The Highland Line
The sharp change in topography, weather, vegetation, and wildlife, marked by the Highland Line, from Helensburgh via Balmaha, Aberfoyle and Callander and continuing northwards to Stonehaven, is reflected in the culture and population density. The Line has played an important role in the colourful history of Scotland, dividing the Highland Clans from their wealthier Lowland neighbours. It is no surprise that disparities in the fertility of agricultural land, the climate and the living conditions historically resulted in regular raids from Highlanders on their southern neighbours.
The Highland-Lowland boundary reflects the major geological change from hard Dalradian metamorphic rocks in the north west to pebbly conglomerates and softer sandstones of Devonian age immediately to the south east. Between the two there is a sequence of lavas, conglomerates, limestones, black mudstones and sandstones which are different to both Highland and Lowland rocks, called the Highland Border Complex. They form a zone up to 1.2 kilometres wide which is found between Balmaha and Callander. These rocks came from both deep and shallow waters and once formed part of the floor of a small ocean basin. We know this because of the marine fossils found in the limestones, although these are very small and difficult to find. The rocks range in age from about 550 million to 445 million years old. They became attached to the Highland block by lateral faulting as a result of plate tectonic movements.
Highland Border Complex rocks form hilly ground, which near Callander lies between the higher ridges of the Menteith Hills and Callander Craig to the southeast, and the rocky crags of the Dalradian which overlook them to the northwest.
Immediately southeast of the Highland Boundary Fault at Balmaha Pier, pebbles in the Devonian conglomerates have open vertical cracks which show that the rocks were stretched as lateral movements occurred between the two blocks separated by the fault. We know that these movements happened about 420 to 390 million years ago.
Much of the above geology can be seen on the Highland Boundary Fault trail at David Marshall Lodge near Aberfoyle.
The Trossachs, literally translated from the Gaelic as ‘bristled territory’, is strictly defined as the narrow rocky, wooded valley between Loch Achray and Loch Katrine, but it is now used for the wider area between Callander, Loch Katrine and Aberfoyle. It lies mainly within the Highlands and the complex pattern of the underlying geology is partly reflected in the landscape.
In the 17th to 19th centuries trade in cattle reared in the Northwest Highlands was important, and drove routes were established to the fairs or ‘trysts’, at Crieff and later at Falkirk. One of the major routes led via Tyndrum to Crainlarich, Glen Gyle and Loch Katrine. It crossed volcanic ‘Green Beds’ on the north shoulder of Ben Venue via Bealach nam Bo (Pass of the cattle). This particularly steep part of the route attests to the nimbler cattle of former times.
The accessible but wild beauty of the Trossachs was first publicised by the Reverend Dr Robertson who reported on the parish of Callander in 1768. He described the Loch Achray – Loch Katrine valley as ‘a tumultuous confusion of little rocky eminences, all of the most fantastic and extraordinary forms, everywhere shagged by trees and shrubs’.
In the following 50 years, several well-known writers, including Wordsworth, Coleridge and Walter Scott, visited the Trossachs. It was Scott, in the poem Lady of the Lake (1810), who encapsulated the romantic wildness of the area in the style favoured at the time. This led to a great increase in the numbers of tourists visiting the area in the 19th century. The use of Loch Katrine for Glasgow’s water supply and the adjacent hills for coniferous forestry have tamed parts of the area, but the oak woods, glaciated rocky eminences and backcloth of ice-moulded craggy hills still remain.