Lesson 2a: Plate Tectonics Part 1

Question 1

What is the Continental Drift?

Answer 1

A hypothesis that a supercontinent, consisting of all of the Earth’s landmasses, known as Pangaea, once existed. During the Mesozoic period Pangaea began to split and drift apart.

Question 2

Who proposed the Continental Drift?

Answer 2

Alfred Wegener

Question 3

When was the Continental Drift proposed?

Answer 3

1912

Question 4

What 5 pieces of evidence did Alfred Wegner use to support the continental drift?

Answer 4

1. Fit of Continents
2. Matching Rock Units
3. Distribution of Climate Belts
4. Past Glaciations
5. Distinct Identical Fossils on Continents Separated by Oceans

Question 5

Why was the Continental Drift rejected?

Answer 5

Wegener was unable to identify a credible mechanism of the continental drift.

Question 6

What is the Theory of Plate Tectonics?

Answer 6

The theory that the rigid Lithosphere overlies the Asthenosphere due to differences in physical properties; the lithosphere is detached from the asthenosphere allowing layers to move separately.

Question 7

What is the driving mechanism of Plate Tectonics?

Answer 7

Mantle convection

Question 8

What was evidence of Plate Tectonics? (5)

Answer 8

1. The ocean floor
2. Paleomagnetic Reversals
3. Ocean Drilling
4. Seismic surveys
5. Hot Spots and Mantle Plumes

Question 9

What were the key findings of the Seafloor Spreading? 3

Answer 9

1. Magma oozes up from Earth’s interior along the mid-ocean ridges, creating a new seafloor.
2. The new seafloor spreads away from the active ridge crest, and, eventually, sinks into the deep oceanic trenches.
3. Continuous spreading produces fractures in the rift valley, into which, magma from the mantle carry the continents away from the oceanic ridge, and toward deep-sea trenches

This is how the entire ocean floor is completely regenerated in 200 million years.

Question 10

What were the key findings of Paleomagnetism?

Answer 10

1. Earth’s magnetic field occasionally reverses its polarity.
2. Reversals are random
3. Reversals are not instantaneous.
4. symmetrical pattern of magnetic stripes on either side of the mid-ocean ridges.
5. When sea floor basalts dated, they were the same age at similar distances away from the ridge on each side.

Question 11

What were the key findings of oil drilling in plate tectonics?

Answer 11

1. Sediments increase in age with increasing distance from the ridge crest.
2. Sediment’s almost absent on ridge crest. Sediments thickest are furthest from the spreading center.

Question 12

What were the key findings from Seismic survey?

Answer 12

1. Sediment thicknesses were up to several thousand meters thick near the continents, and relatively thin, or even non-existant, in ocean ridge areas
2. Crust is relatively thin under the oceans compared to the continents and geologically very consistent.

Question 13

What is the Mantle Plume?

Answer 13

a cylindrically shaped upwelling (blob) of molten rock/magma.

Question 14

What is a Hot Spot?

Answer 14

A surface expression of a mantle plume in an area of volcanism

Question 15

Give an example of the mantle plume and hotspot.

Answer 15

1. Yellowstone
2. Hawaiian Islands

Question 16

What is convection?

Answer 16

A heat transfer that involves the actual movement of a substance.