Earth is NOT a perfect sphere… it is a oblate spheroid, a slightly flattened sphere
Earth’s mass is approximately 6.0 x 10 24 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 Earth Crust: 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 the continents
15km to 80km thick
Thickest beneath high mountain ranges
Layers inside the Earth Mantle: Zone of rock nearly 2,900km thick Makes up almost 67% of Earth’s mass Layers 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 Earth Core: 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