Download Forces inside the Earth

Continental Drift and
Plate Tectonics
Principles of Science
Mr. Porter
Earth’s 3 Main Layers
1. Core - made of
solid iron and
nickel
3,500 km thick.
Core
Outer Core
Earth’s 3 Main Layers
2. Mantle – Mostly
solid rock, but
the top is partly
melted.
2,800 km thick.
Mantle
Earth’s 3 Main Layers
3. Crust - Top layer
of the Earth.
 Very thin, only 8
to 70 km thick.
 Continents and
ocean floor are
part of the crust.
Crust
Continental Drift
Continental drift - A theory
that states all the continents
used to be joined in 1 giant
continent called Pangea, then
they drifted apart.
1912- the German scientist,
Alfred Wegener proposed this
theory to explain why Africa
and South America could fit
together.
Continental Drift
(Additional Evidence)
1. Similar fossils were found on
different continents.
Continental Drift
(Additional Evidence)
2. Mountain ranges and rock layers seemed
to continue from continent to continent.
• Rock types in Brazil
match those in West
Africa.
• Appalachian Mtns
have limestone similar
to Scotland’s Highlands
Continental Drift
(Additional Evidence)
3. Glacial deposits found near equator.
•
South African rock formations show evidence of
ice sheet scratches
Seafloor Spreading
• Mid-oceanic ridge - long, underwater
mountain range
• discovered by scientists after WW II.
• Rift valley – A deep valley that splits the
ridge in half.
• Magma is continually coming up from within
the valley creating new sea floor crust and
pushing the old sea floor apart.
Seafloor Spreading
Plate Tectonics
Plate tectonics states that the Earth’s
crust is made up of large sections, or
plates, that are in motion.
Plates move in 3 different ways
Plate Tectonics
Plate Tectonics
1. Convergent
- Collide
with Each
other.
Plate Tectonics
2. Divergent
- Move
Apart.
Plate Tectonics
3. Transform Slide Past Each
Other.
Plate Tectonics
The pushing, pulling, and grinding of
plates cause earthquake and volcanoes.
Scientists believe convection currents
allow for plate movement.
Convection Current - circular movement
of a liquid or gas as it heats.
Plate Tectonics
Review Q’s
1) Which layer of the Earth do we stand on?
2) Which layer of the Earth is the thickest?
Thinnest?
3) List 3 pieces of evidence that support
continental drift.
4) What is Pangea?
5) How does the theory of plate tectonics
explain how the continents were moved
thousands of miles from each other?
Homework
 Continental Drift Foldable
 Take a separate sheet of paper and do a
horizontal fold (hamburger fold).
 Then take the edges and fold them back to
the spine.
 Design and color the foldable to show
how the theory of continental drift works.