The DynamicEarth

Earth Facts:• circumference around the poles is 40,007 km• circumference around the equator is

40,074 km• Earth is NOT a perfect sphere… it is a oblate

spheroid, a slightly flattened sphere

• Earth’s mass is approximately 6.0 x 1024 kg

• Earth’s average diameter is 12,735 km• Difference between the height of the tallest

mountains and the depth of the deepest ocean trenches is only 20 km

Layers above the Earth• Hydrosphere: all of the water that covers the Earth

• Atmosphere: blanket of gases that surround the Earth; 78% Nitrogen; 21% Oxygen; The rest (1%) is combination of argon, carbon dioxide

helium and water

• Atmosphere is divided up into 5 regions

Layers inside the Earth

Layers inside the EarthCrust: The thin, solid outermost zone

of the Earth

• Makes up only 1% of Earth’s mass

• Oceanic Crust: crust under the oceans• Only 5km to 10km thick

• Continental Crust: crust that makes up thecontinents

• 15km to 80km thick• Thickest beneath high mountain ranges

Layers inside the EarthMantle: Zone of rock nearly 2,900km thick

Makes up almost 67% of Earth’s massLayers of the Mantle:

Lithosphere: uppermost part of the mantle and the crust above it; cool and brittle. The boundary between the crust and mantle is referred to as the MOHO

Asthenosphere: solid rock with the ability to flow due to heat and pressure (plasticity)

Mesosphere: increasingly dense and solid rock layer (aka “Lower Mantle”)

Layers inside the EarthCore: Center of the earth made up mostly

of iron

Outer core: dense liquid layer about 2,250km thick

Inner core: dense solid layer about 1,228km thick

Together the inner and outer core make up about 33.3 % of Earth’s mass

P and S Waves

Liquids and Solids

How Do We Know?

Seismic Wave Studies

We will talk more about seismic waves when we study Earthquakes!

The Earth As A Magnet

The Earth’s Gravity

Sir Isaac Newton’s Law of Gravitation: The force of attraction between two objects depends on the mass of the objects and the distance between them.

Weight: A measure of the strength of the pull of gravity on an object

Weight and Mass are NOT the same….

EUREKA !

The Earth is not perfectly round it is slightly wider around the Equator

So… a person standing at the Equator is farther from the center of the Earth than a person standing at the North Pole.

The person at the Equator will weigh less because he is farther from the center of the Earth.

The Movements of the Earth

How fast is the Earth spinning?

0.5 km/sec Called: ROTATION

Time it takes for Earth to ROTATE once on it’s axis: 24 hours

How fast is the Earth revolving around the Sun?

30 km/sec Called: REVOLUTION

Time it takes for Earth to REVOLVE once around the sun: 365.24 days (1 year)

How far is the Earth from the sun when it is CLOSEST TO IT?

147,100,000km Called:Perihelion

How far is the Earth from the sun when it is FARTHEST FROM IT?

152,600,000km Called:Aphelion

The Earth is tilted on it’s axis

The Reasons for the Seasons