The escarpments on the east side are cut by three or four glens. The largest one, about half-way down the coast, gives access to the interior.
The most striking feature, looking up the glen, is the great stock of an acid intrusive rock, which rises to 2,270 feet. It can best be described in the words of Scott:
“Shooting abruptly from the dell
Its thunder splintered pinnacle.”
Geology
The island is the result of a series of fissure flows of a basaltic and trachytic nature. These flows have been intruded by the stock just mentioned above, and many fissures were opened by it. These have subsequently been filled by dykes. The rock forming the dykes is very hard, with the result that they are now a very prominent feature, and stand up in some cases about 50 feet above the surrounding country. This is due, of course, to differential weathering.
It is probable that the east coast represents a fault plane, but as the erosion has been great, direct evidence is wanting. Apart from this fault no faulting nor folding was observed.
Photo: Wilkins