Information
Sheet No
5
Landscape
The rocks of the Burren
The Earth is a dynamic planet. Its surface, and its interior, are constantly changing. One of the effects of this is the formation of new rock.
Rocks are formed in three ways:
1. Through the laying down of sediment particles and the remains of plants and animals (PRODUCES SEDIMENTARY
ROCKS, e.g. limestone, mudstone, sandstone)
2. Through the melting of existing rocks deep underground and from volcanic activity
(PRODUCES IGNEOUS ROCKS, e.g. granite, basalt)
3. Through the distortion of existing rocks deep underground (PRODUCES
METAMORPHIC ROCKS, e.g. slate)
Weathering of
Rocks at Surface
Erosion &
Sediment
Transport
Deposition of Sediment
Burial &
Compaction
Igneous Rock
Crystallisation of Magma
Melting
Uplift
Metamorphic Rock
Sedimentary Rock
Metamorphic Rock
Deformation &
Metamorphism
section Module B 3
How the rocks of North Clare were formed
All of the rocks in North Clare are
SEDIMENTARY ROCKS. They underwent four major stages to produce the rock formations we see on the surface today.
Step 1. Sediment particles such as silt, clay and parts of plants and animals were deposited on the sea floor. These sediments would have been quite soft and pliable.
Step 2. The sediments were buried as more sediment was laid down on top. The sediments were compacted, the particles were pushed closer together and water was squeezed out.
The particles became cemented together as salts formed in between them. At this point, the sediments had been turned into rock.
Step 3. The rocks of North Clare were gradually uplifted (pushed upwards) by tectonic forces.
Step 4. The rocks of North Clare were exposed at the Earth’s surface and were eroded and weathered by wind, rain and temperature changes. This is why there are no siltstones, sandstones or shales in the north part of the
Burren. They have been eroded away exposing the older, underlying limestones.
million years ago
50
0 400
350
300
250
200
150
100
Laid down on the sea floor
Uplifted by tectonic forces
Exposed at the Earth’s surface

Information
Sheet No
6
Landscape
The rocks of the Burren
section Module B 3
During the Carboniferous Period, in Earth’s history (between 359 and 299 Ma*), the land that would become Ireland was located 10ºS of the equator (Ref: Module A1 Information Sheet
No. 4).
The Carboniferous limestones of the Burren
(and Ireland), were formed in a warm, shallow, tropical sea. This sea was similar to the Bahamas or Persian Gulf today.
The sea was full of marine life such as corals and shellfish.
When these marine animals and plants completed their natural life cycle and died, their remains floated down to the sea floor. Their soft body parts rotted away over time, leaving the hard skeletons.
At the same time particles of calcium carbonate, deposited out of the sea water, were also building up in layers on the sea floor. The hard skeletons of the marine plants and animals became embedded in the layers of calcium carbonate. Over a long time these layers compacted to form limestone and the skeletons of the organisms became fossilised within those rocks.
Around 326 Ma, the sea deepened very rapidly.
The formation of the limestone ended abruptly, as it can only be formed in shallow seas, where the light reaches the sea floor.
Only about 500m of the Burren limestone is visible on the surface. We have to go down another 300m before we reach the base. It took approximately 20 million years for all this limestone to form.
* Mega Annum, or millions of years
Limestones are grey coloured rocks made up mostly of calcium carbonate (lime). They can be dissolved slowly by rainwater.

Information
Sheet No
7
Landscape
The rocks of the Burren
section Module B 3
About 318 million years ago large volumes of silt, fine sand and clay were quickly washed in on top of the shales from large rivers that flowed from the continent to the south west. These sediments formed a massive river delta, similar to the Mississippi today.
Direction of delta movement from ancient continental land mass during late Carboniferous
Between 326 and 318 million years ago, the sea that covered North Clare was deep, dark and quiet; no animals lived there as there was very little oxygen. There was an ancient continent
100–200 km to the south-west (off today’s coast).
As time passed, small amounts of very fine clay particles, originating from rivers located on that far away continent, were carried into the deep sea basin by coastal currents. These clay
The Clare Shales
are finegrained, black coloured rocks that can easily be broken into distinct layers. They lie on top of the limestone in the south
Burren and can be seen at particles settled on the seabed on top of the limestones. They eventually became compacted into black shale rocks (known to geologists as the Clare Shales).
Poulacapple, Slieve Elva and the Fisherstreet cliffs at Doolin.
Area covered by the ancient delta,
316million years ago
This delta covered an area of several hundred square kilometres, and stretched all the way from north Clare (at Doolin) to Limerick and
Kerry.
A river delta
is formed at the mouth
The of a river where it enters the sea. water carried in b y the river breaks shape, giving the appear uprooted tree. The str eams carry clay, as the current of water in the str slows down, these sediments ar e dropped building the delta outwar ds.
Ireland 330 million years ago