Geology Reference
In-Depth Information
they tend to talk about geology. One of the great geological
debates of the day was the exciting new concept of 'continental
drift' and it inevitably became the topic of conversation.
As early as 1620 Sir Francis Bacon noted the shape of the coast-
lines of South America and West Africa, and wrote: 'Both areas
have similar isthmuses and similar promontories, a fact not due
to mere accident.' Rather like two pieces of a poorly made jig-
saw there were some places where the coastlines overlapped, and
others where there was a gap, but overall the 'fit' was remark-
able. This 'fit' continued to fascinate and ba¬le people for cen-
turies until in 1912 Alfred Wegener, a German astronomer who
later became a meteorologist, came up with the extraordinary sug-
gestion that South America and West Africa had once been joined
together. Not only that, but he also postulated that during the
Carboniferous they were part of one united super-continent,
which Wegener called 'Pangaea', that contained the precursors of
all
the continents we see today. Wegener then argued that during
the Mesozoic, Pangaea had developed numerous fractures and the
resulting continents slowly drifted apart until Cretaceous times
when South America and Africa fully separated and the South
Atlantic opened up between them. Wegener also recognised that
North America separated from Europe much later on.
For many years it had been recognised that the rock forma-
tions and the fossils found on the coasts of both Brazil and West
Africa were identical, although the two countries were now 5000
miles apart on opposite sides of the Atlantic. Fantastic theories
were postulated to explain these phenomena, the most widely
accepted being that of a 5000 mile land bridge which had once
linked the two countries but which had since sunk without trace
into the ocean floor. Citing Panama as an example of a land
bridge which now links North and South America, adherents to
the 'Atlantic land bridge theory' argued that animals whose fos-
