ESC 1000

1
ESC 1000

• CH 3
• Plate Tectonics

2
Theory of Plate Tectonics

• 1960s
• Evidence
• Observation/mapping of erupting volcanoes and
  earthquakes
• Sea floor mapping
• Geologic features
• Mid ocean ridge
• Deep ocean trenches
• Coastlines and continental shelves matching up

3

• Paleomagnetism magnetism in rocks
• Normal polarity
• Reverse polarity
• Polar wandering curves
• Paleomagnetism and Seafloor spreading

4

• Rock Record
• Sedimentary rock types, reveals paleoclimates
• Correlation of rock type and age, fossils

5
Plate Boundaries

• 3 distinct types
• Divergent plate boundary
• Transform plate boundary
• Convergent plate boundary

6
Divergent Plate Boundary

• Lithospheric plates move apart, magma wells up
  from the asthenosphere and new lithosphere is
  created
• Common in oceanic plates
• Oceanic example Mid-Atlantic Ridge
• Continental example East African rift valley

7
Transform Plate Boundary

• Associated with divergent plate boundaries
• Earthquakes common along these boundaries.
  Exceeding elastic limit of the rock
• Ex San Andreas

8
Convergent Plate Boundary

• Plates moving toward each other, colliding
• Different collisions result from different types
  of plate material
• Continental/continent
• Oceanic/continental
• Oceanic/oceanic

9
Continent/Continent collision

• two thick landmasses collide, crumple and deform
• Neither one sinks deeply into the mantle
• Extreme deformation and uplift occurs
• Ex Himalayas

10
Oceanic/Continental

• Denser oceanic plate is subducted or carried down
  beneath the lighter continental plate (subduction
  zone)
• Subduction zone
• Area of high geologic activity
• Great stresses involved
• Sea floor is being subducted (destroyed)
• Melted material rises back up through the
  overlying plate and creates volcanoes
• Deep oceanic trenches associated with this
  boundary
• Ex Cascade Range/ Andes Mountains

11
Oceanic/Oceanic collision

• One plate is carried below into the
  asthenosphere, heated, melts and returns to the
  surface created volcanic island arcs
• Volcanic island arcs
• Volcanic islands that arise from the sea floor,
  denser, mafic basalt (oceanic crust material)
• Less explosive eruptions, more flowing type
• HOT SPOT isolated area of volcanic activity,
  not associated with plate boundary

12
Plate Tectonics Rock Cycle

• At subduction zones, seafloor material is being
  destroyed and constantly being created at
  spreading zones.
• Maintains balance of oceanic material