Loch Ness Geology

The Great Glen is a rift valley dividing the Grampian Mountains from the Northwest Highlands. The Great Glen Geologic Fault extends from the coastline of The Black Isle to Loch Linnhe. The Fault is about 700 million years’ old. As the Fault is very straight and long, the sky and water appear to join when you watch from the shore at Fort Augustus on a clear day.

Earthquakes & Ice

There were 56 earthquakes near the Great Glen Geologic Fault between 1768 and 1906 and there was a big tremor in Inverness in 1934. Loch Ness is about 10,000 years old and was formed at the end of the last Great Ice Age during which The Great Glen had been filled by a huge glacier.

Water & What's in it?

Loch Ness is the most famous Loch in The Great Glen, possibly in the world. The others are Lochs Dochfour, Oich, Lochy and Linnhe. The Loch’s surface is 52 feet above sea level and, at 21.8 square miles, Loch Ness is the second largest Scottish Loch by surface area after Loch Lomond.

The building of the Caledonian Canal during 1803 – 1822 raised the level of Loch Ness by 6 feet. Loch Ness is 23 miles long, a mile wide at its widest point and an average of 600 feet deep. Its deepest point was long thought to be 754 feet, until a new maximum depth of 786 feet was recorded in 1992. There is a layer of sediment at the bottom of the Loch, up to 25 metres in depth, and below that a layer of clay, of unknown thickness, before the bedrock is reached. Loch Morar is the only deeper Loch in Scotland at 1017 feet.

Cherry Island near Fort Augustus is the only “island” on Loch Ness and is really a man-made Iron Age Crannog. The River Ness is the only river that flows out of Loch Ness and is one of the best rivers in which to fish in Scotland. Salmon, trout and other fish can be found in Loch Ness. The water in Loch Ness averages 42 degrees Fahrenheit in temperature and never freezes however hard the winter. The water appears very black and you can only see through the top 5 feet of the Loch due to the peat lower down where “Nessie” is reputed to hide!

More detailed information about the “Geology of Glen Mor and the area around Loch Ness” can be obtained at HERE