Limestone is a sedimentary rock.
A large area of exposed limestone is known as a Karst Landscape.
The Burren Co. Clare and the Aran Islands;
Formation: during the Carboniferous Geological Period 350 million years ago.
Skeletons of marine life and sea-shells were deposited in layers called bedding
plains on the floor of a shallow tropical sea near the equator.
The remains were compressed by the weight of the overlying deposits and the
weight of the sea.
Calcium Carbonate from the bones of the decayed marine life cemented the
deposits into limestone.
The sedimentary rocks were uplifted and fractured to form joints or cracks;
water follows these cracks.
The Burren has very little surface drainage as limestone is permeable.
The Burren was covered in forests but this was easily removed by early settlers
and led to soil erosion.
Weathering in a Limestone area through Carbonation.
Rainwater falling through the atmosphere absorbs CO2 forming a weak
carbonic acid.
This reacts with calcium carbonate(the cementing agent in limestone) and leads
to the rock breaking down.
This process is called Carbonation.
Surface features:
1. Limestone pavement: e.g. BlackHead Co. Clare
This is a large flat area of limestone exposed on the surface.
Limestone has vertical joints and horizontal bedding planes.
The process of Carbonation attacks the joints, widening them, forming grooves
in the limestone called grikes.
The flat slabs of limestone the grikes are called clints.
They take the appearance of paving slabs.
Small amounts of soil may develop in the grikes allowing rare polar and tropical
plants to grow.
Underground features:
1. Dripstone formations: e.g. the Aillwee cave
Water seeps down through the limestone dissolving it.
When the water reaches the roof of a cavern, the water drips from the ceiling.
It leaves a small deposit of calcite on the roof. Some calcite drips onto the floor
of the cave.
This calcite continues to grow downwards to form a stalactite (it looks like an
icicle).
Stalagmites grow from the floor up as drips with calcite in them fall and splash
on the floor. They tend to have a wider base than the stalactites.
If the 2 dripstone formations join up, they form a pillar.
Due to impurities these dripstone features may have a brownish-yellow colour.