Geology Reference
In-Depth Information
sil remains were found on both sides of the Atlantic could have
walked from one side to the other, taking with them the seeds
of plants and trees, the fossils of which were also found on both
sides. It did not seem such an unreasonable idea but for the
huge distances involved, and the extraordinary fit of the two
continents.
One of Wegener's strongest arguments in favour of his theory
was that when the continents were reconstructed in this way
then an ancestral equator could be traced right across Pangaea
from the fossils typical of a tropical environment, such as those
which had prevailed during the formation of the coal fields of
Britain and many other countries during the Carboniferous. The
inference from this was that Britain had lain close to the equa-
tor during the Carboniferous, as part of Pangaea, and had been
drifting northwards ever since Pangaea split up. In a similar way,
evidence for past glaciations of the same age was also found on
many continents that were now thousands of miles from the
poles and each other, giving further strength to the Wegener
hypothesis. This remarkable theory seemed to explain so many
geological conundrums, but the concept that continents could
drift helplessly around the world covering many thousands of
miles, when they seemed to be so solid and stationary, was so
preposterous that the majority of geologists just could not
accept it.
Apart from the obvious di~culties it posed, the main obstacle
to accepting the theory was the lack of a mechanism which
could physically move continents large distances. Wegener visu-
alised the continentals blocks as slabs of granite and gneiss
which, being rich in the lighter elements, floated in a sub-
stratum (now known as the mantle) containing the heavier
elements, but he was unable to come up with any convincing
driving force that would move these slabs around. As one oppo-
nent succinctly put it: 'We are invited to think of a continental
mass under almost no horizontal forces ploughing its way
steadily through an ocean floor, which resists its advance
