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 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)