Section 1 – Earth: A Unique Planet
Earth Basics
Third planet from the sun in our solar system
4.6 billions years old
71% of the surface is covered by water
Global ocean – relatively thin layer of water that covers earth’s
surface
shape of earth is an oblate spheroid – slightly flattened sphere
polar regions flatten and the equator is bulged (why?)
surface is relatively smooth
Earth’s Interior
Discoveries made by seismic waves – vibrations that travel through earth
Compositional Zones
1. crust – thin, solid outermost zone of Earth
a. oceanic crust – crust beneath oceans
b. continental crust – crust that makes up the continents
2. mantle – the layer that underlies the crust
a. denser than the crust
b. nearly 2900 km thick
c. 2/3 of earth’s mass
3. core – central part of the Earth below the mantle
a. iron
b. nickel
Structural Zones
1. lithosphere – the solid, outer layer of Earth that consist of the
crust and the rigid upper part of the mantle
2. asthenosphere – the solid, plastic layer of the mantle beneath the
lithosphere; made of mantle rock that flows very slowly, which
allows tectonic plates to move on top of it
3. mesosphere – the “middle sphere”; the strong lower part of the
mantle between the asthenosphere and the outer core
4. outer core – a dense liquid at a depth of 2900 km
5. inner core – a dense, rigid solid at a depth of 5900 km
Earth as a Magnet
Two magnetic poles
Extends beyond the atmosphere and affects a region of space called
the magnetosphere
- source may be the liquid iron core
- may be produced by motions within the core that produces
electric currents that in turn create Earth’s magnetic field
- Sun and Moon also have magnetic fields
Earth’s Gravity
Gravity – the force of attraction that exists between all matter in
the universe
Law of Gravitation – the force of attraction between any two objects
depends on the masses of the objects and distance between
the two objects
Weight and Mass
Weight – a measure of the strength of the pull of gravity on
an object. The Newton (N) is the SI unit used to measure
weight.
The mass of an object does not change regardless of location,
but the weight of the object will change. Why?
Weight and Location
Weight varies according to the location on Earth’s surface.
Weight at the equator would be about 0.3% less than the
weight at the poles. Why?