Measuring the Earth

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Unit 2

• Measuring the Earth

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Size and Shape of Earth

• What is Earths shape?

• What is Earths shape?

C
A
B
Almost a perfect sphere

• Models are used to represent the properties of an
  object or system.
• Example The globe is a model for Earth.

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Earths Size and Shape

• Evidence
• The mast of a ship was the first to appear over
  the horizon and last to disappear.
• When ships sailed south, sailors observed that
  the North Star gradually and evenly got closer to
  the horizon.
• During an eclipse of the moon the Earth casts a
  spherical shadow on the moon.
• Scientists today have the advantage of
  photographs taken from the moon to prove the
  Earth is spherical.

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Spheres of the Earth

• Atmosphere
• - Layer of gases that surrounds the Earth
• - Composed mostly of nitrogen and oxygen
• - The atmosphere is layered into zones

• Hydrosphere
• - The layer of liquid water that lies between the
  atmosphere and much of the upper layer of the
  Earths interior

• Lithosphere
• - The layer of rock that forms the outer shell at
  the top of the Earths interior.

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The Earths Atmosphere
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The Earths Interior
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Questions

• 1. The Earth's actual shape is most correctly
  described as
• a. a circle c. an oblate sphere
• b. a perfect sphere d. an eccentric
  ellipse
• 2. The best evidence that the Earth has a
  spherical shape is provided by
• a. photographs of the Earth taken from space
  satellites
• b. the amount of daylight received at the North
  Pole on June 21
• c. the changing orbital speed of the earth in its
  orbit around
• the Sun
• d. the cyclic change of seasons

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Locating Positions on Earth

• Coordinate System
• The latitude-longitude is measured in degrees and
  minutes.
• There are 60 minutes in one degree

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Latitude

• Lines of latitude measure degrees north and
  degrees south, and run left to right. Line of
  latitude are also known as parallels.
• Equator is 0º latitude
• North Pole is 90º N
• South Pole is 90ºS

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Longitude Meridians

• Lines of longitude measure degrees east and
  degrees west, and run up and down. Lines of
  longitude are also known as meridians.
• Prime Meridian is 0º longitude
• International Dateline is 180º longitude

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Questions
1. The diagrams represent four systems of
imaginary lines that could be used to locate
positions on a planet.  Which system is most
similar to the latitude-longitude system used on
the Earth?                                      

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Questions

• 2. From which set of polar and equatorial
  diameters can the actual shape of the Earth be
  inferred?
• 1. polar diameter 12,714 km equatorial
  diameter 12,714 km
• 2. polar diameter 12,756 km equatorial
  diameter 12,756 km
• 3. polar diameter 12,714 km equatorial
  diameter 12,756 km
• 4. polar diameter 12,756 km equatorial
  diameter 12,714 km
• 3. Which layer of the atmosphere contains the
  most water vapor?
• 1. troposphere 2. stratosphere
• 3. mesosphere 4. thermosphere

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• 4. The map shows the location and diameter, in
  kilometers, of four meteorite impact craters, A,
  B, C, and D, found in the United States.  What is
  the approximate latitude and longitude of the
  largest crater?
• 35 N 111 W
• 2. 39 N 83 W
• 3. 44 N 90 W
• 4. 47 N 104 W

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