Transcript Plate Tectonics - drakepond8thgradescience / FrontPage

Plate Tectonics
plate tect BN.asf
• Wegener’s theory of continental drift was not
accepted because he did not have a good
explanation or mechanism for how it worked.
He used…
1. The fit of the continents
• The continents fit like
puzzle pieces.
2. Fossils
• Fossils of the same
dinosaur were found on
different continents
(South America and Africa).
• Fossils of the same
plant were found in
many different locations
(Africa, Australia, India, South
America and Antarctica).
3. Past Climate Conditions
• Fossils of warm weather
plants were found in
cold locations (like the
Arctic Ocean)
• Evidence of glacial
activity can be found in
South America, Africa,
India, and Australia.
4. Rocks and Common Geologic
Features
- Similar rock structures
can be found in
Greenland and the
eastern U. S. and also in
South America and
Africa.
Plate Tectonics
• Developed around 1950 to explain the motion
of the plates and the position of the
continents.
• Further evidence was identified to support
Wegner’s theory and a mechanism was
discovered to explain how/why the plates
move.
1. Seafloor Movement
• New land is added on
the sea floor at
divergent boundaries
and as a result, the sea
floor spreads apart.
– (Mid-ocean Ridges form
at these divergent
boundaries)
http://www.suu.edu/faculty/colberg/Hazards
/PlateTectonics/30_SeaFloor.html
2. Age of rocks on the ocean floor
• Rocks near the midocean ridges are
younger than those
farther away
3. Paleomagnetism
• Over time the Earth’s
magnetic poles have
reversed.
• When the poles reverse,
iron minerals align
themselves with the
Earth’s magnetic pole.
• Scientists have found
rocks on the ocean floor
that showed many
magnetic reversals.
4. Locations of hot spots
• Hot spots are stationary
• Scientists can track the
movement of a plate by
looking at the position
of a hot spot.
• http://www.suu.edu/faculty/colberg/Hazards/
PlateTectonics/18_Pangaea.html