Transcript chapter 2
Chapter 2
Statistics
◦ Oblate spheroid – a
slightly flattened sphere
◦ Spins on its axis which
causes the polar regions
to flatten and equatorial
zone to bulge
Axis: imaginary straight
line running through the
Earth from North to
South Pole
Hydrosphere
◦ All the Earth’s water
◦ 71% covered by water
97% in the salty oceans
3% fresh water found in
lakes, rivers, and
streams, glaciers and
polar ice sheets
Atmosphere
◦ Blanket of gases that
surround the Earth
78% Nitrogen
21% Oxygen
1% other gases (argon,
carbon dioxide, & helium
Discoveries about
earth’s interior made
through seismic waves
◦ Vibrations that travel
through the earth
Zones
◦ Crust
Outermost Zone
◦ Mantle
Below the Crust
◦ Core
Below the Mantel
1% of the earth’s
mass
◦ Mass: the amount of
matter in an object
Oceanic Crust
◦ 5 km to 10 km thick
Continental Crust
◦ 15 km to 80 km
◦ Thickest beneath
high mountain
ranges
Zone of Rock nearly
2,900 km thick
2/3 of earth’s mass
Regions
◦ Lithosphere – uppermost;
cool and brittle
◦ Asthenosphere – just
below the lithosphere;
solid rock that flows
(plasticity)
Center of the earth
Mostly Iron
◦ Outer Core – Dense
liquid layer
◦ Inner Core – Dense
solid sphere
1/3 of earth’s mass
P Waves
◦ Primary waves
◦ Travel through liquids,
solids, and gases
◦ Travel faster than S waves
S Waves
◦ Secondary waves
◦ Travel through solids only
Speed and Direction
effected by composition
Both travel faster through
more-rigid materials
Seismic waves
Change in the speed of the
waves marks the boundary
between the crust and the
mantle
Increase in speed at the Moho
indicates the earth’s mantle is
denser than its crust
Below Moho a decrease in
seismic-wave speed marks the
boundary between lithosphere
and asthenosphere
Then increase in speed, then
slow, then disappear
Overall??
Locations on the earth’s
surface where neither S
waves nor P waves are
detected or where only P
waves are detected
Occur because the materials
that make up the earth’s
interior are not uniform in
rigidity
Differing rigidities – waves
bend and change direction
Two magnetic poles
Northern Geomagnetic
and Southern
Geomagnetic Poles
Magnetosphere: region
of space, effected by
earth’s magnetic field
Theorize - Liquid iron
in the outer core
Sun and the Moon have
magnetic fields, but
little iron
Weight: measure of the force of
the pull of gravity on an object.
Isaac Newton
Gravity – the force of
attraction that exists
between all matter in the
universe
Law of Gravity – the force of
attraction between any two
objects depends upon their
masses and the distance
between them
Mass does not change, but
weight does with location.
Force of gravity decreases
as distance from core
increases
Mass: amount of matter
in an object.
Revolution – movement of
the earth around the sun
◦ 365.24 days
Rotation – the earth
spinning on its axis
◦ 24 hours/1 day
◦ West to East
◦ Sun rises in the East; Sets in
the West
◦ Nighttime in the Western
hemisphere = Daytime in the
Eastern hemisphere
Orbit (path around the
sun) slightly elliptical
Closest point to the
sun – Perihelion
◦ January 3rd
Farthest point from the
sun – Aphelion
◦ July 4th
Earth’s axis tilted 23.5˚
As earth revolves axis
point does NOT change –
points to North Star
North pole tilts toward
sun
◦ Northern hemisphere
Longer periods of daylight
Sun’s rays strike at higher
angles
◦ Southern hemisphere
Shorter periods of daylight
Sun’s rays strike at lower
angles
South pole tilts toward
sun…what happens.
Changes in the angles at
which the sun’s rays
strike the earth’s surface
& changes in daylight
hours cause seasons
North pole tilted away =
less daylight hours
◦ Why? Sun’s rays on N.H.
are lower
◦ Season = Winter
◦ What would it be like in the
Southern Hemisphere?
Winter
Summer
Fall
Spring
Summer Solstice
◦ June 21 or 22
◦ North Pole tilts toward
sun
◦ Sun’s rays strike the
earth at 90˚ angle
along the Tropic of
Cancer
◦ Most hours of daylight
◦ Farther north of
equator = more
daylight hours.
◦ North of Arctic Circle =
24 hours of daylight
◦ Southern Hemisphere?
December 21 or 22
North Pole tilts away from
sun
Sun’s rays strike the earth at
90˚ angle along the Tropic of
Capricorn
Fewest hours of daylight
hours
Winter in the Northern
Hemisphere
Farther north less daylight
hours
North of Arctic Circle 24
hours of darkness
Southern Hemisphere?
• Equinox – “equal night”
• Daylight/darkness are equal
everywhere on earth
• North pole neither tilts toward
nor away
• Sun’s rays strike the earth at
90˚ angle along the equator.
Autumnal
◦ September 22 or 23
◦ Fall season in the
Northern Hemisphere
Vernal
◦ March 21 or 22
◦ Spring season in the
Northern Hemisphere
North Star or Polaris –
axis points toward!
Precession – caused by
forces acting on a
spinning body
◦ Causes the earth’s axis to
move slowly in a circle
◦ Complete one full circle
every 26,000 years
◦ Polaris continues for
many years
Sun is the basis for
measuring time
12:00 noon sun is
highest in the sky
Sun movement from
east to west
◦ Sun appears highest
over different locations
at different times
◦ Standard Time Zones
Noon is set as the time
when the sun is highest
over the center of that
zone
Earth’s circumference equals
360˚/24 hours which means
earth rotates at a rate of 15˚
each hour.
24 hour time zones cover
15˚
Time in each zone is one
hour earlier than the time
zone to its east
International Date Line
Daylight Saving Time
◦ Longitude line through the
Pacific Ocean
◦ Date changes from one day to
the next
◦ U.S. set 1 hour ahead for more
daylight hours
◦ Spring time
◦ Ends in Fall, return to Standard
time
◦ Spring forward; Fall back!!
Satellite – any object
in orbit around
another body with a
larger mass
◦ Put into orbit by
powerful computerguided rockets
◦ Earth’s gravity holds
the satellite in orbit
◦ The higher the orbit of
a satellite, the lower
the speed needed for it
to stay in orbit.
Geosynchronous Orbit
◦ Directly above the earth’s
equator and moving in
the direction of the
earth’s rotation
◦ Always remains at the
same point above the
equator and appears
stationary
◦ Useful for communication
Carries satellite over
the earth’s North and
South poles
Satellite passes over
a different portion of
the earth’s surface
during each
revolution
Mapping the earth’s
surface
American Scientific
Satellites
◦ Landsat
Polar orbit
Images of earth’s surface,
cities, vegetation regions,
and/or rock types etc…
◦ GPS
Global Positioning System
Network of satellites used
for accurate navigation of
ships and aircraft