EarthSci - Intro to Geology

Spatial Scales

Atom → Mineral → Rock
Mountain → Continent → Earth

Temporal Scale

Earth - 4.6 billion yrs
Atlantic Ocean to open - 150 million yrs
Rocky Mountains age - 60 million yrs
Humans evolve - 2 million yrs
Last big glaciation in Hamilton - 10K yrs
Eruption of Mt. St. Helen - 6 mins
Earthquakes - few seconds

Four layers of the Earth

1. Crust (solid)

2. Mantle (flowing solid & molten)

3. Outer Core (molten)

4. Inner Core (solid)

Layers of the Earth

Lithosphere - crust + uppermost mantle (solid)
Asthenosphere - lower mantle (flow)

Earth’s Composition

Contains heavier elements
By least to most:

1. Iron

2. Oxygen

3. Silicon

4. Magnesium

5. Nickel, sulfur, calcium, aluminum

Crust’s Composition

Contains light elements

1. Oxygen

2. Silicon

3. Aluminum

4. Iron

5. Magnesium, calcium, potassium, sodium

Continental crust - thicker, granitic rocks, rich in Si, Al, Na & K (light elements)

Oceanic crust - thinner & denser/heavier, basalt & gabbro rocks, rich in Fe & Mg

What causes thinning & thickening of the crust?

Thinning: crustal stretching
Thickening: mountain building

Mantle’s composition

Makes up most of the Earth’s volume & mass
Rich in Fe & Mg = Peridotite

Outer Core’s composition

Density changes due to it being molten

Mostly Fe & Si

How is the Earth’s magnetic field generated?

From the outer core. Convection of really hot electrically conductive liquid iron & nickel, driven by heat from the inner core & Earth’s rotation, creates electric currents that produce their own magnetic fields.

Inner Core’s composition

Solid, metallic core made of mainly Fe & Ni