1. Big Bang Theory: highly condensed form of energy exploded. - homogeneous universe: comes from one. 2. Inflation Theory: after Big Bang, the universe passed through a phase of exponential expansion driven by rapid cooling of particles which formed a pseudovacuum. 3. Earth was formed 4.6 billion years ago.

1. Falling of matter toward the center. Loses energy (E) and therefore gives off heat. (exothermic) 2. Particles bombard into each other and give off bombardment heat (E). 3. Radioactive particles give off E. Nickel and Iron melt from heat and move toward center due to their high densities

 Earth is made up of 4 main layers:  Inner core  Outer core  Mantle  Crust (where we live)

 Inner core: solid sphere approximately 1220 km in radius; believed to be primarily nickel- iron alloy. Temperature: 5,000-6,000 ˚C  Outer core: liquid, 2300 km thick. Composed of nickel-iron alloy

 The mantle is approximately 2,900 km thick and comprises 70% of Earth's volume. (the core makes up about 30% of Earth's volume, with the outer crust [where we live] <1%!!). ▪ The mantle is divided into sections based upon changes in its elastic properties with depth. ▪ In the mantle, temperatures range between degrees Celsius at the upper boundary with the crust to over 4,000 degrees Celsius at the boundary with the core. ▪ Due to the temperature difference between the Earth's surface and outer core, and the ability of the crystalline rocks at high pressure and temperature to undergo slow, creeping, viscous-like deformation over millions of years, there is a convective material circulation in the mantle (mantle convection cells). Hot material rises up as mantle plumes (like a lava lamp!), while cooler (and heavier) material sinks downward to be reheated and rise up again.  We’ll see that this process is very important for plate tectonic motion…

The outer most layer is the crust - this is the most familiar to us as it is where we live. Oceanic Crust: more dense, composed of basalt, diabase and gabbro. Continental Crust: less dense, composed of less dense rocks such as granite

 The outer 100 km or so  Composed of the crust and upper mantle  Broken into a number of small and large plates

 Plastic layer in the upper mantle  Lithosphere plates moves over the asthenosphere at a rate of a few cm per year.

 AKA: Moho  Lies between the crust and the mantle  Adheres the crust and the upper mantle together (lithosphere) so the plates can glide on the asthenosphere Image of Earth's internal structure by USGS - Mohorovicic Discontinuity (red line) added by Geology.com  So if plates glide on the asthenosphere…. where does that lead us?

Can you fit the continents together like puzzle pieces??

Did your map look like this??

 Alfred Wegener (1912)- suggested that continents were not always in their current positions b/c 1)the continents seemed to fit together like jigsaw puzzle 2) fossils were found on different continents that couldn’t cross the oceans 3) presence of glacial deposits on continents found near the equator 4) similarity of rock sequences on different continents  He called this Continental Drift

 plates move by underlying hot mantle convection cells

 Where plates slide past each other  earthquakes 1. Transform Boundaries Above: View of the San Andreas transform fault

 Forms mountains, ex: Alps, Himalayas  earthquakes Continent-Continent Collision 2. Convergent Boundaries (continent-continent)

 Called SUBDUCTION- oceanic slides under continental (volcanic mts & trench); ex. Andes  earthquakes Continent-Oceanic Crust Collision 2. Convergent Boundaries (continent-oceanic)

 1 plate runs over the other causing it to sink into the mantle forming a subduction zone. =a trench. Ex: Mariana Trench is 11 km deep! Deepest point on planet -earthquakes Ocean-Ocean Plate Collision 2. Convergent Boundaries (oceanic-oceanic)

Ex: Mid-ocean ridges  plates move apart, new material erupts to fill gap  A.K.A. sea-floor spreading 3. Divergent Boundaries

Ex: Iceland 3. Divergent Boundaries

 1960’s Harry Hess proposed the hypothesis of sea- floor spreading in which magma from the mantle rises to create new ocean floor at mid-ocean ridges.  Youngest rocks are closer to the ridge and the older rocks are further away.  Magnetic Banding: Magnetic minerals of the magma align themselves with the direction of the Earth’s magnetic field.

 Thought to arise from the movement of liquid in the outer core as the planet rotates  1960’s discovered that the Earth’s magnetic field periodically reverses.  As the magma rises to form new ocean floor at the mid-ocean ridge it records the polarity of the magnetic field.

 Hot mantle plumes breaching the surface in the middle of a tectonic plate  Hawaiian Islands What are Hotspot Volcanoes? Photo: Tom Pfeiffer / Hotspots (not at plate boundaries)

The tectonic plate moves over a fixed hotspot forming a chain of volcanoes. The volcanoes get younger from one end to the other.