Some observations on the Long Row and the Dasses, Arthur's Seat

Abstract

The conspicuous escarpment among the volcanic series of Arthur's Seat, known as the Long Row or Well Crag, has afforded considerable speculation as to its true origin. There is a continuation of this same rock on the other side of what is now known as the vent of the comparatively small volcano that existed in very early Carboniferous times at this place. The relationship of the Long Row and of its prolongation, the Loch Craig, to the volcanic vent seem to prove beyond doubt that they were once continuous but were broken through at the spot where the vent occurs. There is, underlying the Long Row and the Loch Craig, a series of intrusive igneous rocks known as the Dasses, where they appear exposed above Hunter's Bog, and as Girnal Craig, where they appear immediately below the Loch Craig by Duddingston Loch. This series of intrusive rocks has also generally been regarded as having been blown through by the volcano, thus giving them an existence previous to that of the volcano itself. The “Memoir of the Geological Survey of the Edinburgh District” has a note upon this point, p. 72:— “Although the Basalt sill of Girnal Crag, as shown on the map, appears as if truncated by the edge of the vent, the section is obscure at this point, and it is by no means certain that such is actually the case. In fact the resemblance of the basalt of the Dasses to the intrusive rocks of the Lion's Haunch,