The geological history of Leitrim and Cavan
The geological
history of Leitrim
and Cavan is one of
lost oceans, tropical
coral reefs,
immense collisions
of continents and
unimaginable
kilometre thick
Ireland was just below the equator 330 million years ago.
sheets of ice. It is a
seven hundred million year old story written in rocks that make up the
region. Leitrim and Cavan is part of the world’s great tectonic plates,
those sections of the world’s crust, which make up the continents and
seas. Plates can move apart or collide.
The movement of tectonic plates is
incredibly slow, typically a few
centimetres per year. Over millions of
years Leitrim and Cavan drifted from
near the South Pole to its present
latitude in the north. As it has floated
Limestone is formed by the
north it has met a range of different
compression of fish bones and shells
climates and environments and each of
them has helped develop the landscapes we see today. Three hundred
and thirty million years
ago, during a period of
geological time known as
the Carboniferous period
Leitrim and Cavan lay just
below the equator and
basked in a hot tropical
climate. Ireland was
entirely covered by sea at
this stage. Fish died, mostly shellfish and were compressed by mud and
made a rock called limestone. During another stage great rivers flowed
over our area. The sand in the rivers was compressed and made
sandstone. Mud was also compressed to form shale. Later when plates
collided they pushed up the limestone, shale and sandstone and formed
the mountains in our area. That is why the mountains in our locality are
made of limestone, shale and sandstone.