A Highland nature reserve whose geology has contributed much to our understanding of the earth's history has reopened.

TV geologist Professor Iain Stewart, star of BBC Two's Men of Rock, was at the Knockan Crag 13 miles north of Ullapool which attracts more than 10,000 visitors a year.

New panels, audio and touch-screen displays in Gaelic and English explain the role played by Victorian geologists Ben Peach and John Horne in interpretation of the planet's mammoth geological movements.

Knockan Crag has a unique cliff-face that at one point appeared to rock the very foundations of Darwin's theory of evolution.

Darwin owed deep gratitude to Scottish pioneer geologist James Hutton, who had clearly shown through fossils how life evolved over millions of years from the lower, older rock layers to the newer ones nearer the surface.

But part of Knockan Crag looked to turn this theory on its head when it was discovered at the end of the 19th century the natural form is upside down, with its oldest rocks at the top and the newest ones at the bottom.

It emerged this strange feature, which provoked furious debate among geologists, was the result of collisions of land masses 400 million years ago. These gave rise to an event known to geologists as the Moine Thrust.

This pushed a deep crust of rock up and over sedimentary layers of more recently formed sandstone and limestone. White quartzite is on the top layer of many hills in the area, making them look snow-capped all year round.

Stewart was Scottish Natural Heritage's guest of honour at the launch of the new facilities yesterday after a two-year revamp. His TV and radio work includes Walking Through Landscapes for BBC Radio Scotland; Making Scotland's Landscape; and How to Grow a Planet for the BBC.

He said yesterday: "This place in the north-west of Scotland is of global importance and is one of the oldest landscapes in Europe. The rocks tell of ancient oceans, vast deserts and ice sheets. At Knockan Crag you can get a glimpse of the complexities of geology and strength of Earth movements by examining the rocks."