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Lewisian Gneiss - Rhiconich, Scotland. The main metamorphic event in the Central Region was the 2.5 Ga granulite facies Badcallian event. The Northern Region lacks evidence of granulite facies and in the Southern Region an earlier 2.73 Ga event is recognised locally.
Lewisian gneiss at Assynt. The Northwest Highlands were, and still are, remote and difficult to access. Along a coastal strip some 200 kilometres (120 mi) long and 15–25 kilometres (10–15 mi) wide the terrain is austere with isolated mountains rising above barren lower ground where knolls of bare rock lie among lochans and peat bogs.
The geology of the Isle of Skye in Scotland is highly varied and the island's landscape reflects changes in the underlying nature of the rocks. A wide range of rock types are exposed on the island, sedimentary , metamorphic and igneous , ranging in age from the Archaean through to the Quaternary .
In addition, there are shorter rows of stones to the west-southwest, south and east-northeast. The stones are all of the same rock type, namely the local Lewisian gneiss. Within the stone circle is a chambered tomb to the east of the central stone. [5]
The Lewisian gneiss is found throughout the Outer Hebrides of Scotland, on the Scottish mainland west of the Moine Thrust, and on the islands of Coll and Tiree. [20] These rocks are largely igneous in origin, mixed with metamorphosed marble, quartzite and mica schist with later intrusions of basaltic dikes and granite magma. [21]
An outcrop of gneiss on Rona. Rona is an extension northward of the ridge of Raasay. Its geology is Lewisian gneiss and the glaciated landscape is underlain by some of the oldest rocks in western Europe.
The oldest rocks of Scotland are the Lewisian gneisses, ... This is composed of a wide variety of materials, including mica schist, biotite gneiss schist, ...
Lewisian Gneiss – Metamorphic rocks, ranging from pink to grey-green in colour, depending on the rock they were originally formed from. Around 3,000 million years old, making them the oldest rocks in Britain, and, along with similar rocks in Bulgaria , Finland , the Lofoten Islands of Norway , and Russia , among the oldest in Europe.