Drift Happens
This scientist proposed the hypothesis of continental drift in 1912.
Alfred Wegener
These remains or traces of ancient organisms helped support continental drift.
Fossils.
These are long underwater mountain chains found throughout Earth’s oceans.
Mid-ocean ridges
This process happens when oceanic crust sinks back into the mantle.
Subduction.
Atlantic Ocean.
This supercontinent contained all of Earth’s continents millions of years ago.
Pangaea
Scientists found matching fossils on continents that are now separated by this major Earth feature.
Oceans.
Sea-floor spreading.
These deep underwater valleys form where subduction occurs.
Ocean trenches.
This ocean is shrinking because crust is recycled faster than it is created.
Pacific Ocean.
The coastlines of these two continents appear to fit together like puzzle pieces.
South America and Africa
Explain why finding the same fossils on different continents was surprising to scientists.
The continents are far apart today, so scientists wondered how the same organisms could appear on both.
The youngest ocean floor rocks are found in this location.
Near the mid-ocean ridge.
As oceanic crust moves away from a ridge, it becomes more dense and heavier. What eventually happens to it?
It subducts/sinks into the mantle.
Explain why scientists think the Pacific Ocean may eventually disappear.
Subduction zones around it recycle crust faster than new crust forms.
Scientists found coal deposits in places that are now too cold for tropical plants. Why does this support the hypothesis of continental drift?
It suggests that the continents were once in different climates or locations, and later moved.
Scientists discovered fossils of the same ancient plants in South America and Africa. What did this suggest?
The continents were once connected.
Explain why ocean floor rocks farther from the ridge are older.
New crust forms at the ridge and pushes older rock away over time.
Explain why oceanic crust subducts beneath continental crust.
Oceanic crust is denser and heavier.
Scientists predict this may happen between Africa and Europe millions of years from now.
They may collide.
An island in the Arctic contains fossils of tropical plants. What does this tell us about the movement of the continents?
The land was once closer to the equator and drifted north over time.
A student claims continents have always been where they are today. Use fossil evidence to explain why scientists disagree.
Scientists found the same fossils on continents separated by oceans, suggesting the continents were once joined together and later drifted apart.
Scientists discovered pillow rocks near ridges. Explain how pillow rocks support sea-floor spreading.
Pillow rocks form when lava cools underwater, showing volcanic activity where new crust forms.
Explain how subduction helps recycle Earth’s crust.
Oceanic crust sinks into the mantle at subduction zones, where it melts and becomes part of the mantle again.
A student says, “Earth’s crust never changes because continents look permanent.” Use TWO pieces of evidence to prove them wrong.
Answers may include fossils on different continents, matching mountain ranges, sea-floor spreading, mid-ocean ridges, subduction, climate evidence, etc.