock into smaller pieces, rocks pulling away from a steep cliff, fractures also when rocks expand as they are uplifted towards the surface and progressively exposed to less pressure Frost and Mineral Wedging: can be broken as water freezes and expands, ice melting, crystals of salt and other minerals Thermal Expansion: wildfire and sun expand rocks and crack them, Biological Activity:
    • Chemical Weathering: Dissolution: soluble in water, Oxidation: some minerals w iron are unstable when exposed to Earth’s atmosphere- combine w oxygen to form oxide minerals (rusty metal) Hydrolysis: silicate minerals exposed to water converts to clay minerals and leftover material (clay-rich soils) Biological Reactions: Decaying plants, bacteria
  3. What environments create angular clasts? Rounded clasts?
    • Rounded clasts: during transport, tumbling, collisions, and abrasion
    • Angular clasts: clasts near their source
  4. Distinguish between poorly an well sorted
    • Poorly sorted: contains a wide range of clast sizes
    • Moderate Sorting: sand and small pebbles, silt or clay
    • Well sorted: clasts that all have the same size
  5. Describe the processes by which sediment is turned to rock
    Sediment is converted into sedimentary rock through lithification that involves compaction by overlying sediment and cementation by calcium carbonate or other materials, ultimately producing clastic sedimentary rock.
  6. What is he main difference between conglomerate and breccia
    Conglomerate has rounded clasts. Breccia has angular clasts.
  7. How does gypsum form
    Gypsum forms when seawater evaporates in tidal flats and narrow seas
  8. What type of rock would form from swamp sediments
    Peat, it forms through the accumulation of plant material.
  9. How does a cross bed form
    When sand and silt move over a dune or underwater ripple, grains accumulate in thin beds on the down-current side of the dune or ripple. They are at an angle to other beds in the same rock.
  10. Describe the characteristics of a transgression; regression
    • Transgression: Seas advance across a region, covering more land with time, due to either a rise in sea level or a lowering of the land. When the sea advances over land shoreline deposits are overlain with sediments tat represent areas farther offshore.
    • Regression: When the sea retreats and more land is exposed. It occurs when sea level becomes lower or the land is uplifted.
  11. Name the types of faults
    Dip: inclined, if water is poured it will flow directly down the fault. The water is flowing down the dip of the fault surface. Strike: if water floods the area, it will intersect, or strike the surface along a horizontal line. The direction of the inclined surface is the strike. Dip-Slip Fault: slip along a fault can be parallel to the dip- one block moves up or down relative to the other block. Strike-Slip Fault: slip occurs in a horizontal direction. The right slips horizontally back relative to the left block. Oblique-Slip Fault: oblique direction
  12. Distinguish between brittle and ductile deformation and explain where each is likey to occur in the crust
    • Brittle deformation is how rocks respond to stress by flowing like toothpaste squeezed from a tube. It occurs at cool shallow levels of the crust.
    • Ductile deformation is how rocks respond to stress by flowing as a weak solid. It occurs at deeper levels where temperature and pressure are higher.
  13. Explain what syclines, anticlines, domes and basins are
    • Synclines: the rock layers warp up in the shape of an A, oldest rocks are at the center of the fold
    • Anticlines: rocks fold down in the shape of a U or a V, youngest rocks are at the center of the fold
    • Domes: layers that are uplifted in a circular or elliptical area and dip away in all directions. Erosion exposes deeper and older rocks in the center of this dome.
    • Basins: Formed by folding. Opp of dome layers dip towards the center of the basin from all directions. The center of the basin preserves younger layers than surrounding areas.
  14. Match the following with their metamorphic equivalants
    • Basalt: Greenstone, Greenschist
    • Shale: Slate, Phyllite, Schist, Gneiss
    • Sandstone: Quartzite, Coarse Quartzite
    • Limestone: Finely Crystalline Marble, Impure Marble, Coarse Marble
  15. What rocks can or cannot become metamorphic
    Sedimentary and Igneous rocks can become metamorphic. Rocks where temperature and pressure are very low cannot become metamorphic.
  16. Explain what a radioactive half life represents
    A radioactive half-life represents the amount of time it takes for the parent atoms of a rock to decay into the daughter product. There will be an equal amount of parent and daughter atoms.
  17. Geologic time Scale
    Cenozoic, Mesozoic, Paleozoic, Precambrian
  18. What is the Precambrian
    Precambrian comprises nearly 90% of geological time. For most of this time only simple life forms existed, such as bacteria and algae that formed stromatolites.
  19. What is disconformity. How could you identify one?
    If rock layers are not tilted before they are overlapped by younger layers, but the boundary still represents millions of years of time, the contact is a disconformity. A disconformity can involve erosion or just a long time period with little or no deposition. Parallel to rock layers.
  20. How are the main Geologic eras defined; how were the boundaries chosen
    The timescale was devised by using fossils or by noting the absence of fossils. Later Geologists and chemists assigned numeric ages to the timescale by using carefully calculated isotopic ages at key localities
  21. What was the Cambrian explosion
    the period of rapid evolutionary change when many new shelled organisms appeared on Earth over a period of 20 to 30 million years ago
  22. What causes magnetic stripes o the seafloor
    rocks that form in the magnetic field will acquire a reversed polarity, rocks forming all along the axis of the mid-ocean ridge will have the same magnetic direction, forming the stripe
  23. Where would the thinnest & thickest cover of sediment be in the oceans
    The thinnest cover of sediment would be in the rivers. The thickest cover would be along the continental margin and near the mouths of rivers or where the oceanic crust is relatively old.
  24. Where are the deepest & shallowest parts of the seafloor
    the deepest parts of the seafloor is at the trenches along active margins where one plate subducts beneath another plate. The shallowest parts of the seafloor are on continental shelves.
  25. Which parts of the seafloor have the youngest oceanic crust? Oldest?
    youngest oceanic crust is near mid-ocean-ridge spreading centers. The oldest oceanic crust is the most distant from mid-ocean ridges.
  26. What are most oceanic islands and seamouns made of
    are made of mafic (basalt) to intermediate (andesite) volcanic rocks and are formed by a series of volcanic eruptions onto the seafloor.
  27. Where are you most likely to find a coral reef
    Most of the coral reefs are in tropical waters, near the equator, between latitudes of 30° north and 30° south
  28. How do most sea deposits form
    Many salt deposits form when seawater evaporates, leaving behind a residue of salt that was dissolved in the water
  29. What controls the regiona elevations of the crust on land
    elevations are controlled primarily by the thickness of the crust, but they can also be influenced by the temperature and density of materials in the crust and upper mantle
  30. What is the main cause of uplift during a continental collision
    A continent generally is too buoyant to be subducted deeply, so one continent is shoved beneath the edge of the other continent, and the whole region is uplifted
  31. What are hot spots and where are some located in the U.S
    Hot spots are volcanic areas interpreted to be above rising mantle plumes. Yellowstone, Snake River Plain, The basin and Range Province of Utah and Nevada are examples