Page 58 - Environment: The Science Behind the Stories

QUATERNARY PERIOD sea level rose 17 cm (6.7 in.) in the last
PLEISTOCENE HOLOCENE ANTHROPOCENE ? century and will likely rise by much more
in this century (pp. 516–519). Moreover,
Meters per million years 300 acidifies ocean water
400
Erosion rate
increasing atmospheric carbon dioxide
(pp. 446–447, 506), which kills off coral
200
reefs (and will even likely dissolve some
100
of the geologic strata being formed).
All these changes—along with the
0
500 Atmospheric pollution and habitat disturbance we are
inflicting on Earth’s biotic communities—
Parts per million 300 are causing extinctions of animals and
carbon dioxide
400
plants (pp. 299–301). If we step back to
view our impacts in deep geologic time,
200
motion a rapid new mass extinction event.
100 it becomes clear that we are setting in
8 Human Finally, our recent explosion in popu-
population lation has intensified our impact—changes
6 are happening in the blink of an eye,
Billions 4 geologically speaking. The entire period
of our society’s existence so far could end
2 up represented in as little as a millimeter of
0 rock in the future, so the changes we are
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 bringing about now would appear sudden
Thousands of years before present to a geologist of the far future.
Many scientists resist the idea of
Figure 1 global soil erosion rates (top) and atmospheric carbon dioxide concentrations
(middle) have increased sharply in just the last few hundred years, along with human renaming our current epoch because they
population (bottom). These patterns have persuaded some geologists that we should question whether the proposal holds true
recognize a new epoch in Earth history and call it the Anthropocene. Adapted from Zalasiewicz, to the tradition of defining time periods CHAPTER 2 • E ART h’s Physi CAL
J., et al., 2008. Are we now living in the Anthropocene? GSA Today 18(2), 4–8, Figure 1. based on changes actually seen in the
geologic record. But supporters of the
As greenhouse gas concentra- century (p. 514). Rising temperatures are idea maintain that today’s changes will be
tions rise, so does temperature. Earth’s melting polar ice. The influx of meltwater readily visible in future stratigraphy and
temperature has risen 0.7 °C (1.3 °F) in into the oceans, combined with the fact that we should recognize this unprece-
the past century and is predicted to rise that warmed water expands in volume, dented time of rapid change in Earth’s his-
by 1.8–4.0 °C (3.2–7.2 °F) in the current means that sea level is rising. Global tory by designating it the Anthropocene.

FAQ Technically speaking, is coal a rock?

Coal is a geologic resource of great importance in environ- Geologic and Natural Hazards
mental science, but many people are unsure of what coal is or s ys TE m s: mATTER , E NER gy, AN d
where it comes from. Coal is hard and is found underground, Plate tectonics gives rise to creative forces that shape our
like many types of rocks, so some people would classify it as planet—yet some of the consequences of tectonic movement
a rock. Others, however, argue coal is not a rock because can also pose hazards to us. Earthquakes and volcanoes are
it is the modified remains of organic material, mostly woody examples of geologic hazards. We can see how such hazards
plants, from hundreds of millions of years ago. relate to tectonic processes by examining a map of the cir-
According to geologists, coal is a rock because it is a cum-Pacific belt, or “ring of fire” (Figure 2.20). Nine out of 10
solid aggregation of minerals, particularly carbon. Carbon earthquakes and over half the world’s volcanoes occur along
is classified as a mineral because it is a naturally occurring this 40,000-km (25,000-mi) arc of subduction zones and fault gE o L ogy
solid element with a crystalline structure. Other rocks, such as systems. Like many locations along the circum-Pacific belt,
some types of limestone, also contain the remains of ancient Japan has experienced earthquakes and volcanism frequently
organisms (such as the shells of marine organisms) and are in its past. As a result, it had put precautions in place for such
categorized with coal as organic sedimentary rocks. dangers. 57

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