by Robina Barton -
As Shetland receives European Geopark Status, Robina Barton takes a look at Shetland's incredible geology and the work undertaken by Geopark Shetland.
From the highest sheer cliffs in Britain to the best "hands on" exposure of the Great Glen Fault, Shetland is packed with an incredibly varied geology spanning almost 3 billion years. Where else can you walk on an ancient ocean floor, explore an extinct volcano and stroll across shifting sands all in the space of a day?
Shetland can boast all the main rock types found in the Scottish Highlands, except for the ancient sediments, which run down from Cape Wrath to Ullapool. The Scottish Highlands are globally famous for their geology, (it is no coincidence that the pioneers of modern geology came from Scotland), so for such a small area Shetland certainly has a lot to offer.
In fact, Shetland displays the most amazing diversity of geology in an area its size anywhere. The astonishing variety of rocks tell an amazing tale, not just about Shetland, but how the world itself has formed and changed. Epic events like oceans opening and closing and the formation and erosion of mountains, are written into the geological record of these islands and you don't have to be an expert to see them.
A geological journey
Shetland has been on an incredible geological journey, from close to the South Pole across the equator to its current position at the crossroads of the North Atlantic. Over hundreds of millions of years the climate and landscape have changed dramatically many times and echoes of these past environments have been literally set in stone. Who would have thought that this tiny windswept archipelago in the North Sea has played host to tropical seas, volcanoes, deserts, ice ages and ancient rivers?
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, (known as Lewisian Gneiss after the Isle of Lewis, where it is commonly found). 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 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.
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.
World famous wildlife
The Shetland landscape of today is home to an amazing biodiversity. Over one million seabirds inhabit the cliffs and moorland, with 70 different species breeding in the isles and over 430 migratory species recorded. Many nest on the spectacular sea cliffs, such as those at Noss where erosion of the Old Red Sandstone cliffs has created stone ledges that make ideal nesting sites for a large Gannet population.
Shetland's moorland is predominantly blanket bog, a globally rare habitat. The moorland provides breeding grounds for Great and Arctic Skuas, Snipe, Whimbrel, Dunlin, Golden Plover, and Red-throated Divers. Where drainage is better, a drier heathland is found, while the serpentine rocks of Unst and Fetlar support a unique herb-rich heathland. At the Keen of Hamar on Unst, the serpentine debris has changed little since the ice receded 12,000 years ago. This environment supports a community of rare Arctic plants, including Edmondston's Chickweed which is unique to Shetland.
Several endemic species have evolved in Shetland, despite the fact it has only been separated from the rest of the UK for around 12,000 years. These include two island races of Wren, several races of Field Mouse and a subspecies of bumblebee.
It is not only plant and animal life that is influenced by geology. It has been fundamental to the development of many aspects of human life in the isles from settlement patterns and building techniques to industries both on and offshore. Due to the lack of trees and abundance of stone, Shetland has some of the best-preserved archaeology in Europe. In addition, aspects of the landscape have been so instrumental to man that Shetland place names often reflect these geological features.
Shetland's cultural and natural heritage is one of its richest assets however its geology was overlooked, until 2004 when the Geopark Shetland Working Group (GSWG) was established. This advisory body is led by Shetland Amenity Trust, the organisation responsible for managing Shetland's bid to become a member of the European Geoparks Network under the name Geopark Shetland.
Following an initial application to the EGN in 2006, Shetland Amenity Trust has developed many initiatives to promote Shetland's unique geology, including geological exhibits, trails, interpretive panels, workshops, talks and lectures. All of this has fed into Shetland's EGN bid and, following a successful assessors' visit in May, Geopark Shetland has just found out they have been accepted as a member.
This is fantastic news for the isles, acknowledging the importance of Shetland's incredible geology and creating opportunities to promote it to an international market and develop partnerships with other members.
The EGN is a network of 35 territories across 13 European countries, which share common aims and are working together in an active and dynamic way to achieve them. The Network was established in 2000, and in 2001 it was formally endorsed by UNESCO.
Geopark Shetland aims to:
- Conserve Shetland's rich geological heritage and demonstrate its clear links with natural and cultural heritage.
- Raise awareness and increase understanding of Shetland's geological heritage.
- Enhance the image of Shetland and promote sustainable development linked to geological heritage and Geotourism.
The multi-agency GSWG includes representatives from Shetland Islands Council, Scottish Natural Heritage, VisitShetland, Shetland Tourism Association, the Association of Shetland Community Councils and various community groups. Along with Shetland Amenity Trust, these organisations work with local communities to develop Geopark initiatives, something which is seen as an essential ingredient for success.
Fun for everyone
To the uninitiated, Shetland's rocks and landscape are striking, but a little interpretation reveals the fascinating stories behind them. You can start your Geological Journey at the Museum and Archives in Lerwick, where displays tell the story of Shetland's formation and demonstrate the fundamental links between geology and the natural and cultural heritage of the islands. Then get out and enjoy it for yourself with a range of trails, exhibits, events and information panels throughout the islands, like the self guide "Shetland's Volcano" trail. Further trails and exhibits are in development for 2010 including a journey to the bottom of an ancient ocean…
Shetland's geology is also an impressive resource for learning at every level. Geopark Shetland is developing Geology based teaching resources with local schools and, given the number of geological phenomena that can be seen over a short period of time, Shetland has huge scope for academic research and makes a great location for student field trips.
Gaining EGN status, and the projects undertaken by Geopark Shetland is only the start of the process of making Shetland a world-class area for Geotourism. To find out more visit: www.geoparkshetland.org.uk or contact: email@example.com
Posted in: Exploring Shetland