Introduction to Planet Earth

Let’s dig a hole to China!

Earth Stats

• The Earth's mass is about 5.98 x 1024 kg.

• Earth is the densest planet in our Solar System (mass/volume).

• Earth is made of several layers with different compositions and physical properties, like temperature, density, and the ability to flow.

The Composition of the Earth

The Composition of the Earth

Crust• Thinnest layer (5-100 km)• Two types of crust

• Continental • Like granite• Average 30 km

• Oceanic• Like basalt

(Basalt is denser than granite!)• Average 5-8 km

The Composition of the Earth

Mantle• Extremely Thick! (2,900 km)• It is too far down to drill

• How do we know what it is made of?

• Scientists infer based on:• Pushed up rock• Ocean floor/molten rock

• What is it like?• Like the mineral olivine

• Large amounts of iron and magnesium

www.soc.soton.ac.uk

The Composition of the Earth

Core• Pretty darn big. (6,856 km)

• (Slightly bigger than Mars!)• 33% mass of the Earth

• Scientists think….• Made mostly of iron• Some nickel, sulfur, oxygen

• What is the evidence?• The particular way seismic

waves travel• Earth’s Magnetic field

N

S

The Structure

of the Earth

Inner CoreSolid

Outer CoreLiquid

MesosphereSolid

AsthenosphereViscous Liquid

LithosphereSolid

Asthenosphere = ‘weak sphere’Lower part of Mantle

Lithosphere = ‘rock sphere’Crust and upper rigid part of Mantle

How HOT is it?

Surface of Sun! 5,500°CSun Core 15,000,000°C

Convection• Convection (heat) currents

– carry heat from the hot inner mantle to the cooler outer mantle.

• The mantle gets warmer with depth • top of the mantle is ~ 1,600° F (870° C)• bottom of the mantle is ~4,000-6,700° F

(2,200-3,700° C) • The mantle contains most of the mass of

the Earth

Let’s Make Models of the Earth!

• Inner Core (yellow) diameter 2 cm (4)• Outer core (orange) diameter 6 cm (4)• Mesosphere (red) diameter 11cm (4)• Asthenosphere (brown) diameter 12cm (2)• Lithosphere (sand)

– -after assembly roll edges of asthenosphere in glue and then sand (1.5mM thick)