300,000,000
to 10,000 Years Ago |
Wherever you
stand in Allerton or Mossley Hill you are not far
above sandstone bedrock. It is visible in one or
two places and there has been quarrying in the
past, but you are more likely to notice where it
has been used as a construction material for a
variety of buildings and, especially, for the
ancient field boundary walls, many of which have
been preserved in one form or another. |
This is where,
in the distant past, the story begins, for you
stand on what was once an arid desert located
near to the equator. By the start of the Permian
period (300 - 250 million years ago), what
is now England was evolving from a tropical
landscape of luxuriant plant life with a vast
complex of river deltas to an inland desert of
the supercontinent known as Pangea. Sand
had been formed by the action of wind, rain and
rivers over a long period. |
During the Triassic
period (250 - 200 million years ago),
England occupied a position similar to that of
the Sahara Desert today. Internal lakes dried up
forming salt deposits and sandstone was formed by
the pressure of overlying deposits and
cementation of the sand grains caused by the
separation of some of the mineral content. The
oxidation of iron-rich minerals gave the
sandstone its characteristic red colour. In the
early part of this period a large and turbulent
river transported pebbles (mainly quarzite) from
parts of France and deposited them widely over
England. These became embedded in the emerging
sandstone to form what are known as Bunter
Pebble Beds. This is the kind of rock that
underlies Allerton and Mossley Hill in the
present day. |
Folding of the
Earth's crust due to continental drift continued
over the Jurassic (200 - 145 million
years ago) and Cretacious (145 - 66
million years ago) periods. The continental land
masses gradually evolved until, by the Paleogene
period (66 - 23 million years ago), they were
recognisably like those of today. Piled on top of
the rock in Allerton and Mossley Hill these days
is an assortment of clay, pebbles, peat, sand and
gravels formed and transported during the last
Ice Age 110,000 to 12,000 years ago. After the
Ice Age, the surface was further modifed by
decaying vegetation and the action of wind and
water (erosion and flooding). |
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The
Permian, Triassic and Paleogene Periods |
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