Continental Drift
and Plate Tectonics
Alfred Wegener
1880-1930
● German scientist
● Introduced the Theory of
Continental Drift in his book
The Origin of the Continents
and Oceans (1915)
● Many scientists had noticed
the remarkable fit of the
coastlines of South America &
Africa
● First to use geological and
paleontological evidence to
show these continents were
once joined
Evidence of Pangaea
Theory of Continental Drift
• Proposed by Wegener in 1915
• Used evidence from climate, fossils and
landforms to match up the continents
• All of the continents were once joined in one
large supercontinent called Pangaea and have
since drifted apart
• Wegener did not have a force to provide the
movement so it was not accepted until the 1950’s
● Wegener spent much of his life defending his theory
Wegener’s Continental Drift
http://www.ucmp.berkeley.edu/geology/anim1.html
225 million years ago all
continents connected in
one land mass called
Pangaea
180-200 million years
ago Pangaea separated
into Laurasia and
Gondwanaland
135 million years ago
Laurasia and
Gondwanaland began to
separate into continents
65 million years ago the
continents move even
further apart
The position of the
continents on Earth
today
Untold
Tragedies of
Continental
Drift
The Crust
• This is where we live!
• The Earth’s crust is made
of:
Continental Crust
Oceanic Crust
- thick (10-70km)
- buoyant (less dense
than oceanic crust)
- mostly old - granite
- thin (~7 km)
- dense (sinks under
continental crust)
- Young - basalt
Earth’s Interior
• Lithosphere: Area
of the crust and the
upper mantle.
– Crust:
• Outer most layer
• Continental crust
(less dense
granitic)
• Oceanic crust
(more dense
basaltic)
• Asthenosphere:
– Rocks are at or near
melting point
– Exhibits plasticity – a
solid that flows like a
liquid
Assignment
In your spiral – draw and color a picture of the Earth’s
interior, labeling the following:
Wegener’s Puzzling Evidence
1. Label the land masses on each sheet. Color the
fossil areas to match the legend below.
2. Cut out each of the continents along the edge of
the continental shelf (the outermost dark line).
Alfred Wegener's evidence for continental drift is
shown on the cut-outs. Wegener used this
evidence to reconstruct the positions of the
continents relative to each other in the distant
past.
3. Try to logically piece the continents together so
that they form a giant supercontinent.
India
Antarctica
S. America
Africa
Australia
Plate Tectonics
• Proposed in 1960’s by a variety of scientists
including Hess, Dietz and Vine
• Suggests that the lithosphere is broken up into
many plates which are moving around the earth
in different directions
• All of the continents were once together in one
supercontinent – Pangaea
• Movement is caused by convection currents in
the mantle of the Earth
• Explained the cause of earthquakes, volcanoes,
mountain building
Plate Tectonics
• Plate Tectonics: Theory that the Earth’s
lithosphere is broken into plates and float
on the asthenosphere
• Convection Currents: Drives plate motion
– hot magma rises from core, cools and
sinks back to core – cycle starts over
(think of a lava lamp)
Double Bubble
• Make a double bubble map of Continental
Drift and Plate Tectonics
CONCLUSION
• Imagine you are Alfred Wegener in 1915.
Write a Claim – Evidence – Reasoning
about your theory of Continental Drift.
• Use the evidence from the lab we just
completed. Your reasoning you can come
up with on your own (Remember it is 1915
and you are Wegener)
CER Peer Editing
• Claim – All continents were once joined together and
have since drifted apart = 20pts
Is it a complete logical sentence = 10pts
• Evidence – Must mention at least 2 of the following:
Dinosaur Fossils, Plant Fossils,
Landforms (the way they fit together) = 30 pts
Is it a complete sentence? = 10pts
• Reasoning – Does it make sense? = 20 pts
Is it a complete sentence? = 10pts
Write the totals in the box at the bottom of the page