| The Ice
Ages |
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| Since the earliest rocks
around Abercrave ( Abercraf ) were formed over half a billion years ago,
the Earth's climate has fluctuated between long warm
periods when the World was free of ice, and cold ice ages
when the ice extended from the poles into what we now
know as temperate regions. These ice ages occurred around
every 200 million years and lasted for tens of millions
of years .During an ice
age glaciers advance and retreat a number of times, and
although we are presently in an ice age we are in a
warmer interval between periods of advanced glaciation. |
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Twenty such periods of advanced glaciation have already
occurred in this present ice age and the last one which
was at its most severe twenty thousand years ago is often
referred to as the last ice age. At
such times the ice from the Northern Polar Region extends
far enough South to cover Wales and Britain, and the Abercrave region been subjected to glaciation at different
times in the past. The glaciers scoured the land changing
the surface features so that they show the typical
characteristics of a glaciated past.
The
picture on the left shows a glacier "in action"
today scouring material from the rocks as it slowly flows
down the mountain.
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| The picture below shows a close up of the exposed rock surface after the
glacier has retreated leaving flow marks (scratches and
gouges) which clearly show the direction of the
glacier's movement. Huge boulders are often transported
by glaciers which then retreat to leave them perhaps
hundreds of miles from their place of origin. Some of the
boulders and loose rocks around Abercrave are therefore
from other places far to the North.
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Any remains of the large
animals, Dinosaurs and Reptiles, which appeared much
later than the last sedimentary rock formations of the
late Carboniferous and Permian periods, were probably
destroyed by glaciation throughout Wales. Without doubt
these creatures colonised the area, but in the few cases
where their remains may have become buried in mud, sand,
or peat the advancing glaciers of the more recent ice
ages probably destroyed them. The
geology of the Abercrave area is a record of the Palaeozoic Era, when life first appeared in the seas until the
earliest mammal like creatures began to colonise the land.
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The Abercrave area today with its
temperate climate, lush green valleys, rivers,
waterfalls, lakes, caves and mountains owes the variety
of its scenery and natural features to its dynamic
geological past.
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