10/9/2014 8:49:00 PM
Johnnie Hayes, Radley College
The geological features around Durness in Sutherland, Scotland
North West Highland Geopark
In August this year, I visited Balnakeil near Durness in the North West
Highland Geopark. The North West Highland Geopark is Scotland’s first
geopark, having being awarded UNESCO geopark status in 2004. It
contains some of the world’s oldest rocks at 3 billion years old. It covers
770 square miles and it is located in the north west of Scotland.
Durness
Balnakeil, where I stayed.
Durness has some unique limestone called Cambro-Ordovocian Durness
group carbonates, though it is commonly known as the Durness
limestone. It is a pale and dark grey limestone that is around 480 million
years old. The limestone contains a large number of fossils and chert
nodules. Chert nodules are sub-spherical masses of rock with a similar
composition to silica. The limestone was formed by the compaction of
sediment that was deposited in a low energy shallow marine environment.
It formed in an area where there was little or no wave action. The
limestone creates spectacular lochs, which are very popular for anglers
due to the clear waters.
The U shaped valleys that are found in the area were formed by glaciers
in the last ice age. The weight and the movement of glaciers deepened
and rounded river valleys creating the U shaped valleys visible today.
Lewisian gneiss is found in the area and it is among the oldest rocks at
around 3 billion years old as shown in the geological map above. It is a
Precambrian metamorphic rock. The rock is a highly metamorphosed and
folded igneous rock.
These rocks in the Durness area have been dropped down a few hundred
metres by faults, which have saved the rocks from erosion.
Smoo Cave
I visited the very famous Smoo cave. The cave is made of Durness
limestone and it is surrounded by gneiss and quartzite. The cave was
divided into 2 chambers. The first chamber was the large opening, which
was formed by wave action. The back of the chamber showed signs of
recent collapse. The second chamber is split into 2 sections. This chamber
was formed by the action of fresh water. Sadly, the second part of the
chamber was cordoned off for safety reasons due to flooding so I could
not see it. However, the first section was a fascinating spectacle with the
river Alt Smoo dropping down a deep sinkhole into the second chamber
creating an underwater waterfall. Smoo cave formed by the erosion along
a fault by the river and the sea. It is essentially 2 separate caves that
were formed by different mechanisms that joined together over time. The
inlet in front of Smoo cave was formed as the cave roof progressively
collapsed at the cavern deepened.
Faraid Head
Faraid head has some spectacular sand dunes and the largest found
slightly inland. The largest are 60 metres high and the sand dunes were
formed by strong head winds, which the headland is exposed to. Faraid
head also showed evidence of the Moine Thrust belt as the sandstones of
Balnakeil beach have been metamorphosed in schist due to being carried
over a thrust. This thrust fault was located right next to where I was
staying and it was extraordinary to see the change in geology either side
of the fault. The Moine Thrust belt was discovered in 1907 and it was one
of the first thrust belts to be found.