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Continental Drift
What is continental drift?
What is continental drift?
1912 Alfred Wegener
Hypothesized that• the continents are
moving
= Continental drift
• all continents once
formed a
supercontinent
= Pangaea 
How do South America and Africa fit together?
(Evidence #1) S. America’s east coast fits like
a puzzle piece with
Africa’s west coast
How do South America and Africa fit together?
(Evidence #1) S. America’s east coast fits like
a puzzle piece with
Africa’s west coast
Look at the bottom picture.
What do you notice
about the mountains
in North America
and Europe?
Look at the bottom picture.
What do you notice
about the mountains
in North America
and Europe?
The Appalachian Mtns.
(USA) and the
mountains in Europe
once formed a line
(Evidence #2) The type
of rocks in different
continents are similar
What can past climates tell us?
(Evidence #3)
Continents show past
changes in the climate
• Fossils of tropical
plants in Antarctica,
indicate a warmer,
tropical climate at
one time
• Rocks show that
glaciers once formed
on Pangaea
Where are fossils of the fern,
Glossopteris, found?
(lighter colored area below)
(Evidence #4)
Africa and South America have
the same fossils
How is the fossil evidence useful for proving
Continental Drift?
How do we know that continents are pushed apart?
(Evidence #5) Seafloor spreading
at mid-ocean ridges (1962 H. Hess)
How do we know that continents are pushed apart?
(Evidence #5) Seafloor spreading
at mid-ocean ridges (1962 H. Hess)
• Rocks made in the
Atlantic Ocean are
younger (or newer)
than the continents
Here’s how we know this• Crust furthest from the
ridge has older sea-fossils
• Patterns in iron crystals
(paleomagnetism)
indicate that ocean crust
began forming less than
160 million years ago
How many tectonic plates are there?
Scientists have identified
7 major plates and 14 smaller ones
How many tectonic plates are there?
Scientists have identified
7 major plates and 14 smaller ones
Where are volcanoes found?
Write down one thing that you notice about where
volcanoes occur
Where are volcanoes found?
Write down one thing that you notice about where
volcanoes occur
(Evidence #6) Volcanoes and earthquakes near plates
When did Pangaea break apart?
…During the Mesozoic Era, about 200 m.y.a.
Summary of evidence:
#1 Continental coastlines fit together (Wegener)
#2 The type of rocks in different continents are similar
(Wegener)
#3 Past changes in the climate can be explained by
Continental Drift (Wegener)
#4 The same plant & animal fossils are found on different
continents (Wegener)
#5 Seafloor spreading explains plate movement
#6 Volcanoes & earthquakes indicate plate movement
Handout- Continental Drift Sequence
A. Color each continent the same color in each picture
of the sequence.
B. Identify each continent and label them.
C. On the back, describe what happens with the
continents as time passes.
D. Draw a prediction of where they will be in the future.
Continents
North America
Eurasia
South America
Antarctica
Africa
India
Australia
resources
• http://www.plainedgeschools.org/swells/pl
ate_tectonics.htm
• http://slohs.slcusd.org/pages/teachers/rha
mley/Biology/Continental%20Drift/Tectonic
s.html
• http://geology.rutgers.edu/103web/Pangea
breakup/breakupframe.html
review
1Summarize Alfred Wegener’s continental drift hypothesis
2Note evidence that Wegener used to support his
hypothesis: Fit of continents, fossil evidence, rock types
& structures, climate evidence
3Why was Wegener’s hypothesis rejected by the scientific
community
4what new evidence was found to support Wegener’s
hypothesis 2pts
5how does the new theory of plate tectonics explain
continental drift
6make a sketch to show how divergent plate boundaries
are formed
7paleomagnetism
What is continental drift?
1912 Alfred Wegener
Evidence shows that• the continents are
moving
= Continental drift
• all continents once
formed a
supercontinent
= Pangaea
What pushes continents apart?
Mid-ocean ridges, AKA seafloor spreading
(1960 H. Hess)
• Seafloor mountains
with a steep, narrow
valley running down
its center
• Crust near the ridge
is very young
• Crust furthest from
the ridge is oldest
How do we know that continents are pushed apart?
(Evidence #5) Seafloor spreading
at mid-ocean ridges (1962 H. Hess)
• Ocean rocks are
younger (or newer) than
continental crust
Here’s how we know this• Crust furthest from the
ridge has older sea-fossils
• Patterns in iron crystals
(paleomagnetism)
indicate that ocean crust
began forming less than
160 million years ago