1. Chapter 22 ISCI 2001 Structure of the Earth Tectonics

2. Crust (1). Thin, brittle Oceanic Basalt rock (dark); greater density Continental Granitic rock (lighter); less dense Less dense than mantle Floats

3. Mantle (1). Most of the volume (82%) and mass (65%) – Thickest layer (2). Rich in Si and O – Contains Fe, Mg, Ca (causes increased density) Density increased by weight of crust also (3). Hotter than crust – High pressure Caused by radio active decay of elements Flow of heat from core (4). Regions – Upper Mantle – Lithosphere Stiff, cool – similar to crust (forms one layer together) – Asthenosphere Solid, plastic (solid flow) (5). Upper Mantle – Solid and rigid – Plastic but not as much as upper mantle

4. Core Consist of: Metallic Fe 2x dense as mantle (2). Inner Core Solid 4000 to 7000 C Radioactive elements Earth development; matter hitting the surface Core sinking to the center (3). Outer Core Flows due to less pressure Rotation of Earth stirs up core material Produces magnetic field (flowing electrical charge)

5. Plate Tectonics (1). Continents sit atop of tectonic plates What are the plates made of? What is a continent? (2). Plates Consist of mantle and the crust (lithosphere) Plates move atop the asthenosphere (plastic) Continents move because they are embedded into the plates (3). Plate boundaries and continents Continents and plates do not have the same boundaries (overlapping) Figure 22.18 A lot of action occurs at the plate boundaries!

6. Plates

7. How were the Plates Discovered? (1). Alfred Wegener Proposed the theory of “Continental Drift” Continents are in motion; drifting over geologic time Pangea (figure 22.8) Same fossils found in several different continents Matching rocks on both sides of Atlantic Ocean (2). Evidence for CD Seafloor Spreading Magnetic Stripes

8. Pangea

9. Evidence for Continental Drift – Seafloor Spreading (1). Magma flows out of breaks in lithosphere New lithosphere is formed and old lithosphere will be recycled back in trenches (22.16) Mid-ocean ridge Pushes the continents in specific directions

10. Evidence – Magnetic Stripes (1). Lava contains Fe and magnetite (Fe and O) Crystals are magnetic – line up with the magnetic field of the Earth Crystals point North and south / cool and freeze and become locked in Contains a record of the history of the magnetic field of the Earth Gives a striped, bar pattern (22.17) Alternates normal (today’s field) and reversed field from years ago. Runs along the spreading seafloor

11. How do the Plates Move? (1). As magma is heated deep in the Earth it moves upward via convection currents (22.21) Hot rocks from lower mantle move upward cool in the upper mantle and return Hit the lithosphere and can crack it – seafloor spreading Plates move atop ‘convection cells’