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populations to deal with stronger and more frequent storms, deadly heat waves,
intense droughts, extended wildfire seasons, and rising sea levels. Other issues
include a lack of clean drinking water for tens of millions of people, and respiratory
distress and illness in large cities like Beijing or Mumbai because of air pollution.
Groundwater supplies used for irrigating crops in the U.S. Midwest are being
depleted. Even aquifers in the east, which receive ample rainfall for recharge, are
still being depleted around population centers like Washington, D.C. because of
overuse (Soeder et al. 2007).
Climate change is a critically-important issue affecting the environment of the
Earth, but by the same token, it is not the only critical issue. It is important to not
lose sight of the many other environmental challenges facing humanity and the
world. However, climate change is overarching, and fixing the other challenges
without addressing climate will sooner or later make all environmental improvements moot.
9.1 The Sixth Mass Extinction
Geologists divide the history of the Earth into a variety of time periods, based on
rock types, localities, the distinctive plants and animals that were around, or the
mass extinction events that have happened several times in Earth history (the demise
of the dinosaurs being only one such example). The naming of individual time intervals has an interesting history beginning with James Hutton. Hutton was a physician, chemist, and farmer in eighteenth century Scotland who essentially invented
the science of geology.
Based on religious scripture, most eighteenth century scholars considered the
Earth to be around 6000 years old. In fact, after detailed analysis of the Bible,
Archbishop James Ussher of Ireland announced in 1650 that the Earth had been
created on the evening of October 22, 4004 B.C. His date was accepted for nearly
two centuries.
Early geological naming schemes were based on biblical tales of Noah’s Ark and
the notion of a worldwide Great Flood. Thus, the original rocks that formed when
the Earth was created were called “Primary.” Sediments that were deposited after
the creation of the Earth but before the Great Flood were called “Secondary.”
Sediments from the flood itself were deemed “Tertiary,” and sediments deposited
after the floodwaters receded were labeled “Quaternary.” Fossils were thought to be
the remains of animals that had perished in the flood. Despite the many changes and
advances in geological science since then, the terms Tertiary and Quaternary are
still used in the geologic time scale to this day, preserving a bit of this history.
The idea of a global flood event fell out of favor with eighteenth century scientists
when no one could explain where all the water came from or where it went, and no
real evidence of such a flood could be found in the geologic record. The melting
continental ice sheets during the transition from the last ice age into the present
interglacial period raised sea level by roughly 400 ft. (122 m) and may have been
9.1 The Sixth Mass Extinction
populations to deal with stronger and more frequent storms, deadly heat waves,
intense droughts, extended wildfire seasons, and rising sea levels. Other issues
include a lack of clean drinking water for tens of millions of people, and respiratory
distress and illness in large cities like Beijing or Mumbai because of air pollution.
Groundwater supplies used for irrigating crops in the U.S. Midwest are being
depleted. Even aquifers in the east, which receive ample rainfall for recharge, are
still being depleted around population centers like Washington, D.C. because of
overuse (Soeder et al. 2007).
Climate change is a critically-important issue affecting the environment of the
Earth, but by the same token, it is not the only critical issue. It is important to not
lose sight of the many other environmental challenges facing humanity and the
world. However, climate change is overarching, and fixing the other challenges
without addressing climate will sooner or later make all environmental improvements moot.
9.1 The Sixth Mass Extinction
Geologists divide the history of the Earth into a variety of time periods, based on
rock types, localities, the distinctive plants and animals that were around, or the
mass extinction events that have happened several times in Earth history (the demise
of the dinosaurs being only one such example). The naming of individual time intervals has an interesting history beginning with James Hutton. Hutton was a physician, chemist, and farmer in eighteenth century Scotland who essentially invented
the science of geology.
Based on religious scripture, most eighteenth century scholars considered the
Earth to be around 6000 years old. In fact, after detailed analysis of the Bible,
Archbishop James Ussher of Ireland announced in 1650 that the Earth had been
created on the evening of October 22, 4004 B.C. His date was accepted for nearly
two centuries.
Early geological naming schemes were based on biblical tales of Noah’s Ark and
the notion of a worldwide Great Flood. Thus, the original rocks that formed when
the Earth was created were called “Primary.” Sediments that were deposited after
the creation of the Earth but before the Great Flood were called “Secondary.”
Sediments from the flood itself were deemed “Tertiary,” and sediments deposited
after the floodwaters receded were labeled “Quaternary.” Fossils were thought to be
the remains of animals that had perished in the flood. Despite the many changes and
advances in geological science since then, the terms Tertiary and Quaternary are
still used in the geologic time scale to this day, preserving a bit of this history.
The idea of a global flood event fell out of favor with eighteenth century scientists
when no one could explain where all the water came from or where it went, and no
real evidence of such a flood could be found in the geologic record. The melting
continental ice sheets during the transition from the last ice age into the present
interglacial period raised sea level by roughly 400 ft. (122 m) and may have been
9.1 The Sixth Mass Extinction