1. Clues in the Crust

2. Need To Know Background Information  The formation of Mountains is a slow movement of Earth’s Crust where earthquakes and volcanoes are much more rapid and violent.  Scientist can explain both types of movement by studying cross sections of the sea floor.

3.  A cross section is a drawing of what you see when you cut through an object.

5. Ocean Floor Morphology  Ocean Ridge – the raised floor, which can become large enough to be considered an underwater mountain range. ie Juan de Fuca Ridge  Continental Slope – a deep slope in the seabed between a continental shelf and the sea floor.  Continental Shelf – a shallow underwater ledge located between a continent and the deep ocean. Cross section

6.  Abyssal Plain – a large flat area on the sea floor. Abyssal plains make up a large part of the sea floor.  Rift – an opening in the oceanic crust, where molten materials from Earth’s mantle can escape. Cross section

7. How Does Earth’s Crust Move?  A scientist who searched for answers was a German Meteorologist (studies climate and weather), Alfred Wegener (1880- 1930). Wegener noticed that the continents almost fit together like a puzzle.

8. Pangaea  Wegener thought that the fit of the continents was more than just a coincidence. He suggested that all the continents were joined together in a huge land mass called Pangaea. He suggested that Pangaea broke apart about 200 million years ago.

10. Another Theory from Wegener  Wegener also proposed the theory of continental drift. According to the theory of continental drift, the continents change position very slowly, moving over the surface of Earth a few centimeters every year.  Most of the scientists of Wegener’s time strongly disagreed with him. Wegener could not explain how the continents moved but collected as much evidence as he could. He collected fossils and rocks.

11.  As Wegener looked more carefully at the climates suggested by the fossils and geology in different areas, he saw unexpected similarities between continents that are no longer close together. He and Vladimir Koppen marked all the climates on the continents and then tried to put the continents together based on their paleoclimatic evidence. They found the continents fit together like a puzzle. Wegener based his theory of continental drift on biological, geological and meteorological evidence.

12. Fossil Evidence  Fossils of the reptile Mesosaurus have been found in South America and Africa. Mesosaurus lived in fresh water and on land and probably could not swim between continents.Wegener hypothesized that this reptile lived on both continents when they were joined.

13. Evidence From Rocks  The Appalachian Mountains in eastern North America are made of the same kind of rock as a mountain range in Britain and Norway. There are similarities between rock in Quebec and rock in northern Britain. There are also similarities between rock in South America and rock in Africa.

14. Rock Evidence

15. Modern Day Evidence  Technological advances have allowed geologists to actually touch the sea floor sediments that were found over 1000m deep.  Scientists have used Sonar, Seismic Waves and Core Samples to confirm Wegener’s theory of continental drift.