Southwards from Killin
Glen Ogle
The crags of Glen Ogle not only add to the atmosphere of this area but are a result of the turmoil, millions of years ago, that placed the extremely old limestone sediments on top of far younger layers.
Although a glacial arm broke through the Glen 10,000 years ago, water is still a feature that forms new scars on the landscape. You will notice that near to the old railway viaduct there is a large rockfall caused by water freezing and expanding in rock cracks. This eventually causes rock to break from the crag face. One such fall contributed to the early closure of the railway.
Lochearnhead and St. Fillans
Loch Earn is typical of the northern glens of the National Park in that it is very narrow and long. As the ice sheet moved eastwards from Lochearnhead, it would be trying to carve its way through cracks in the hard Dalradian rocks and this squeezed the glacier high and thin – giving rise to a narrow but deep loch system. Beyond where present day St. Fillans is, the ice would have met with the soft sandstone rocks of the Strathearn fault line and the glacier would have cut its way through these soft rocks like a knife through butter. This allowed it to spread and therefore the valley broadens and is relatively shallow.
Balquhidder - Kirkton Glen
At the top of the Glen, before it drops into Glen Dochart, you can clearly see the igneous outcrops and crags that were formed through the volcanic super-heating of magma. You can also see some of the infrequent and unusual high limestone crag exposures that give rise to rarer plants.
Balquhidder to Strathyre
The River Balvaig that flows from Balquhidder to Strathyre and into Loch Lubnaig was around before the last ice age (more than 14,000 years ago) and it is thought that, originally, it streamed past where Kingshouse and Lochearnhead now are and flowed into Loch Earn.