The decay of organic
stuff -- life -- accounts for the fossil fuels coal, gas and oil. What kind
of plants and animals sacrificed their bodies so we can burn gasoline in
our cars and natural gas in our furnaces?
none, we're not going to attempt to Cliff-Note the entire natural history
of fossil fuels on a single web page. But we do want to showcase some
of the fascinating organisms that developed when lots of future oil and
gas was being deposited.
Want more on evolution
the process that explains the diversity of life?
on the "thumbnail" images below (along the right side of the
page) to see a full-size diorama of that time period)
Miocene & Oligocene
The Miocene (5 million years ago -- mya -- to 23 mya) and the Oligocene
(23 mya to 34 mya) Epochs provided about 12.5 percent of known oil and
During the Miocene, grazing mammals increased and proliferated. In this
bear-dog eats three-horned ruminant world, both grazers and predators
gained speed to improve their chances for survival on the grasslands.
The Oligocene was
marked by a blossoming of the mammals. It also contains the first records
of marsupials, in Australia.
The Cretaceous Period, from 141 mya to 65 mya, was dominated by dinosaurs,
which were presumably destroyed by an asteroid
impact at the end of the era. The middle Cretaceous saw major deposits
of organic material that would form oil and gas. About 29 percent of the
total supply was laid down between 119 mya and 88.5 mya.
During the Jurassic (202 mya to 141 mya), dinos ruled, mammals drooled,
and the continents were welded into the supercontinent Pangea. About 25
percent of total oil and gas accumulated during the Jurassic, between
169 mya and 144 mya.
During the Permian (290 mya to 250 mya) and Pennsylvanian (323 mya to
290 mya) Periods, the organic material for 8 percent of today's oil and
gas was deposited.
The therapsid dinosaurs that would later evolve into mammals appeared
in the Permean. These carnivores had differentiated teeth and separate
nostrils. The Permean Period ended with a huge asteroid impact 250 mya
that exterminated 96 percent of all living species. Got that hard hat?
The swampy forests of the warm, damp Pennsylvanian Period supplied major
coal deposits and lots of fossils. Trees grew 100 feet tall, and some
ferns reached 50 feet -- five stories -- in height. Bizarro animals
included meter-long cockroaches and the first reptile.
Between 374 mya and 352 mya, about 8 percent of conventional oil and gas
were deposited. The deposits occurred during the Mississippian (363 mya
to 323 mya) and Devonian (409 mya to 363 mya) Periods.
In the Mississippian, land was gathered into two large continents. The
northern continent, comprising North America, Europe and Asia (less
India) was called Laurasia, and was surrounded by seas filled with crinoids
The first sharks and bony fishes emerged during the Devonian, along
with the first seed-bearing plants. Amphibians moved to land, becoming
the first vertebrates to know the pleasure of stepping onto solid ground.
Take it from us: Terra firma feels great if you've been seasick for
a hundred million years...
During the Silurian Period (439 mya to 409 mya), about 9 percent of oil
and conventional gas were deposited. Meanwhile, life was busy test-driving
a number of cool inventions. Aquatic plants made ozone, offering protection
from the sun's ultraviolet rays and allowing organisms to abandon
the protection of the sea and head for dry land. Insects evolved -- leading
to endless cussing over house flies and mosquitoes.
The first plants with vascular channels -- pipes that carry water and
nutrients -- appeared. Fish with jaws arose (all the better to eat you
with, my dear) which eventually spawned modern vertebrates.
Back to the
subject: How do they find oil left by these creatures,