Transcript Continental Drift and Plate Tectonic

Theory of Continental Drift
and
Theory of Plate Tectonics
* Essential Questions *
What were points of contention with
the Theory of Continental Drift?
How did the Theory of Plate Tectonics
affirm the Theory of Continental Drift?
Warm Up:
What information
can you gather
from the
Mosquito Creek
cartoon?
Mosquito Creek
Theory of Continental Drift
• Proposed by Alfred
Wegener
• States that the
continents were
once joined to form
a supercontinent
• Named the
continent Pangaeaall land
Continental Drift
• Supporting
evidence
– Continental
Puzzle
– Matching Fossils
– Rock Types and
Structures
– Ancient Climates
Continental Drift
• Continental Puzzle
– Similar coastlines
on opposite sides
of South Atlantic
Ocean
• Counter Argument
– Similar coastlines
due to erosion
Continental Drift-Evidence
• Matching fossils
– Fossils of same
species found on
different continents
– Exp. Mesosaurus
found in South
America & Southern
Africa
• Counter Argument
– Land bridges which
occurred during glacial
period
Continental Drift-Evidence
• Rock Types &
Structures
– Mountain belts
occur on multiple
continents
– Exp. Appalachian
Mountains
Continental Drift-Evidence
• Ancient Climates
– Glacial evidence in
southern Africa and
South America
– Large tropical swamps
in Northern
Hemisphere
• Coal fields in eastern
US, Europe, and Siberia
• Counter Argument
– Earth was very cold
Continental Drift
• Major problem
– No mechanism of
continent movement
– Hypothesis rejected
Plate Tectonics
• Mechanism of
continent movement
• Solution came from
seafloor mapping data
• States: Earth’s crust is
divided into distinct
plates that float on
molten interior ->
continents move as
plates move
Plate Tectonic Theory
• 13 different plates
• Supporting
Evidence
– Paleomagnetism
– Earthquake
Patterns
– Ocean Drilling
– Hot Spots
Plate Tectonic Theory-Evidence
• Paleomagnetism
– Rocks containing ironrich minerals are
magnetized
– Point towards the
magnetic pole of
creation
– Strips of alternating
polarity occur at
ocean floor -> seafloor
spreading
Plate Tectonic Theory-Evidence
• Earthquake Patterns
– Along ocean trenches
1. Shallow focused
earthquakes occur
within trench/where
descending plate
interacts with
lithosphere
2. Deep focused
earthquakes occur
toward mainland/
when oceanic
lithosphere plunges
into mantle
Plate Tectonic Theory-Evidence
• Ocean Drilling
– Sediment closer to
ridges will be
younger
– Sediments farther
away will be older
4
3
2
1
Sediment age
increasing
1
2
3
4
Sediment age
increasing
Plate Tectonics-Evidence
Plate Tectonic Theory-Evidence
• Hot Spots
– Rising plume of
mantel material
– Melting of rock
at/near surface ->
volcanics
– Plate moves
creating successive
volcanic
mountains/chains
Recap
1. The Theory of Continental Drift explains
movement of continents over time
2. Theory of Plate Tectonics provides mechanism
for movement.
3. Supporting evidence:
C-Drift
P-Tectonics
Continental Puzzle
Paleomagnetism
Matching Fossils
Earthquake Pattern
Rock Types and
Structures
Ancient Climates
Ocean Drilling/Ages
Hot Spots