1-1 Drifting Continents
What is Pangaea?
Pangaea was the supercontinent that joined all of the continents together 300 million years ago
What are mid-ocean ridges?
Mid-ocean ridges are a long chain of mountains that rise up the ocean floor.
At which boundary do two plates pull apart?
Plates pull apart from each other at divergent boundaries.
What force causes the movement of Earth's plates?
Convection currents
What did Wegener think happens during continental drift?
Wegener thought that the continents move slowly
Where does the ocean floor sink back down into the mantle?
The ocean floor sinks back down into the mantle at deep-ocean trenches.
When a divergent boundary occurs on land, it forms a ______
When a divergent boundary occurs on land, it forms a rift valley
What is subduction?
Subduction is the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle again.
What two pieces of Evidence did Wegener use to support his hypothesis of continental drift?
1. The continents fit together like a puzzle
2. There are fossils of the same plants and animals across many different continents.
Why did the discovery of sea-floor spreading support the hypothesis of continental drift?
The discovery of sea-floor spreading supported the hypothesis of continental drift because it proved that there is a mechanism that can move continents.
What is a transform boundary?
Transform boundaries are where two plates slip past each other in opposite directions.
Which of the following is evidence for sea-floor spreading?
A. Matching patterns of magnetic stripes found in the crust of the ocean floor.
B. new rock found farther from mid-ocean ridges than older rock
C. pieces of different crust found on different continents
D. Changes in climate on the continent of Africa
A. Matching patterns of magnetic stripes found in the crust of the ocean floor.
Wegener's hypothesis was that all the continents were once ____
Wegener's hypothesis was that all the continents were once joined together in a single landmass and have since split apart.
Sea-floor spreading adds _____________. At the same time, older strips of rock _________.
Sea-floor spreading adds more crust to the ocean floor. At the same time, older strips of rock move outward from either side of the ridge.
At which boundary do two plates run into each other? What landforms are made from this kind of boundary?
When two plates run into each other it is a convergent boundary. Convergent boundaries make mountains and sometimes volcanoes.
What is the theory of plate tectonics?
The theory of plate tectonics states that Earth's plates are in slow, constant motion, driven by convection currents in the mantle.
How do fossils give evidence that supports continental drift?
Fossils of the same ancient tropical plants and animals have been found on South America, Africa, Australia, India, and Antarctica. Wegener inferred that these organisms once lived on a single landmass (Pangaea) that has since split apart.
Why are the oldest parts of the ocean floor no older than about 200 million years?
Because very old parts of the ocean undergo subduction at deep ocean trenches.
It takes 100,000 years for a plate to move about 2 kilometers. How fast is the plate moving?
The plate is moving at 2 cm per year
Wegener proposed that mountains form when continents collide, crumpling up their edges. Was Wegener's idea consistent with his hypothesis of continental drift? Explain.
Yes, it was consistent because if the continents can drift then they can collide with each other to form mountains.