1. Layers of the Earth & Ocean Basins Origin & Structure Ch.2 The Sea Floor

4. I. Layers of the Earth

7. A. Crust 1.This is the layer that we live on 2.The thickness ranges from five miles under the oceanic crust (made of basalt) to 25 miles under the continental crust (made of granite) 3.Thinnest layer of the earth

8. I. Layers of the Earth B. Mantle 1.This layer is semi- liquid 2.Consists of magnesium, iron, & silicon 3.It is ~3000 km wide. 4.More solid closer to the Earth’s surface

11. I. Layers of the Earth C. Outer Core 1.Consists of liquid due to the high temperatures 2.It is 2100 km wide 3.This layer consists of nickel & iron

12. I. Layers of the Earth D. Inner Core 1.This layer is solid. a.Solid is due to the high pressure exerted on it from the outside layers 2. Consists of the metals nickel & iron 3. Its temperature is 6,000 o C 4. Its width is 2,100 km

18. II. Origin & Structure of Ocean Basins A. Continental Drift 1. First noticed in 1620 by Sir Francis Bacon 2. In 1912 Alfred Wegner proposed all the continents were joined into one supercontinent called “Pangaea” a. Not widely accepted because no mechanism is proposed

20. II. Origin & Structure of Ocean Basins B. Plate Tectonics 1. Continents drift as part of a process that involves the entire Earth’s surface

22. II. Origin & Structure of Ocean Basins B. Plate Tectonics 2. Mid-ocean ridge system, a continuous system of submarine volcanoes that encircles the world. 3.Deep depressions in the sea floor, called trenches

26. II. Origin & Structure of Ocean Basins C. Mid-Ocean Ridge Significance 1.Glomar Challenger, in 1968, began to collect sea floor core samples 2.Sea floor is very young near mid-ocean ridge crest, & it gets older the further away you get

27. II. Origin & Structure of Ocean Basins

29. C. Mid-Ocean Ridge Significance 3.Earth’s magnetic field has reversed in the past (magnetic anomalies)

34. II. Origin & Structure of Ocean Basins D. Creation of Sea Floor 1.Huge pieces of crust that separate at the mid- ocean ridge, creating cracks called rifts 2.Hot mantle pushes up through the rifts, cools, solidifies, and form new sea floor 3.Called sea floor spreading & explains the magnetic anomalies