Geology

Shetland’s geology spans almost 3 billion years and is more diverse than any similar sized area in Europe.

With rocks of every era from the Precambrian to the Carboniferous, Shetland’s geology spans almost 3 billion years and is more diverse than any similar sized area in Europe. Where else can you walk on ancient oceanic crust, explore an extinct volcano and stroll across shifting sands in the space of a day?

Over the past 700 million years Shetland has travelled from a location close to the South Pole across the Equator to its current latitude of 60° north. On the journey it experienced oceans opening and closing, mountains forming and eroding, tropical seas, volcanoes, deserts, ice ages and ancient rivers. Evidence of these earth-shaking events can be found throughout the isles, including a number of unique geological features.

Where it all began

600 million years ago, Shetland and Scotland were part of the continent we now call North America. Northern and Western Europe (including England) formed another two continents, and all three were separated by an ocean – the Iapetus Ocean. The ancient North American continent was made partly of gneiss. This rock, seen in northern parts of Shetland today is about 2.8 billion years old! Slowly, the ancient North American continent eroded and thick layers of sand and mud built up on the seabed around its coast.

When continents collide

Tectonic plates carrying the Earth's continents are constantly shifting, (which explains why Shetland was once to be found near the South Pole!) Between 500 and 420 million years ago the North American continent collided with those carrying Northern and Western Europe to form a huge new landmass called Pangaea. The layers of sediment on the seabed, which had now turned into rock, were crumpled during this massive collision. They were forced upwards to form an enormous mountain chain. This Caledonian mountain chain would have been similar in size to the Himalayas we know today.

Death of an ocean

When Pangaea formed, part of the crust (sea-bed) of the Iapetus Ocean and the mantle beneath it were forced up over the top of the North American continental crust. In Unst and Fetlar, to the far north, serpentine rocks that originally formed on this ocean floor were driven up over continental rocks along two major thrusts. An exposed ocean crust is called an ophiolite and they occur very rarely. The Shetland ophiolite has been described as "the most compact, best exposed, complete and accessible in the world" by the late Professor Derek Flinn of Liverpool University.

Pangaea was a vast desert. By 400 million years ago Shetland was lying close to the equator and it experienced a tropical climate that varied from wet and humid to dry and arid – hard to believe today! Streams and rivers ran down from the Caledonian mountains and fed temporary lakes on the desert plain. During wetter periods the lakes could be long-lived and aquatic life evolved and thrived. Sandstones and mudstones built up from layers of sediments in these watery environments. When the creatures of the lake died, they sank to the bottom to be buried among the sediments. The remains of these strange primitive fish would become fossilized, and these fossils can be found today in areas around the south and west Mainland.

Discover ocean floors, volcanoes and shifting sands in a day!

Volcano!

Continental collisions generate massive amounts of heat. This causes rocks to melt and huge amounts of molten magma to build up deep below the surface of the Earth. This is exactly what happened when Pangaea formed. The magma forced its way to the surface as volcanoes. At Eshaness in Northmavine you can walk through "the best section through the flank of a volcano in the British Isles" (the late W. Mykura, Edinburgh University). Here too you can experience the awesome beauty of one of the highest energy coastlines in the world. The west coast of Shetland is blasted by the full force of the North Atlantic. Ferocious storms have carved spectacular cliffs that drop into deep sea, while caves, stacks, arches and geos are commonplace.

A landscape of contrasts

By contrast Shetland contains a stunning inner coast of tranquil voes and sandy beaches. For these, ice is largely responsible. Ice has covered Shetland several times over the past two million years. It was never as deeply buried as Scandinavia or mainland Scotland, so it does not display a similar deep carved landscape. But here, the glaciers gently scoured the landscape into the low, undulating hills and shallow lochs we know today.

Nowadays in Shetland you are never more than 5km from the sea but it wasn't always like this. During glacial times, a large amount of water was locked away as ice, making sea levels considerably lower. Only when the ice began to melt some 12,000 years ago did the seas begin to rise. Much of Shetland became a flooded landscape as the lower ends of its valleys drowned beneath the rising waters. Numerous sea inlets - the "voes" now characteristic of Shetland - were formed. In addition, rising sea levels reworked sediments to produce stunning sandy or shingle beaches, bars and tombolos. The sand tombolo at St. Ninian's Isle is one of the finest in Europe.

Shetland UNESCO Global Geopark

Thanks to its rich and varied earth heritage, Shetland is part of the European Geoparks Network and known as Shetland UNESCO Global Geopark.

Shetland UNESCO Global Geopark brings to life the fascinating stories behind Shetland’s geology and geographical location, as well as demonstrating how these features have influenced every aspect of life in the isles, from the landscape and biodiversity to the settlement patterns and economy.

Begin your geological journey at the Museum and Archives in Lerwick, where displays tell Shetland’s story from its geological beginnings to the present day. From here follow our range of self guided trails and discover stunning geological sites for yourself. You will also find interpretive boards and geo-exhibits along the way to help you uncover this fascinating aspect of Shetland’s heritage.

If you are planning to undertake geological fieldwork in Shetland please do so responsibly (.pdf)

What next?

  • Read more about Shetland's spectacular scenery, including some of the best viewpoints
  • Kayaking is one of the best ways to explore some of Shetland's hidden geological treasures
  • Download a Shetland Heritage leaflet about Shetland geology (.pdf)
  • Read more about Shetland's geology on the Shetland Landscapes website
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