Plate Tectonics Theory & More

Question 1

Evidence For Change:

Answer 1

• Deformed strata (layers of rock)
• Seismic activity
• Subsidence or sinking of the crust (Gulf of Mexico)
• Uplift of the crust (mountains)

Question 2

Discoveries Leading Up to the Theory of Plate Tectonics:

Answer 2

• Continental Drift
• Sea floor spreading
• Paleomagnetic Data and Polar Wandering

Question 3

Continental Drift Theory:

Answer 3

• Proposed by German scientist Alfred Wegner in 1915
• States that all continents were originally one land mass called Pangea
• Was a radical theory at the time

Question 4

Supportive Evidence for Continental Drift:

Answer 4

• Fit of coast lines
• Matching fossil evidence
• Matching paleoclimates
• Matching rock and mineral type and structural similarities

Question 5

Strengths of Continental Drift:

Answer 5

• Continents do really seem to fit together like a giant puzzle
• Matching evidence from either side of Atlantic Ocean in Africa and South America of fossil remains, rocks, minerals and paleoclimates…

Question 6

Weakness of Continental Drift:

Answer 6

Wegner could not explain how or why continents moved…

Question 7

Sea Floor Spreading:

Answer 7

Harry Hess from Princeton University proposed that sea floor is spreading apart. This spreading was thought to be caused by convection currents in the mantle (1962)

Question 8

Magnetic Reversals on Seafloor:

Answer 8

• Pattern of magnetic polar reversals found on sea floor in 1963
• Connects to idea of sea floor spreading by Harry Hess
• Reversals coincide with age of rock on sea floor

Question 9

Polar Wandering Data:

Answer 9

Mid 50’s scientists produce paleomagnetic data from several continents showing the apparent polar wandering consistent with Wegner’s theory (magnetic north poles changed position over time)

Question 10

Unified Theory of Plate Tectonics:

Answer 10

• All previous ideas can be explained by this theory

- Term “Plates” was coined in the 1960’s by J. Tuzo Wilson of the University of Tornto

Question 11

Main Points of the Unified Theory of Plate Tectonics:

Answer 11

• Surface of the Earth is composed of major rigid moving sections called “plates”
• These plates float on the mantle
• The plates consist of continental and oceanic rock
• The boundary where plates meet is the area of the most crustal activity
• Differences in the density of materials in the asthenosphere move the plates

Question 12

Three Types Of Plate Motions:

Answer 12

Convergent
Divergent
Transform

Question 13

Convergent:

Answer 13

Move together

Question 14

Divergent:

Answer 14

Seperate

Question 15

Trasnform:

Answer 15

Slide past