THE DYNAMIC CRUST

Aim and Learning Target: Aim: How can we evaluate the structure and movement of the earth and identify its past movements? Learning Target: I can demonstrate that the earth has moved in the past and continuing to move using specific evidence from its structure.

Do Now:

The Dynamic Crust I. HOW do we know that movement of rocks takes place on Earth? A. Deformed Rock Structure - Sedimentary strata normally form in a horizontal position. Any change from the horizontal position is evidence of minor crustal change

Folded Strata

Tilted Strata

Faulted Strata

Fossil Evidence 1. Marine fossils found at high elevations suggest uplift.

Subsidence/sinking 2. Shallow water marine fossil found at great ocean depths suggest subsidence/sinking.

Plate Tectonics 1.Crust 5 – 35 km thick Density 2.7 – 3.0 g/cc 2.Mantle 2,900 km thick Density 3.3 – 5.5 g/cc 3.Outer Core 2,250 km thick Density 9.9 – 12.1 g/cc 4.Inner Core 1,220 km thick Density 12.7 – 13.0 g/cc

The crust contains both oceanic crust which is covered by our oceans and continental crust, that is the land on which we live.

Earth’s Surface 5 4. Upper Mantle Ocean 6. Lithosphere 3. Oceanic Crust

Lithosphere = Crust + Upper Mantle Asthenosphere – the plastic-like layer below the lithosphere in Earth’s Mantle

Theory of Continental Drift a. Alfred Wegner – proposed the theory of Continental Drift in the early 1900’s. b. He proposed that approximately 200 mya, all the continents existed as one large land mass which he called Pangaea.

Evidence for Continental Drift 1. Coastline of the continents – for example, the east coast of South America fits well with the west coast of Africa – like the pieces of a giant jig- saw puzzle.

Fossil Clues certain fossils of ancient life forms are found on widely separated continents. Mesosaurus was a small freshwater reptile. It’s fossils are found in Africa and South America

Rock Clues a. The Appalachian Mountains of the eastern US are geologically similar to the mountains in Greenland and western Europe, which include the Caledonian Mountains of Scotland. b. Structure, age, and mineral content of rocks are similar on the coasts of eastern South America and western Africa.

Climate Clues a. Coal, which forms from plants that grow in warm swampy environments, is found today in the colder climates of North America and Antarctica.