Download Unit One: Earth Dimensions Although the Earth appears to be a

Unit One: Earth Dimensions
Although the Earth appears to be a perfect sphere, by actual measurement, the Earth
is an OBLATE SPHEROID, having a larger circumference around the equator than
the poles.
Circumferences of the Earth:
At Equator- 40,076 kilometers
At Poles- 40,008 kilometers
Equatorial Diameter- 12,757 kilometers
Polar Diameter- 12,714 kilometers
***Remember the Earth is slightly bulged at the equator and slightly flattened at the
poles.
Evidences of Earth’s Shape
1. Polaris, the North Star can be used to help determine the Earth’s shape
According to the principle of the geometry of a sphere, the altitude of
Polaris is equal to the latitude of the observer.
Apparent counterclockwise motion of stars around the North Star
Altitude- a celestial objects’ angular distance above the horizon
Latitude- distance north or south of the equator measured in degrees 0o at the equator
and 90o at the poles
2. Photographs of the Earth from Space
3. Law of Gravitation
Gravity- the force of attraction between two objects
Same objects weigh more at the poles than at the equator of the Earth because
there is a greater gravitational pull at the poles than at the equator.
4. Sinking Ship Theory
Earth’s “SPHERES”
ATMOSPHERE
Composed of materials that form a thin envelope surrounding the Earth held in
place by gravitation
The atmosphere is stratified into zones each having different temperature, pressure
ranges, composition, and effects on Earth. They are the following:
Mesosphere- 30 to 90 kilometers
above Earth’s surface with a
decreasing temperature from 100 C
to -900C as altitude increases
Stratosphere
Above the troposphere and below
the mesosphere with an increasing
temperature as altitude increases
due to the presence of ozone
Troposphere
Lowest region of the atmosphere
with a decreasing temperatures
altitude increases
Thermosphere- Outermost shell of
atmosphere where temperature
continuously increases as altitude
increases
***The atmosphere is the least dense of the Earth’s spheres (lithosphere, atmosphere,
and hydrosphere)
HYDROSPHERE
Almost three quarters (71%) is covered with water
Sphere is relatively thin as it is only 3.5 to 4.0 kilometers thick
Hydrosphere includes salt-water (oceans) as well as freshwaters (lakes and rivers)
LITHOSPHERE
The most solid portion of the Earth is the rock near the Earth’s surface which
includes mountains, valleys, and the ocean floor.
 The parallels of latitude is the equator that is located halfway between the North and
South Poles
 Prime Meridian has a longitude of 00 and runs through Greenwich, England.
LATITUDE- distance measured in degrees north or south of the equator (LINES RUN
EAST AND WEST)
LONGITUDE- lines RUN NORTH AND SOUTH but is measured in degrees east and
west of the Prime Meridian
***How do we name the coordinates of a place using longitude and latitude???
We say latitude first, then longitude.