Landscape in the North-West Highlands of Scotland
Ben Peach & John Horne
Sometimes, two scientists work so closely together and complement each other so well that
their names become inseparable. So it is with Peach and Horne, names that are legendary in the
context of the mapping of the North-West Highlands of Scotland and the gathering of evidence
for thrust tectonics. Their 1907 memoir and associated mapping of the region set a standard that
is still considered exemplary today. Generations of geologists have travelled to their study area
to follow in their footsteps and train in the mapping of structural complexity, in the hope that
they can emulate Peach and Horne’s work, which, in the words of the great Austrian geologist,
Edward Suess, “rendered the mountains transparent.”
The North-West Highlands remains one of the few wilderness areas in Britain, famous for
spectacular scenery where isolated mountains rise out of peat bog. To geologists, the region is
equally famous for its spectacular geology, involving some of the oldest rocks on the planet in a
stretch of outcrops 200 km long and 25 km wide.
In the second half of the 19th century a controversy had developed concerning the stratigraphy
and structure of the region. The basic rock units present had been known since the early
1800s. In apparent stratigraphic order (lowest first) there are: a deformed set of gneiss and
other metamorphic rocks (now termed the Lewisian Complex); a series of reddish sandstones
(Torridonian Sandstone); white quartzites and limestones (now known to be Cambrian and
Ordovician); and a thick series of metamorphosed sediments (the Moine Schists).