In the nineteenth century, the prominent natural feature that is shown here was known locally as the Gates of Sodom. Here, a geological dyke, a wall-like intrusion of igneous rock, cuts across NS4178 : Auchenreoch Glen
, whose sides otherwise consist of deposits of sedimentary rock (see NS4178 : Ballagan Beds in Auchenreoch Glen
). The sides of the Gates are ten metres or more high.
Auchenreoch Glen is the valley of a large tributary of the Murroch Burn; the dyke traverses the deepest part of the glen, close to the junction of the two burns.
The section shown in the photograph is just part of a much longer dyke, which extends for hundreds of metres. It is just one of several parallel dykes (oriented SW-NE) that cross Auchenreoch Muir. Their course can easily be followed on satellite imagery, but, on the ground, they are most apparent at the places where they cross the numerous stream valleys; see, for example, NS4278 : Stream valley
. However, the Gates of Sodom provide the most impressive example.
"Annals of the Andersonian Naturalists' Society" (Volume 3), published in 1908, includes a section headed "Records of Excursions in Dumbartonshire". One of these excursions took place on Saturday, 10th September, 1892; the record of that outing notes that "at a point a little over a mile above Murroch Farm the main stream is joined by a tributary coming from the eastward, the bed of which is cut across, near its junction with the Murroch Burn, by a trap dyke of considerable thickness, through which the water has cut a rather curious opening known as the 'Gate of Sodom'."
An earlier usage of the name occurs in the May 1862 edition of the magazine "The Geologist"; that issue reports a similar excursion on Friday the 11th of April, 1862, by the Glasgow Geological Society. There, the feature is described as "the 'Gates of Sodom', a vertical dyke of greenstone-porphyry crossing the course of the stream, which flows through a breach in this natural barrier".
For other views, see NS4178 : The Gates of Sodom
and NS4178 : The Gates of Sodom
Not far upstream, there is another prominent feature, whose name carries on the same theme: NS4178 : Lot's Wife