READING QUESTIONS: Plate TectonicsPSCI131Winter 2017

NAME______DUE: Monday, February 6th 62 pts

Continental Drift: An Idea Before Its Time (p. 71-74)

  1. List Alfred Wegener’s four lines of evidence for continental drift: (4 pts)
  2. ______
  3. ______
  4. ______
  5. ______
  1. In the early 20th century, before continental drift, what were the three prevailing explanations for how land animals migrated across large oceans? (3 pts)
  1. ______
  2. ______
  3. ______
  1. Fill in the blanks (p. 74): “Wegener suggested that a…plausible explanation for the late Paleozoic
    ______was provided by the supercontinent of ______. In this
    configuration, the southern ______are joined together and located near the
    ______. This would account for the conditions necessary to generate extensive
    expanses of ______over much of these landmasses. At the same time, this
    geography would place today’s ______continents nearer the
    ______and account for the tropical ______that generated the vast
    ______. (9 pts)

The Great Debate (p. 75-76)

  1. What mechanism did Wegener propose for continental drift, and what objection did physicist Harold Jeffreys have to this mechanism? (4 pts)

______

______

______
______

______

______

  1. Fill in the blanks (p. 75): “Wegener…incorrectly suggested that the larger and sturdier continents
    ______the thinner oceanic crust, much as ______
    cut through ice. …No evidence existed to suggest that the ocean floor was ______enough to

permit passage of the continents without the continents being appreciably ______

in the process.” (4 pts)

The Theory of Plate Tectonics (p. 76-78)

  1. What major ocean floor feature did oceanographers discover the extent of after World War II?

______

  1. Match the name of each type of plate boundary with the arrows that show the kind of motion that occurs there. (3 pts)
  2. Transform___A.
  1. Divergent___B.
  1. Convergent___C.

Divergent Plate Boundaries and Seafloor Spreading (p. 78-81)

  1. What is the average rate of seafloor spreading in modern oceans? ______cm/year
  2. Fill in the blanks (p. 79): “The primary reason for the ______position of the oceanic ridge is
    that newly created lithosphere is ______, which means it is ______than cooler rocks
    found away from the ridge axis. (3 pts)
  3. Examine figure 15 and fill in the blanks: “Continental rifting occurs where plate motions produce
    opposing ______forces that ______the lithosphere and promote upwelling in the
    mantle. Stretching causes the brittle crust to ______into large ______that sink,
    generating a ______. Continued spreading generates a long, narrow ______similar
    to the present-day Red Sea. Eventually, an expansive ______containing
    a centrally located ______is formed by continued seafloor spreading.” (8 pts)

Convergent Plate Boundaries and Subduction (p. 81-84)

  1. Fill in the blanks: The angle at which an oceanic plate subducts depends largely on its _____ and
    therefore its ______. (2 pts)
  1. List the three possible combinations of lithosphere types that can occur at a convergent boundary. (3 pts)
  2. ______
  3. ______
  4. ______
  1. EXTRA CREDIT: List one geographic example of a modern volcanic island arc, and one example of a continental volcanic arc. Give the names of specific mountain ranges. (2 pts)
  2. Volcanic island arc: ______
  3. Continental volcanic arc: ______
  1. Oceanic lithosphere subducts because it is ______than the asthenosphere beneath it.
  1. Fill in the blanks (p. 84): “The third type of convergent boundary results when one ______
    moves toward the margin of another because of ______of the intervening seafloor.
    Whereas oceanic lithosphere tends to be ______and sink into the mantle, the ______of
    continental material inhibits it from being subducted. Consequently, a ______between two
    converging continental fragments ensues. This event ______and ______the accumulation
    of sediments and sedimentary rocks along the continental margins as if they had been placed in a
    gigantic ______. The result is the formation of a new ______composed of
    deformed ______and ______rocks.” (10 pts)

Transform Plate Boundaries (p. 85-86)

  1. On this diagram of a fracture zone along an oceanic ridge, label the segment of the zone that is an active transform boundary by marking a “T” on one of the three blanks.

  1. EXTRA CREDIT: List two examples of transform boundaries that cut through continental crust instead of through ocean basins. (2 pts)
  2. ______
  3. ______

Testing the Plate Tectonics Model (p. 89-94)

  1. What is the age of the oldest sediments recovered by deep-sea drilling? ______
  1. Continental rocks have been discovered that are older than ______years.
  2. The age of oceanic crust and the thickness of sediment on the ocean floor both ______away
    from the crests of oceanic ridges, providing strong support for the ______
    hypothesis. (2 pts)
  1. Examine figure 32A on page 93. The white stripes indicate oceanic crust exhibiting normal magnetic polarity, and the red stripes indicate reversed polarity. How many time intervals of reversed polarity are represented by the oceanic crust in this figure? (Remember that, during each time interval of reversed or normal polarity, two stripes of crust with that polarity are created along divergent boundaries.)

Number of time intervals of reversed polarity: ______