Landscape & Heritage

Have you ever wondered why the Mourne Mountains and Slieve Croob rise over a beautiful landscape? The answer lies deep in the prehistory of the earth, beginning when the surface of the earth looked very different.  If you stand in the Deer’s Meadow near Spelga Dam, you are standing on the sedimentary rock formed in the earth’s ancient oceans that once covered the Mourne peaks. It took the shifting of continents, volcanic activity and the effects of the various Ice Ages to shape what we now appreciate as the Mourne AONB. This transformation took millions of years to complete.

The Mourne Mountains contain twelve peaks over six hundred metres in height. Slieve Donard, Northern Ireland’s highest mountain, is the tallest at 850m. To the north the Slieve Croob Massif rises to a height of 534m.

While granite mountains dominate the Mournes, much of the area, like most of Co. Down, is underlain by Silurian rocks – shales, mudstones or greywackes.  These formed over 420 million years ago, from mud, sands and silts lying at the bottom of an ocean known as the Iapetus Sea. When this ocean spread, Scotland and Northern Ireland were separated from England, Wales and Southern Ireland. The world really did look very different then – unrecognisable from what we have today. 

The high Mournes granites developed a mere 56 million years ago, 10 million years after the dinosaurs had become extinct. During this time there was a huge amount of volcanic activity. The result was the great continents moving apart, leaving what is now the North East Atlantic Ocean. This was also the time when other famous geological features formed in Northern Ireland, including the Giants Causeway and the Ring of Gullion.

Newry’s Granodiorite complex, however, is much older than the high Mourne granites. This complex crystallised in the Caledonian period – about 400 million years ago – when the ancient lapetus Ocean closed. These granites are seen in the summits of Slieve Croob, Slievenisky and much of the hilly landscape north and west of Castlewellan.

The mountains formed out of molten magma, but they were not volcanoes. The rock came from the earth’s centre but never quite broke through the Earth’s surface as lava. It bubbled up inside the Earth’s crust. It then slowly cooled beneath the overlying sandstone into the interlocking crystals of quartz, feldspar and mica that form granite. The granite mass that is now exposed was formed when blocks of Silurian shale subsided, leaving a cavity which was filled by an up welling of acid magma.

Once formed, however, it took millions of years and at least six ice ages to reveal the Mourne mountains. The Silurian rocks probably formed a complete ‘roof’ over the granite intrusions – but over millennia the softer rock was gradually eroded away by weather. Only a tongue of Silurian rock remains of that ancient ‘roof’. This is located in the heart of the high Mournes, at the Deer’s meadow, at Spelga reservoir.

Once the underlying hard granite revealed itself to the elements, the great ice sheets further carved and shaped this robust rock into the enduring domed peaks we see today. Intense glacial erosion created steep sided U-shaped valleys, hanging valleys, and other features such as corries and valley moraines. During later glaciations, massive ice sheets moved from Scotland or the north and west of Ireland. These were deflected around the mountains creating the ‘fjord’ of Carlingford Lough, and the adjacent Mourne plain complex.

“The way of life of a people, including their attitudes, values, beliefs, arts, sciences, modes of perception, and habits of thought and activity”.

The Mourne landscape has shaped the way of life and vice versa. This was truly appreciated by the renowned geographer, Estyn Evan. He believed that the intertwining of habitat, heritage and history provided the geographical basis for regional identity and the sense of place. In 1951 Evans published his book ‘Mourne Country’, saying ‘..stories cling to almost every species of tree and plant’. It could also be said that stories cling to every stone and the many structures made from stone !

Mourne is not just about scenery, habitats and wildlife – it has been a ‘living landscape’ dating back for many generations. It’s a dynamic and ever changing landscape. Man’s interaction with nature and stone can be seen in ancient pre-Christian and Christian sites. It’s also evident in the scheduled monuments – from dolmens to castles – and in the remnants of traditional farming practices eg lazy beds and booley huts.

Access to the coast means that fishing has always been important. However, it also meant that Mourne granite could be easily exported, giving rise to a rich industrial heritage. The skills of the Mourne people were used in building the dry stone walls and the Mourne Wall. The latter is a gravity-defying wall that weaves its way for 22 miles over the highest summits. It is matched in beauty and engineering prowess by the majestic Silent Valley and Ben Crom reservoirs, supplying Belfast’s water needs since the1930s.

Glacial deposits of sand and gravel, particularly around the Mourne Plain, support sand and gravel extraction. And of course around all of this industry are layers of social history, cultural traditions and folklore. Find out more about culture and history here.

The importance of the Mourne AONBs habitats and the resulting biodiversity is indicated by the presence of multiple national and international conservation designations.

A particular jewel is Carlingford Lough, which supports significant numbers of sandwich terns. Its mud flats support light-bellied brent geese and large numbers of waders such as oystercatcher and ringed plover. For this reason it is designated as an international Ramsar Site and European Special Protection Area for birds.

Inland, the high Mournes are important for their purple heather and the other species that make up one of Europe’s finest tracts of upland heath. Murlough’s dune grassland and lowland heaths support one of the largest populations of marsh fritillary butterfly in Northern Ireland. While Rostrevor’s ancient oak wood nurtures a rich and diverse understorey of hazel, holly and ground flora including toothwort and bird’s nest orchid. These sites are European Special Areas of Conservation. Rostrevor Wood and Murlough are also designated as National Nature Reserves.

For more information on Murlough NNR – https://www.nationaltrust.org.uk/visit/northern-ireland/murlough-national-nature-reserve

The scrubland of Ballybannon Fen supports a variety of sedges, rushes and mosses, as well as common butterwort. The nutrient poor waters of Castlewellan Lake encourage the rare quillwort and, in the shallows, shoreweed grows. Otter footprints can also be found. These are Areas of Special Scientific Interest, designated by the United Kingdom.

The Shimna and Trassey rivers and the Slieve Croob Massif are protected under local planning regulations as Sites of Local Nature Conservation Importance. Other sites are also being considered for designation as Local Nature Reserves.

All Mourne habitats and wildlife are special, so please explore and enjoy responsibly.

To view all of the protected areas in Co Down – https://www.daera-ni.gov.uk/protected-areas/county/dn

The Mourne AONB is designated for the qualities of its landscape.  That landscape contains a remarkable range of natural and semi-natural habitats – a delightful mosaic of heather, moor, bog and pasture, dotted with freshwater and woodlands. Coastal areas boast sandy and rocky shores with mudflats as well as salt marsh.

Unsurprisingly, upland habitats – including upland and montane heath and blanket bog – are particularly important. The lowland countryside is dominated by agricultural land but also has important semi-natural habitats including hedgerows, lowland heath, dry acid grassland and meadows. Woodlands cover only about one fifth of the Mourne AONB. Over half of this is conifer but containing some broadleaved woodlands as well. More than 340 km of rivers and streams criss-cross the area. Some of these waterways feed major reservoirs, others support Otter populations and provide excellent spawning grounds for Salmon and Trout. Wetlands, including marshes and fens, provide the perfect habitat for dragonflies and damselflies.

And then there’s also the Mourne coast, bathed by warm waters from the south Irish Sea. An important nursery area for young fish, its saltmarsh and mudflats also support large numbers of wintering waders. Off the coast, the cold northerly waters of the North Atlantic meet warmer waters from the south, resulting in an unusual mixing of species ranging from microscopic algae (phytoplankton) to grazing animals. Mammals, including Common and Grey Seals as well as Dolphins and Harbour Porpoise, can all be found. Sea birds, such as the Common and Sandwich Tern, use the open sea as a feeding ground.