Geology Reference
In-Depth Information
Short wavelength
solar radiation
17.3x10
16
W
Short wavelength
radiation
Long wavelength
radiation
Tidal energy
27.3x10
12
Direct reflection
5.2x10
16
W
Tides, tidal energy, currents, etc.
2.7x10
12
W
Direct conversion to heat
8.1x10
16
W
Winds, ocean currents, waves, etc.
Conduction 21x10
12
W
0.035x10
16
W
Evaporation and precipitation
Water
storage
bank
Submarine volcanism
11x10
12
W
4x10
16
W
Volcanoes, hot springs on land
Plant
storage
bank
Photosynthesis
0.004x10
16
W
0.3x10
12
W
Decay
Organic matter
Earth's thermal energy
32.3x10
12
W
GEOTHERMAL ENERGY
Common
sedimentary rocks
10
26
J
Recoverable fossil
fuels
2.5x1023 J
Thermal energy
1.3x10
27
J to 10
km depth
Uranium and
Thorium withing 1
km of surface
5x10
29
J
Spontaneous
nuclear decay
Fig. 6.1 Energy flow sheet for the surface of the Earth. After Skinner (1986)
sun is not the sole source of energy on Earth. The third and smallest source is tidal
energy produced from the interaction between the gravitational potential energy of
the moon and the Earth's rotation. It accounts for about 3 TW (0.002% of the total
energy budget). The second greatest source, geothermal energy, offers some 23 TW
or 0.013% of the total. This energy reaches the planetary surface in the form of
volcanoes, hot springs or conduction and plays an important role in the rock cycle
(see Fig. 6.11).
Fig. 6.1 shows the energy cycle on Earth according to Skinner (1986), which was
adapted in part from Hubbert (1962).
6.4 Energy from the solid Earth
Two different sources of energy come from the solid Earth. The first is geothermal
energy, which whilst renewable, has found limited application on a global scale. The
second is nuclear energy, coming from the mining of radioactive minerals, particu-
larly uranium isotopes. The latter, although socially and politically controversial,
constitutes a key source of energy for many countries. Both sources of energy will
be explained in detail in the following sections.
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