Shetland - Geography and Geology

Geography and Geology

Shetland is around 170 kilometres (110 mi) north of mainland Scotland, covers an area of 1,468 square kilometres (567 sq mi) and has a coastline 2,702 kilometres (1,679 mi) long. Lerwick, the capital and largest settlement, has a population of around 7,500 and about half of the archipelago's total population of 22,000 people live within 16 kilometres (10 mi) of the town. Scalloway on the west coast, which was the capital until 1708, has a population of less than 1,000.

Out of the approximately 100 islands, only 16 are inhabited. The main island of the group is known as Mainland and of the next largest, Yell, Unst, Fetlar lie to the north and Bressay and Whalsay to east. East and West Burra, Muckle Roe, Papa Stour, Trondra and Vaila are smaller islands to the west of Mainland. The other inhabited islands are Foula 28 kilometres (17 mi) west of Walls, Fair Isle 38 kilometres (24 mi) south-west of Sumburgh Head, and the Out Skerries to the east.

The uninhabited islands include Mousa, known for the Broch of Mousa, the finest preserved example in Scotland of these Iron Age round towers, St Ninian's Isle connected to Mainland by the largest active tombolo in the UK, and Out Stack, the northernmost point of the British Isles. Shetland's location means that it provides a number of such records: Muness is the most northerly castle in the United Kingdom and Skaw the most northerly settlement.

The geology of Shetland is complex, with numerous faults and fold axes. These islands are the northern outpost of the Caledonian orogeny and there are outcrops of Lewisian, Dalriadan and Moine metamorphic rocks with similar histories to their equivalents on the Scottish mainland. Similarly, there are also Old Red Sandstone deposits and granite intrusions. The most distinctive feature is the ultrabasic ophiolite, peridotite and gabbro on Unst and Fetlar, which are remnants of the Iapetus Ocean floor. Much of Shetland's economy depends on the oil-bearing sediments in the surrounding seas. Geological evidence shows that at around 6100 BC a tsunami caused by the Storegga Slides hit Shetland, (as well as the rest of the east coast of Scotland), and may have created a wave of up to 25 metres (82 ft) high in the voes where modern populations are highest.

The highest point of Shetland is Ronas Hill, which only reaches 450 metres (1,480 ft) and the Pleistocene glaciations entirely covered the islands. The Stanes of Stofast is a 2,000 tonne glacial erratic that came to rest on a prominent hilltop in Lunnasting during this period.

Shetland is a National Scenic Area, although unusually this single designated area is made up of a number of discrete locations: Fair Isle, Foula, South West Mainland (including the Scalloway Islands), Muckle Roe, Esha Ness, Fethaland and Herma Ness.