The Sandfell Laccolith and ‘Dome of Elevation’

. Introduction The eastern part of Iceland is built mainly of a great series of plateau basalts dipping at low angles to the west, and the structure is magnificently exhibited in the sides of the deep valleys and fjords which incise the 3000–4000-foot plateau. The traveller is impressed by the constancy of the almost flat-lying trap featuring, which persists in the region of the ‘stock’ intrusions to the south (Cargill et alii , 1928), so that Sandfell, a hill of light-coloured rock on the south side of Faskrudsfjord, at once attracts attention because the basalts are disposed at high angles in proximity to it—a circumstance which was noted by Thoroddsen (1906, pp. 268, 277). The hill is a splendid example of a laccolith similar in type to those of the Henry Mountains, Utah, and equally impressive in its exposure. The combination of conditions which made the intrusions of the Henry Mountains the type of their class is present here—approximately level strata, intense erosion, and absence of vegetation (Gilbert, 1877, p. 97). The main hindrance to the complete elucidation of the structure is the extensive screes—to which Sandfell owes its name. This paper is based upon field investigations made on four visits between 1914 and 1932. In the earlier stages of the work snow-drifts hid some of the higher parts, but there has been a marked amelioration of climate in latter years, and in August 1932 all the drifts had disappeared. The district is unmapped, and in 1928 the second author made