The remains of ancient craters can be distinguished, but their outlines have been greatly destroyed by denudation.
Where a rock yields to weather with considerable uniformity in all directions it is likely to assume conical forms in the progress of denudation.
That the volcanic period was a prolonged one is shown by the great denudation of the plateaus before the last eruptions took place.
Denudation has continued active ever since, and now, owing to greater hardness and consequent power of resistance, the glassy lava stands up as the prominent and picturesque ridge of the Scuir, while the basalts which formerly rose high above it have been worn down into terraced declivities that slope away from it to the sea.
It lies in a basin among granite hills, nowhere exceeding 2627 ft., remarkable for their denudation and their abrupt black crags and pinnacles.