page_title: Glen Roy
section_title: Historic geological investigations
hierarchical_section_title: Glen Roy / Historic geological investigations
caption_attribution_description: English: Glen Roy &amp; parallel roads
context_page_description: Glen Roy in the Lochaber area of the Highlands of Scotland is a glen or valley much of which is designated as a national nature reserve noted for the geological phenomenon of the three 'roads'.
  The "Parallel Roads" of Glen Roy are loch terraces that formed along the shorelines of an ancient ice-dammed loch. The loch existed during a brief period of climatic deterioration, during a much longer period of deglaciation, subsequent to the last main ice age. From a distance they resemble man-made roads running along the side of the Glen, hence the name.
  The glen runs north from Glen Spean which takes the main A86 trunk road and the railway of the West Highland Line, both running about a further 23 kilometres southwest via Spean Bridge to Fort William. The village of Roybridge and Roy Bridge railway station are sited where the River Roy joins the River Spean, and from there a narrow single track road runs north up the glen for almost 16 kilometres to Brae Roy Lodge.
context_section_description: In the 19th century, the Parallel Roads attracted the attention of many early geologists, including the Reverend William Buckland, Charles Lyell, James Nicol,  Charles Babbage, James Geikie, and Joseph Prestwich. This interest ensured that the Parallel Roads featured prominently in the development of geological science.
  Charles Darwin visited the glen in June 1838 and, drawing on his recent findings in South America during the Beagle expedition concluded that the shorelines were raised beaches of marine origin. His paper on the subject was published in 1839 in the Philosophical Transactions of the Royal Society. This was contradicted in 1840 by Louis Agassiz's Glacial theory which postulated that the Glen Roy shorelines had been cut by freeze-thaw processes of loch ice during the maximum extent of glacial ice in the climatic reversal known as the Younger Dryas / Greenland Stadial, or locally the Loch Lomond Readvance. Darwin defended his paper over many years. 
  In 1861 Thomas Jamieson was advised by Lyell and Darwin about visiting the Glen, and given memoranda and maps by Darwin. After visiting the glen a second time in the summer of 1862, Jamieson wrote to Lyell on 15 August reporting his findings. On 6 September Darwin told Lyell and Jamieson that he was convinced: "My paper is one long gigantic blunder". Jamieson's paper on his investigations was published in 1863. Four decades after Darwin's 1839 paper and shortly before his death, in a letter to Joseph Prestwich, he said that he gave up his Glen Roy theory when he read T. F. Jamieson's (1863) paper but he agreed with Prestwich's criticism of Jamieson's interpretation of the Glen Turret delta.
  Interest in the Parallel Roads continues to this day, both among earth scientists intrigued by the dramatic processes that shaped that landscape, and among tourists attracted by the natural wonder of the landforms.
caption: A viewpoint on the single track road, looking north up the glen.
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