usually rendered with a curled tail: ⟨ʒ⟩) hence , the form used in the name of the pre-1975 county council. This is also the source of the ZE postcode used for Shetland. Most of the individual islands have Norse names, although the derivations of some are obscure and may represent pre-Norse, Pictish, or even pre-Celtic names or elements. Geography and geology Shetland is around north of Great Britain and west of Bergen, Norway. It covers an area of and has a coastline long. Lerwick, the capital and largest settlement, has a population of 6,958 and about half of the archipelago's total population of 22,920 people live within of the town. Scalloway on the west coast, which was the capital until 1708, has a population of fewer than 1,000 people. Only 16 of about 100 islands are inhabited. The main island of the group is known as The Mainland. The next largest are Yell, Unst, and Fetlar, which lie to the north, and Bressay and Whalsay, which lie to the 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 west of Walls, Fair Isle 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 the world of an Iron Age broch; Noss to the east of Bressay, which has been a national nature reserve since 1955; St Ninian's Isle, connected to Mainland by the largest active tombolo in the United Kingdom; 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, Dalradian and Moine metamorphic rocks with histories similar to their equivalents on the Scottish mainland. There are also Old Red Sandstone deposits and granite intrusions. The most distinctive feature is the ophiolite in Unst and Fetlar which is a remnant of the Iapetus Ocean floor made up of ultrabasic peridotite and gabbro. Much of Shetland's economy depends on the oil-bearing sediments in the surrounding seas. Geological evidence shows that in around