THE characteristic landscape of some of the most breathtaking scenery in Scotland really is older than the hills.
New research has revealed that the deep glens and spectacular corries of the Cairngorm mountains were formed millions of years earlier than previously thought.
The landscape has the appearance of a typically glaciated landscape formed during the Ice Age in the past 2.5 million years.
However, geologists revealed yesterday that the creation of many of the famous straths and glens, such as the Lairig Ghru, Gleann Einich and Glen Avon were initiated, through weathering and erosion, 390-400 million years ago.
The research, which was jointly funded by the British Geological Survey (BGS) and Scottish Natural Heritage (SNH), found that zones of weakened rock were formed from hot f luids, which circulated around cooling granite while it was still buried underground.
When the Cairngorm granite became exposed to the surface 390-400 million years ago, rivers and erosion led to the formation of valleys that make up contemporary straths and glens.
John Gordon, earth science group manager at SNH, said of the mountain ranges which are among the oldest in Europe and North America: "Geologists have thought for some time that the Cairngorms is an example of a very old granite landscape, but this is the first time we can actually trace its lineage back to the time of formation of the granite.
"The major glens have been shown to follow the lines of weakness in the granite and these originated when the granite was cooling. There were still fluids circulating within the semi-cooled rock and these weakened the existing fractures further and chemically altered the adjacent rock.
"When the granite was later exposed at the surface, weathering and erosion attacked these weaker rocks and early rivers started to form the landscape. This research offers a unique insight into the landscape history of Scotland over the past 400 million years."
Chris Thomas, a principal geologist at BGS and Cairngorm project team leader, said:
"The Cairngorm granite was formed by magma cooling in the earth's crust around 427 million years ago."
The study, Geological Structure and Landscape of the Cairngorm Mountains, involved geologists examining the composition and structure of granite at about 700 sites within the Cairngorms.
They examined the composition and structure of the granite to look for clues about the history of the rock and found that the lines of weakness which had been exploited by streams and other agents of weathering and erosion, corresponded to the original fracture lines formed when the rock cooled.
They then reconstructed the landscape before the Ice Age and showed that the glaciers had been extremely selective with the land they modified.
For example, An Garbh Choire, a corrie between the Munros of Braeriach and Cairn Toul, was carved out by glaciers to a depth of 500 metres, compared with just a few metres on adjacent plateaux.
They also discovered that conspicuous rock pillars or tors found on certain mountains such as Ben Avon, Bynack More and Beinn Mheadhoin dated back to a time of a warmer, wetter climate, just before the Ice Age. This was when weakened granite broke down rapidly, and left the tors upstanding.
ROCKS OF AGES
The formation of other mountains:
Himalayas formed 25 to 70 million years ago.
Alps formed five to 38 million years ago.
Andes formed two to 143 million years ago.
Pyrenees formed two to 65 million years ago.
Appalachians formed 440 to 480 million years ago.
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