Welcome to Geology at Miramar

1. Welcome to Geology at Miramar

2. Chapter 1- Introduction

3. The Nebular Hypothesis • The solar system began as dust and gas (from an exploding supernova?) collapsed due to gravity. • The nebula contracted into a rotating disk. • Repeated collisions of rocky and metallic material coalesced into asteroid, then planet-sized bodies. • Age of the earth and solar system about 4.5 billion years (4500 million years). • Heating and subsequent cooling of Earth caused heavy metals to sink to the interior and lighter elements to rise to the surface.

4. Earth’s internal structure • Earth’s internal layers can be defined by • Chemical composition • Physical properties(molten, solid) • Layers defined by composition • Crust: silica (SiO2)-rich composition • Mantle: silica and iron composition • Core: iron and nickel composition

5. Earth’s internal structure Figure 1.13

6. Earth’s layers by physical properties In the crust and upper mantle: • Lithosphere – rigid solid which make up the tectonic plates, includes both crust and mantle • Asthenosphere – partially molten “weak” layer • Lower mantle (mesosphere) mostly solid Core • outer core (molten • inner core (solid)

7. Earth’s internal structure Figure 1.13

8. Continental and Ocean Crust • Continental crust is thicker (average 35-40 km) older (up to 4 billion years old) and is generally less dense than ocean crust. • Ocean crust averages 5-7 km thick, is 200 million years old or younger and is mostly composed of dark volcanic rock basalt.

9. Age of the Ocean Floor

10. Plate Tectonics: the new paradigm From left to right: • Transform boundary (conservative) • Convergent boundary (destructive) • Divergent boundary (constructive)