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Chapter 2
H. Thiele
Earth Science
The Earth
Circumference: 40,007km at poles, 40,074 at
equator
Rotates on its axis at a 23.5° angle
71% water on the surface
91% of water is oceans
3% of water is fresh
Atmosphere
78% Nitrogen
21% Oxygen
1% Other
Discovering the Earth’s Interior
Determined through indirect
measurement
Seismic waves- vibrations that travel
through the earth from explosions or
earthquakes.
• P-waves: Travel fast, through solids, liquids,
and gases.
• S-waves: Travel slower, through solids only.
Zones of the Earth
Crust: thin, solid, outermost layer
1% of earth’s mass
Oceanic crust: more dense, 5km to 10km thick
Continental crust: less dense, 32km to 70km
Mantle: middle layer
66% of earth’s mass
2 parts
• Lithosphere-solid layer, 65km to 100km thick
• Asthenosphere- “plastic” layer 200km thick
Core: innermost dense liquid layer
Center of the earth composed mostly of iron
33% of earth’s mass
Other Weird Earth Stuff
The earth is a magnet:
It acts like a bar magnet with magnetic north near
the north pole
Causes the aurora
The earth has a strong gravitational force
As the distance from the center of the earth
increases weight decreases
The position of the north pole changes
Precession- axis moves in a circle over 26,000yrs
Movement of the Earth
Revolution: Earth goes around the sun
1 year
365.24 days
• Perihelion- closest to the sun
• Aphelion- farthest away from the sun
Rotation: Earth spins on its axis
1 day
24 hours
The Seasons
Summer:begins with
Summer Solstice
Fall: begins with Autumnal
Equinox
June 21 or 22
Sun’s rays 90° at Tropic of
Cancer
16 hrs of daylight
September 22 or 23
Sun’s rays 90° at Equator
12 hrs of daylight
Winter: begins with Winter
Solstice
Spring: begins with Vernal
Equinox
December 21 or 22
Sun’s rays 90° at Tropic of
Capricorn
8 hrs of daylight
March 21 or 22
Sun’s rays 90° at Equator
12 hrs of daylight
Time Zones
Standard time zones
24 zones 1 hr apart
15° apart (360/24)
International Date
Line
Where one day
changes to the next
Over pacific oceans
Daylight savings
time
Move clocks ahead in
spring
Move clocks back in
fall
Conserves energy
Artificial Satellites
Satellite: any object
in orbit of another
object with larger
mass
Geosynchronous
orbit: remains in the
same place around
the equator
Polar orbit: Remains
in the same line
north to south.
Orbits
Perigee: point closest
of earth
Apogee: point
farthest away from
the earth
THE END