Tourism is important to both archipelagos, with their distinctive prehistoric ruins playing a key part in their attraction, and there are regular ferry and air connections with mainland Scotland.

[12] Middle Devonian basaltic volcanic rocks are found on western Hoy, on Deerness in eastern Mainland and on Shapinsay.

[14] Glacial striation and the presence of chalk and flint erratics that originated from the bed of the North Sea demonstrate the influence of ice action on the geomorphology of the islands.

The Shetland Islands are the northern outpost of the Caledonian orogeny, and there are outcrops of Lewisian, Dalriadan and Moine metamorphic rocks whose histories are similar to those of their counterparts on the Scottish mainland.

Shetland's most distinctive geological feature is the ultrabasic ophiolite, peridotite and gabbro on Unst and Fetlar, which are remnants of the Iapetus Ocean floor.

[17] Geological evidence shows that, sometime around 6100 BC, a tsunami caused by the Storegga Slides hit the Northern Isles (as well as much of the east coast of Scotland), and may have created a wave of up to 25 metres (82 ft) high in the voes of Shetland, where modern populations are largest.

[18] The Northern Isles have a cool, temperate climate that is remarkably mild and steady for such a northerly latitude, due to the influence of the surrounding seas and the Gulf Stream.

[28] The Knap of Howar Neolithic farmstead on the island of Papa Westray is probably the oldest preserved house in northern Europe.

[36][37] The culture that built the brochs is unknown, but by the late Iron Age the Northern Isles had become part of the Pictish kingdom.

One of the best examples of these stones is on the Brough of Birsay: It depicts three warriors with spears and sword scabbards, as well as characteristic Pictish symbols.

According to the Orkneyinga Saga, Vikings then made the islands the headquarters of the pirate expeditions they carried out against Norway and the coasts of mainland Scotland.

Jon Haraldsson, who was murdered in Thurso in 1231, was the last of an unbroken line of Norse jarls,[49] and thereafter the earls were Scots noblemen of the houses of Angus and St.

[50] In 1468 Shetland was pledged by Christian I, in his capacity as King of Norway, as security against the payment of the dowry of his daughter Margaret, betrothed to James III of Scotland.

In 1470 William Sinclair, 1st Earl of Caithness ceded his title to James III and the following year the Northern Isles were directly annexed to Scotland.

An influx of Scottish entrepreneurs helped to create a diverse and independent community that included farmers, fishermen and merchants that called themselves comunitatis Orcadie and who proved themselves increasingly able to defend their rights against their feudal overlords.

The harsh climate of Orkney and the Orcadian reputation for sobriety and their boat-handling skills made them ideal candidates for the rigours of the Canadian north.

For example, on Shapinsay over 3,048 tonnes (3,000 long tons) of burned seaweed were produced per annum to make soda ash, bringing in £20,000 to the local economy.

[61] Agricultural improvements beginning in the 17th century coincided with the enclosure of the commons and in the Victorian era the emergence of large and well-managed farms using a five-shift rotation system and producing high-quality beef cattle.

[62] There is little evidence of an Orcadian fishing fleet until the 19th century but it grew rapidly and 700 boats were involved by the 1840s with Stronsay and then later Stromness becoming leading centres of development.

[63][Note 1] Many Orcadian seamen became involved in whaling in Arctic waters during the 19th century, although the boats were generally based elsewhere in Britain.

During World War I the 10th Cruiser Squadron was stationed at Swarbacks Minn in Shetland and during a single year from March 1917 more than 4,500 ships sailed from Lerwick as part of an escorted convoy system.

[69][70] The problem of a declining population was significant in the post-war years, although in the last decades of the 20th century there was a recovery and life in the islands focused on growing prosperity and the emergence of a relatively classless society.

There are frequent charter flights from Aberdeen to Scatsta near Sullom Voe, which are used to transport oilfield workers and this small terminal has the fifth largest number of international passengers in Scotland.

[89] Taxes from the oil have increased public sector spending in Shetland on social welfare, art, sport, environmental measures and financial development.

[95] This has been described as "the first of its kind in the world set up to provide developers of wave and tidal energy devices with a purpose-built performance testing facility.

[101] Notable exponents of Shetland folk music include Aly Bain and the late Tom Anderson and Peerie Willie Johnson.

Thomas Fraser was a country musician who never released a commercial recording during his life, but whose work has become popular more than 20 years after his untimely death in 1978.

Since 1468-1469, after Orkney and Shetland were absorbed by the Kingdom of Scotland, Norn gradually began to fade as the influx of Scots-speaking settlers migrated to the islands.

[120] The Norse retained the earlier root but changed the meaning, providing the only definite example of an adaption of a pre-Norse place name in the Northern Isles.

Haswell-Smith (2004) suggests the root may be hjalpandis-øy (helpful island) due to the presence of a good harbour, although anchorages are plentiful in the archipelago.