Page 52 - Environment: The Science Behind the Stories

Figure 2.14 Life thrives in darkness around hydrothermal
Figure 2.13 Geyser in the Black Rock Desert of Nevada. vents on the ocean floor. Vents send spouts of hot, mineral-rich
Geysers propel scalding water into the air, powered by geothermal water into the cold blackness of the deep sea. Specialized biological
energy from deep below ground. The bright colors of the rocks are communities thrive in these unusual conditions, where organisms,
from colonies of bacteria that thrive in the hot, mineral-laden water. such as the giant tubeworms is this image, survive thanks to
bacteria that produce food from hydrogen sulfide through the
Geothermal energy also powers process of chemosynthesis.
Earth’s systems
Chemosynthesis occurs in various ways, but note how
Although the sun is life’s primary energy source, it is not the this particular reaction for chemosynthesis closely resembles
only one for our planet. A minor additional energy source is the photosynthesis reaction. These two processes use different
the gravitational pull of the moon, which in conjunction with energy sources, but each uses water and carbon dioxide to
the sun’s pull causes ocean tides (p. 445). Another significant produce sugar and a by-product, and each produces potential
energy source is geothermal heating emanating from inside energy that is later released during respiration. Energy from
Earth, powered primarily by radioactivity (p. 42). Radiation chemosynthesis passes through the deep-sea-vent animal com-
from radioisotopes deep inside our planet heats the inner Earth, munity as heterotrophs such as clams, mussels, and shrimp
and this heat gradually makes its way to the surface. There it gain nutrition from chemoautotrophic bacteria. Hydrothermal CHAPTER 2 • E ART h’s Physi CAL
heats magma that erupts from volcanoes, drives plate tectonics vent communities excited scientists because they were novel
(p. 52), and warms water, which in some locations shoots out and unexpected, and they showed just how much we still have
of the ground in the form of geysers (Figure 2.13). In places to learn about the workings of our planet.
such as “The Geysers” region of northern California, this
geothermal energy can be harnessed to produce electricity.
Although we harness geothermal energy for our own use Geology: The Physical Basis
today, geothermal energy was powering biological communi- for Environmental Science
ties long before people appeared on Earth. On the ocean floor,
jets of geothermally heated water— essentially underwater gey- If we want to understand how our planet functions, a good
sers—gush into the icy-cold depths. In one of the more amaz- way to start is to examine the rocks, soil, and sediments
ing scientific discoveries of recent decades, scientists realized beneath our feet. The physical processes that take place at and
that these hydrothermal vents can host entire communities of below Earth’s surface shape the landscape around us and lay
specialized organisms that thrive in the extreme high-tempera- the foundation for most environmental systems and for life. s ys TE m s: mATTER , E NER gy, AN d
ture, high-pressure conditions. Gigantic clams, immense tube- Understanding the physical nature of our planet also ben-
worms, and odd mussels, shrimps, crabs, and fish all flourish in efits our society, for without the study of Earth’s rocks and the
the seemingly hostile environment of near-scalding water that processes that shape them, we would have no copper, iron, or
shoots out of tall chimneys of encrusted minerals (Figure 2.14). steel for our industries, products, and technologies; no energy
These locations are so deep underwater that they com-
pletely lack sunlight, so the energy flow of these communi- from fossil fuels; no uranium for nuclear power plants; and no
geothermal power generation. These are just a few examples
ties cannot be fueled through photosynthesis. Instead, bacteria of how we draw on resources and processes from beneath the
in deep-sea vents use the chemical-bond energy of hydrogen surface of our planet and put them to use in our everyday lives. gE o L ogy
sulfide (H S) to transform inorganic carbon into organic car- Our planet is dynamic, and this dynamism is what moti-
2
bon compounds in a process called chemosynthesis:
vates geology, the study of Earth’s physical features, processes,
6CO + 6H O + 3H S S C H O + 3H SO and history. A human lifetime is just a blink of an eye in the
2 2 2 6 12 6 2 4
(sugar) long course of geologic time, and the Earth we experience is 51

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