Plate Tectonics Lecture Chapter 2
- 1. Plate Tectonics Mr. McKay Earth Science
- 2. Drifting Continents Evidence of drifting Fossils found on both of the continents of Africa and South America that are of the same organism Fossils: The preserved remains of ancient organisms German scientist Alfred Wegner came up with the theory of continental drift , he was actually a meteorologist and not a geologist The theory called the giant landmass that once was on Earth Pangaea Pangaea : Means all Earth Early Earth & Plate Tectonics
- 3. Fossil Evidence Fossils play a key role in supporting the theory of Continental drift Glossopteris is an extinct plant They are found in rocks that are around 250,000,000 years old ( 250 million) The seeds were to large to be carried by wind and too fragile to have survived ocean waves The fact that they are found in Antarctica implies that they had to be in a better climate than what is present Antarctica
- 4. Fossils Glossopteris: a fern found on the southern continents Cynognathus: a land reptile found in South America and Africa Lystrosaurus: a land reptile found in Africa, Antarctica, and India Mesosaurus: a freshwater swimming reptile found in Africa and South America
- 5. Fossil Evidence From Rocks Not only fossils provide evidence for theory support Rocks in Africa and South America When you examine the continents from these two they look as if they could piece together like a puzzle The layers of coal depth line up with each other Rock deposits from glaciers also match
- 6. Divergent Boundary Divergent Boundaries Constructive-add new land Mid-ocean Ridge Ocean floor moves away on either side of the ridge Called sea-floor spreading Often offset by transform faults which causes a curve in the ridge Transform Faults Sea-Floor Spreading/Mid-Ocean Ridge Spreading Sea Floor Basic Plate Boundaries
- 7. Magnetic Rock Strips Some minerals have magnetic properties These minerals line up with the Earth’s magnetic poles When the molten rock hardens, a permanent record of the Earth’s magnetism remains The Earth’s magnetic poles have reversed themselves from time to time Animation Sea Floor Spreading
- 8. Convergent Boundaries Plates collide-destructive Two continents colliding build mountains or plateaus The Indian Plate and the Eurasian Plate collide to form the Himalayas which have Mt. Everest , the highest mountain on Earth.
- 9. Convergent Boundary Destructive-crust is destroyed (melted by the mantle) Called Subduction When oceanic and continental crust collide Oceanic crust is pushed down into the mantle and melted Some of this melted material surges upward
- 10. The continental crust is also forced upward producing volcanoes The Cascade Range in Washington and Oregon are an example of this Convergent Boundaries Convergent Boundaries
- 11. Convergent Boundaries When two oceanic plates collide subduction occurs The older denser plate is pushed into the mantle and melted Some of the material rises upward and erupts on the ocean floor forming an island arc
- 12. Theory of Plate Tectonics Tectonics: refers to the branch of geology that is concerned with plate movements Theory of Plate Tectonics: Links together the ideas of continental drift and ocean floor spreading to explain how the Earth has evolved over time. It explains the formation, movements, collisions, and destruction of the Earth’s crust According to the theory the Earth’s uppermost layer, called the lithosphere, is made up of plates
- 13. Lithospheric Plates There are seven major plates The Pacific Plate- which covers 1/5 of the Earth North American South American Eurasian African Indo-Australian Antarctic Plates There are also Many smaller plates Caribbean Arabian Plate Tectonics Review