Geology Reference
In-Depth Information
Fossilizing carbon fuels
Concern about modern climate change has people talking about reducing the use of
fossil
or
carbon
fuels. Both terms refer to coal and oil resources, many of which are
found in Carboniferous rock layers created during the late Paleozoic. The abundant
plant and animal life in the Carboniferous period left its carbon remains to form geologic
deposits in rock layers of coal. In fact, geologists describe these mid- to late- Paleozoic
environments as
coal swamps.
(Some coal swamp deposits were formed during the fol-
lowing period, the Mesozoic, which I describe in Chapter 20.)
A rock sequence common in the Carboniferous period, especially the
Pennsylvanian period, is called a
cyclothem.
Cyclothem rock layers indicate a
transition between marine and nonmarine environments, similar to what is ob-
served today at a low-lying river delta such as the Mississippi River. These regions
are now (and were in the Carboniferous period) full of thick, swampy vegetation.
As these plant materials die, become buried by sediments, and accumulate over
time, they turn into coal beds.
The cyclothems of the Carboniferous are so widespread that geologists are still seeking
answers to how they were formed because it seems unreasonable that so much of the
earth was covered in swampy, transitional marine environments.
Pangaea, the most super of supercontinents
By the end of the Paleozoic, all the major continents on earth came together, forming a
single supercontinent. Pangaea is the most super of supercontinents because there is no
evidence that ever before — or ever since — all the major landmasses formed a single
continent. In Chapter 8, I explain that the remains of Gondwana, the southern landmass
of Pangaea, led early geologists to ask the questions that eventually led to the theory of
plate tectonics.
To find out what happens when the supercontinent Pangaea breaks apart in the Mesozo-
ic era, be sure to read Chapter 20.
