FORMATION OF TERRACES
The most distinctive feature of the Burren hills is their
stepped or terraced sides (Fig. 1A). These terraces
formed because the limestone layers are actually separated by thin bands of mudstone (clay), that are 15 50 cm thick. You almost never see the bands of mudstone in the hills and valleys of the Burren as they are
very soft and are easily washed away by rainwater.
These mudstone layers are visible, though, in the
Aillwee Cave where the rock has been broken recently (Fig. 1B).
Rainwater gradually washes away the layer of mudstone, eating into the hillsides (Fig. 2A, B). You can
see this happening on the west coast of the Burren,
at Ailladie (Fig. iC). This leaves the layer of limestone on top of the mudstone unsupported (Fig.
2C). Eventually, so much of the mudstone layer is
washed away that the overlying layer of limestone
layer on top becomes unstable and eventually collapses (Fig. 2D). This often leaves piles of loose
blocks and boulders at the base of the terrace (Fig.
1D).
Fig. 1. A: Terraces. B: Layer of mudstone in
between the limestones. C: The notch in
this clliff is forming where the seawater is
eating away at the layer of mudstone.
Fig. 2. A: Layers of limestone separated
by thin bands of soft mudstone. B: Rainwater
attacks the mudstone and washes it away. C:
The limestone is now left unsupported and is
unstable. D: The limestone collapses, forming a
terrace.
A
B
C
D