MEASURING EARTH

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TOPIC 2

• MEASURING EARTH

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USING THE ESRT

• Selected Properties of Earths Atmosphere p.14

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• Average Chemical Composition of Earths Crust,
  Hydrosphere, and Troposphere. p.11

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• Inferred Properties of Earths Interior. p.10

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2.1 Size and Shape of Earth
oblate spheroid
equatorial diameter 12,756 km - polar
diameter 12,714 km
42 km
42 km 12,756km
x 100
x 0.3

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Evidence for Earths Shape.

• Photographs taken from space.
• Ships appear to sink as they pass the horizon.
• Earths shadow on the moon during a lunar eclipse.

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Earths Surface

• Mount Everest
• 8,848 m above sea level.

8,848 m 8.8 km
Earths diameter 12,756 km
8.8 km / 12,756 km
0.07
8.8km 12,756km
x 76 in

x 0.05in
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3 Spheres of Earth
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• The Atmosphere

Atmospheric gases scatter blue light more than
other wavelengths, giving the Earth a blue halo
when seen from space.
The original atmosphere may have been similar to
the composition of the solar nebula and close to
the present composition of the Gas Giant planets,
though this depends on the details of how the
planets condensed from the solar nebula. That
atmosphere was lost to space, and replaced by
compounds outgassed from the crust or (in some
more recent theories) much of the atmosphere may
have come instead from the impacts of comets and
other planetesimals rich in volatile materials.
The oxygen so characteristic of our atmosphere
was almost all produced by plants (cyanobacteria
or, more colloquially, blue-green algae). Thus,
the present composition of the atmosphere is 79
nitrogen, 20 oxygen, and 1 other gases.
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Hydrosphere
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Lithosphere