Global Tectonics: Plates and Plumes

Question 1

How does continental drift relate to plate tectonics?

Answer 1

Wegner saw the continents as a jigsaw puzzle that fit together into a prior single supercontinent, Pangea, surrounded by the sea Panthalassa

Question 2

The earth is made up of what 3 layers?

Answer 2

• core
• mantle
• crust

Question 3

The crust:

Answer 3

• Is where we live

Question 4

The Earth’s crust is made of:

Answer 4

• Continental and Oceanic crust

Question 5

Continental crust

Answer 5

• 10-70km thick
• Buoyant (less dense than oceanic)
• Mostly old

Question 6

Oceanic Crust

Answer 6

• Thin (~7km)
• Dense (sinks under continental crust
• Young

Question 7

How many plates is the earths crust divided in to?

Answer 7

The earth is divided into 12 major plates which are moved in various directions

Question 8

What does the word tectonic refer to?

Answer 8

It refers to the deformation of the crust as a consequence of plate interaction

Question 9

Plates are made of:

Answer 9

rigid lithosphere

Question 10

What lies beneath the tectonic plates?

Answer 10

• The asthenosphere

Question 11

The lithosphere makes up:

Answer 11

The tectonic plates

Question 12

Plate Movement

Answer 12

Plates of lithosphere are moved around by the underlying hot mantle connection cells

Question 13

Plate Tectonic Theory

Answer 13

• Strong lithospheric plates move atop the weaker, plastic asthenosphere
• Deformation occurs at or near the edges of plates where they interact with other plates
• The interiors of the plates are relatively undeformed

Question 14

Three types of plate boundary:

Answer 14

• Divergent
• Convergent
• Transform

Question 15

Divergent plate boundaries

Answer 15

• Show the creation of new oceanic lithosphere from the upwelling mafic magmas as well as a widening of the ocean basin
  Eg.) Iceland is an example of a mid-ocean ridge exposed above sea level - widening at the rate of ~4 mm/year

Question 16

Convergent Boundaries

Answer 16

Three types:

• Continent-oceanic crust collision
• Ocean-ocean collision
• Continent-continent collision

Question 17

Oceanic-continental boundary

Answer 17

• Much of the western boundary of South America is this type of boundary.
• Denser oceanic lithosphere flexes under the less dense, much older, continental crust.
• When oceanic and continental plates converge, the oceanic plate must subduct beneath the continental plate because the density of thick continental crust is too low to permit it to sink into the asthenosphere

Question 18

Oceanic-oceanic boundary

Answer 18

• When a convergent boundary forms between plates of oceanic lithosphere, the plate that is older, thicker, and denser subduct the less dense plate.
• Several areas of the western Pacific typify this boundary, such as the area around Japan

Question 19

How is a Subduction Zone formed?

Answer 19

They are formed when two oceanic plates collide. One runs over the other which causes it to sink into the mantle

Question 20

Continental-continental boundaries

Answer 20

When subduction brings two continents together limited subduction may occur, but the buoyancy of continental crus eventually stops the subduction. The contraction of crust in the collision zone doubles the thickness of continental crust and creates high mountains.

Question 21

Volcanoes are formed by:

Answer 21

• Subduction
• Rifting
• Hotspots

Question 22

Hotspots

Answer 22

• Form where narrow columns (plumes) of unusually hot mantle convectively rise from the core-mantle boundary
• They leave tracks on moving plates.

Question 23

Plumes

Answer 23

are an upwelling of abnormally hot rock within earths mantle. They are stationary in the mantle and other data indicates that they move slowly, if at all