1. The Structure of the Earth Understanding the structure of the Earth begins with an understanding of how the Earth came to be…

3. Composition of Earth Three Major Layers… 1. Crust 2. Mantle 3. Core *Layers are made of different kinds of materials Outermost layers: lightest materials Innermost layers: densest materials

4. The Crust Outermost layer; thinnest; layer we live on Two types: 1.Contintental – composition similar to granite; about 25 miles thick beneath continents; not as dense as oceanic crust 2.Oceanic – composition similar to basalt; about 6.5 miles thick beneath ocean; denser than granite Known as the lithosphere: “rock sphere” Made of tectonic plates

5. The Crust Layer we know the most about Made of mixture of elements 8 most common elements in Earth’s crust by mass: 46.6% Oxygen (O)3.6% Calcium (Ca) 27.7% Silica (Si)2.8% Sodium (Na) 8.1% Aluminum (Al)2.6% Potassium (K) 5.0% Iron (Fe)2.1% Magnesium (Mg)

6. Earth’s Layers

7. Diagram: Inside the Earth

8. The Mantle Layer between the crust and the core  Asthenosphere: upper mantle; layer of weakened rock between crust and mantle; means “weak sphere” Extremely thick; 2/3 of the Earth’s mass No one has ever seen this layer; observations made from surface (volcanoes/lava) Made of almost solid rock (magma), flows slowly like thick tar or fudge Also known as the mesosphere

9. The Core Two regions: outer and inner core Extremely hot; under great pressure Outer Core: liquid iron; generates a magnetic field Inner core: solid iron; some nickel; pressure so great it cannot melt, atoms vibrate in place, friction adds to temperature

10. Scientific Physical Layers Five physical layers –Lithosphere (Crust/Uppermost Mantle) –Asthenosphere (Upper Mantle) –Mesosphere (Mantle) –Outer core –Inner core

11. Review! Five main physical layers Lithosphere (uppermost mantle): “rock sphere”; tectonic plates Asthenosphere (upper mantle): “weak sphere”; soft layer, thick flowing molten rock; pieces of lithosphere move on this layer Mesosphere (mantle): “middle sphere”; magma: hotter, more fluid Outer core: liquid layer molten metals Inner core: solid metal

12. Continental Drift Theory (Plate Tectonics)

13. Tectonic Plates Pieces of the Earth’s crust move on top of the asthenosphere Each plate carries a continent, ocean basin or both Fit together like a jigsaw puzzle or cracked egg Drift apart to form rifts and valleys (sea-floor spreading) Collide to form mountain ranges Some cracks called faults slip under great pressure and cause release of energy as seismic waves (earthquakes)

14. Pangaea Supercontinent of volcanic land masses Split apart into pieces and moved to form the continents today as we know them Evidence includes same rocks found on South American and African coasts and fossils found on neighboring land masses