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2011-03-07 21:08:01

Vocab Words for Geo 20 Midterm
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  1. Divergent Boundaries
    Where two plates are being stretched apart.
  2. Sea Floor Spread
    The divergent motion and creation of oceanic crust caused by rising magma along divergent plate boundaries, evidence includes:

    • Deep ocean floor show basaltic oceanic crust and overlying sediment which become progressively younger as the mid-ocean ridge is approached, and the sediment cover is thinner near the ridge. Second,the rock making up the ocean floor is considerably younger than the
    • continent. This confirms that older ocean crust has been reabsorbed in
    • ocean trench systems.
  3. Linear Sea
    Water in an oceanic trench?
  4. Oceanic Lithosphere Layers
    Oceanic lithosphere consists mainly of: Mafic Crust and Ultramafic Mantle, and is denser than continental lithosphere.
  5. Oceanic Ridge
    General term for an underwater mountain system that consists of various mountain ranges (chains), typically having a valley known as a rift running along its spine, formed by plate tectonics.
  6. Basaltic Volcanism
    Volcanoes are generally found where tectonic plates are diverging or converging. Mid-Atlantic Ridge, Pacific Ring of Fire
  7. Covergent Boundaries
    Boundary where two plates are forced into eachother
  8. 3 Types of Convergent Boundaries
    • Oceanic to Continental-oceanic plate is subducted due to the fact that it is more dense, which can cause volcanos and mountain building
    • Oceanic to Oceanic-subduction, causing underwater volcanoes to form
    • Continental to Continental-two continental plates collide, neither subducts into the mantle, the
    • crust is thickened, and mountain ranges are formed from the thickening
    • and uplift
  9. Subduction
    The process by which an oceanic plate is driven beneath another plate into the mantle along a convergent boundary
  10. Accretionary Wedge
    formed from sediments that are accreted onto the non-subducting tectonic plate at a convergent plate boundary. Most of the material in the accretionary wedge consists of marine sediments scraped off from the downgoing slab of oceanic crust
  11. Island Arc
    A type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates
  12. Back Arc Basin
    Geologic features, submarine basins associated with island arcs and subduction zones, result from tensional forces caused by oceanic trench rollback and the collapse of the edge of the continent
  13. Fore Arc Basin
    • A depression in the sea floor located between an accretionary wedge and a
    • volcanic arc in a subduction zone, and lined with trapped sediment.
  14. Andestic Volcanism
    In an Andestic magma contains 52–63% silica, the lava is of intermediate composition.These "andesitic" volcanoes generally only occur above subduction zones. Andesitic lava is typically formed at convergent boundary margins of tectonic plates
  15. Obduction
    Obduction occurs where a fragment of continental crust is caught in a subduction zone with resulting overthrusting of oceanic mafic and ultramafic rocks from the mantle onto the continental crust creating an ophiolite.
  16. Ophiolite
    • a section of the Earth's oceanic crust and
    • the underlying upper mantle that has been uplifted and exposed above sea
    • level and placed on the continental crust
  17. Trench
    A deep long depression in the sea floor making the surfaceof a subduction zone
  18. Docking
    Beginning of an accretion event which is a process by which material is added to a tectonic plate or a landmass. This material may be sediment, volcanic arcs, seamounts or other igneous features
  19. Sutres
    A suture is structural geology in a major fault zone through an orogen or mountain range.
  20. Accreted Terrain
    A portion of a plate added to a larger block of crust
  21. Micro Plate
    Any small lithospheric plate.
  22. Suspect Terrane
    Lithology, age, fossils, and paleomagnetic orientation of a suspect terrane may differ from its host continent.
  23. Active Continental Margins
    Passive Continental Margins
    Leading Edge Margins
    Trailing Edge Margins
    Place where the edge of a continent coincides with a plate boundary, West vs. East Coast of the US
  24. Mountain Range Types
    • Fold Mountains (Folded Mountains):
    • when two plates collide head on
    • Faultblock Mountains(BlockMountains):
    • form when faults or cracks in the earth's crust force some materials or blocks of rock up and others down
    • DomeMountains:
    • are the result of a great amount of melted rock (magma) pushing its way up under the earth crust. Without
    • actually erupting onto the surface, the magma pushes up overlaying rock layers
    • VolcanicMountains:
    • formed when molten rock (magma) deep within the earth, erupts, and piles upon the surface
    • Plateau Mountains:
    • mountains are formed by erosion. Plateaus are large flat areas next to folded mountains
  25. Transcurrent Boundary
    • A geological fault (a form of strike-slip fault) found in mid-ocean
    • ridges in which displacement undergoes a sudden change in direction
  26. Complex or Folded Mountain
    • Folded, or complex, mountains are created by intense compressional forces that fold, fault, and metamorphose the rocks,
    • resulting in many of the world's biggest mountain belts, such as the
    • Himalayas
  27. Tectonic Stress
    Causes landforms and rocks to be disrupted, creating features that geologists can uses to interpret the forces that made them
  28. Compression
    Causes rocks to crumple and buckle, reverse faults are found in areas of compression
  29. Reverse and Thrust Faults
    A fault along which one side is moved up and over the otherside as a result of compression
  30. Extension
    Stretching that occurs in response to stresses directed away from eachother
  31. Normal Fault
    A fault that drops down one side down relative to the other as a result of extension
  32. Shear Stress
    Forces causing two bodies of rock or other materials to move past eachother
  33. Strike Slip Fault or Transform Fault
    Fault with lateral motion, also a transform fault
  34. Transpression
    A combination of compression and transform motion
  35. Transtension
    A combination of extension and transform motion
  36. Deformation
    Deformation refers to the changes in volume or shape of a body of rock