Gondwana existed from about 550
million years ago until 180 million years ago. It is one of the most well known
super-continents, in the sense that more people have at least heard of it,
rather than individual cratons like Avalonia or Baltica.
If I’m reading the information
correctly, Gondwana existed both before and after Pangaea. Before Pangaea, it
came into being when several cratons stuck together, beginning about 800
million years ago with the formation of the East African Orogeny, which
involved the collision of India and Madagascar with East Africa. Between 600 to
530 million years ago, this group added South America, Australia and
Antarctica, in that order. Thus Gondwana was born.
Eventually, it merged with Laurasia
and became Pangaea, sometime around 335 million years ago. But it wasn’t an
easy relationship, you might say. Pieces of what had formerly been Gondwana
kept breaking off, drifting north to join the former Laurasia section, such as
bits of China and Indo-China. The western edge of Pangaea was beginning to
break up while the eastern edge was trying to collect itself together.
Meanwhile, the formation of Pangaea
and its mountains greatly impacted sea levels and global climate, producing
glaciers and continent-wide sedimentation.
But what about Gondwana? About 175
million years ago, it had had enough and broke away. But it didn’t come out of
it unscathed. Besides the bits that had already drifted to ‘the other side’,
Florida, southern Georgia and Alabama stayed attached to North America.
Once it separated from its partner,
Gondwana just kept falling apart. About 132 million years ago, Antarctica,
Australia, India and Madagascar broke off and then broke up, going their
separate ways. South America slowly broke away from Africa, starting in the
south and going north, but the exact timing is uncertain. It could have started
as early as 190 million years, and finally finished around 85 million years
ago.
So, if you’ve been paying attention,
you’ll realize that most of the cratons that formed Gondwana now inhabit the
southern hemisphere. Its remnants account for about 2/3 of today’s continental
area, including Africa, Antarctica, Arabia, Australia, Indian Subcontinent and
South America.
If I were a paleo-geologist, I might
have made more sense out of the wiki articles I consulted on this subject. The
writer of these articles - particularly the one on Gondwana - seemed to think
that anybody who was looking up this subject must be a student, for he/she/it
kept using names and terms that I - as a lay person - did not know, leading to
much confusion on my part. It seemed far more detailed than I felt I could fit
into a blog, anyway, so I skipped lightly through most of it, looking for the
important details without bogging down the blog.
Paleo-geology was going to be an
elective of mine in college, but I didn’t get that far. Hmm, anybody got a good
used textbook on the subject?
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