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
Many pieces of evidence suggest that Pangaea existed…
How do South America and Africa fit together?(Evidence #1) S. America’s east coast fits like
a puzzle piece withAfrica’s west coast
How do South America and Africa fit together?
Evidence #1South America’s east coast fits like a puzzle piece withAfrica’s west coast.
Look at the two images.What do you noticeabout the mountainsin North America and Europe?
Look at the bottom picture.What do you noticeabout the mountainsin North America and Europe?The Appalachian Mtns. (USA) and the mountains in Europe once formed a single mountain range.(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
Evidence #4
Africa, South America, and Australia all have similar fossils
of the fern, Glossopteris.(lighter colored area below)
How is the fossil evidence useful for proving Continental Drift? (discuss & write)
How do we know that continents are pushed apart?
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 many smaller ones
Smithsonian
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 SequenceA. 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.
ContinentsNorth America Eurasia
South America Antarctica
Africa India
Australia
resources
• http://www.plainedgeschools.org/swells/plate_tectonics.htm
• http://slohs.slcusd.org/pages/teachers/rhamley/Biology/Continental%20Drift/Tectonics.html
• http://geology.rutgers.edu/103web/Pangeabreakup/breakupframe.html
What is continental drift?
1912 Alfred Wegener
Evidence shows that-• the continents are
moving
= Continental drift
• all continents once formed a supercontinent
= Pangaea
