I-6 Dynamic Planet Notes Activity Notes and Digging Deeper Notes
Key Question • Have the continents and oceans always been in the position they are today?
Evidence of a Super Continent • Continents fit together. See the match between the east coast of South America and the west coast of Africa. • Several of the world’s mountain ranges that appear on a continent today are similar in age and form to mountain ranges that are on another continent.
Several fossils are found on particular landmasses but not on others • Cynognathus was a reptile that lived in what are now Brazil and Africa • Lystrosaurus was found in central Africa, India, and Antarctica • Glossopteris was a fern found in Antarctica, Australia, India, Southern Africa, and South America
Mesosaurus was found in the southern tip of South America and the southern tip of Africa
Evidence produced by glaciers from long ago provide geoscientists with ideas about the movement of continents. • Like a bulldozer, a glacier plows a large pile of rock and sediment. When the glacier melts, the “plowed” deposit, called a terminal moraine, is left at the front of the glacier
Evidence of ice sheets 300 million years old has been found in the southern hemisphere
Continental Drift • Believed over 100 years ago based on observation of how Africa and South America fit together-Perhaps was once a single continent • Idea is that the single continent broke apart and the pieces drifted away from each other to form the Atlantic Ocean
Theory not accepted by geoscientists until the 1960’s • The Theory of Plate Tectonics gave a natural explanation for continental drift
Supercontinents • Geoscientists are sure that about 250 million years ago all of the Earth’s continents were gathered into a single “supercontinent” • Formed by a series of continent-continent collisions • Named Pangea (“Pan” means “all”, and “gea” means “land”)
Suture Zones • Evidence for the existence of Pangea • Former continent-continent collisions • Are found in the interiors of continents • Believed to be where earlier continents joined to form Pangea • Example, the Appalachian Mountains in North America
The Breakup of Pangea • About 200 million years ago the pattern of convection cells in the mantle changed • Caused Pangea to slowly split apart • Process is called continental rifting • Caused the Atlantic, Indian, and Antarctic Oceans to grow larger • Rifts didn’t develop in the same places where Pangea was first sutured together
There is evidence of earlier supercontinents. One may have existed about 600 million years ago. • At the time of Pangea, the Pacific Ocean was the only ocean! (Pacific Ocean is surrounded by subduction zones and is being consumed
Prediction for the Future • Pacific ocean will continue to shrink until all of today’s continents collect to form a new supercontinent • OR The pacific ocean will expand again, and the new oceans will close up again to form a Supercontinent where Pangea once existed (Scientists believe the latter)
The measurement of plate movement is made by using a satellite-based global positioning system (GPS)
I-6 AYR Questions • In your own words, explain the theory of continental drift. • What was Pangea? • How is a suture zone formed? • Why is the Pacific Ocean shrinking?