Jurassic
Climate and Tectonic Activity
Pangea,
which had begun forming in the Devonian (400 million
years ago) and lasted through the Triassic, finally
began to split apart in the Late Triassic. By the Middle and Late
Jurassic, enough plate movement had occurred to separate South America
from southern Africa. Laurasia (which consisted of
North America and Eurasia) also moved away from Africa and South America,
helping to create the Atlantic Ocean and the Gulf of Mexico. Volcanic
activity was common along these rifting continental margins. At the
same time, Eurasia (Europe and Asia) moved to the south and started
to close off the Tethys Ocean. Sea level gradually rose during the
Jurassic, creating epicontinental seaways in North America and Europe.
The end result was a world with many more separate land-masses, and
a great deal more coastline, than the world of the Triassic.
Much of the Jurassic world was warm and moist, with a greenhouse climate.
Coal deposits formed under forests in Australia and Antarctica. Although
some arid regions remained, much of the rest of Pangea was lush and
green. Northern (Laurasian) and southern (Gondwanan) biotas were still
distinct in many ways, but by the Jurassic, faunas had acquired a
more intercontinental character. Some animals and plants were now
found nearly worldwide, instead of being restricted to particular
regions.
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