Chapter xli

. The magnificent precipices of Faroe, which in Myling Head reach a height of 2260 feet, present a series of natural sections altogether without a rival in the rest of Europe. They are less concealed with verdure than those of Mull and Skye, and therefore display their geological details with even greater clearness than can be found either in Scotland or in Ireland. I would especially refer to the bare precipitous sides of the long narrow islands of Kalsö and Kunö, as admirable sections wherein the characters of the plateau-basalts are revealed as in a series of gigantic diagrams. The scarcity of vegetation, and the steepness of the declivities which prevents the abundant accumulation of screes of detritus, enable the observer to trace individual beds of basalt with the eye for several miles. Thus on the west side of Kunö, one conspicuous dark sheet in the lower part of the section can be followed from opposite Mygledahl in Kalsö to the southern end of the island. There is one concealed space at the mouth of the corrie behind Kunö village, but the same, or at least a similar band of rock at the same level, emerges from the detritus on the further side, and may possibly run into the opposite promontory of Bodö. It extends in Kunö for at least six geographical miles.

[Illustration: Fig. 288.--Dying out of Lava-beds, east side of Sandö, Faroe Isles.]

These vast escarpments of naked rock show, with even greater clearness than the precipices of the Inner Hebrides, how frequently the basalts die out, now in one direction now in another. The two sides of the Kalsöfjord exhibit many examples of this structure, and some striking instances of it are to be seen on the west side of Haraldsfjord. In these cliffs, which must be about 2000 feet high, upwards of forty distinct flows can sometimes be traced from the sea-level to the crest. The average thickness of each bed is thus somewhat less than 50 feet. Such vast escarpments, with wide semicircular corries scooped out of their sides, such serrated crests and dark rifts in the precipices, such deep fjords winding through nearly horizontal basalts, of which the parallel sheets can be followed by the eye from island to island, fill the mind with a vivid conception at once of the enormous scale of the volcanic eruptions and of the stupendous denudation which this portion of North-Western Europe has undergone since Tertiary time.

As the lenticular character of the basalts, and the evidence they supply of having been discharged from many small local vents are of great importance in the comprehension of the volcanic history of the plateaux, some further illustrations of these features may with advantage be given here. Thus the traveller who skirts the western precipices of Suderö will notice some good examples to the north of the highest part of the cliffs. On Stromö he will detect other cases of the same structure. Similar features will arrest his attention on the precipices of Sandö, where, though at first sight the basalts seem to be regular and continuous, a nearer view of them reveals such sections as that shown in Fig. 288, where a group of sheets rapidly dies out towards the north against a thicker band that thins away in the opposite direction. Further north he will come upon other examples in the range of low cliffs between Kirkebonaes and Thorshaven, and more impressive still in the rugged precipices that front the Atlantic on the western front of Hestö (Fig. 289), where the disappearance is in a northerly direction.

[Illustration: Fig. 289.--Lenticular lavas, western front of Hestö, Faroe Isles.]

But it is in the northern part of the Faroes, where the basalt-plateau has been so deeply trenched by parallel fjords as to be broken up into a group of long, narrow, lofty, and precipitous insular ridges, that the really local and non-persistent character of the lavas can best be seen. The eastern cliffs of Svinö present admirable examples, where in the same vertical wall of rock some of the basalts die out to the south, others to the north, while occasionally a shorter sheet may be seen to disappear in both directions as if it were the end of a stream that flowed at right angles to the others (Fig. 290).

[Illustration: Fig. 290.--Lenticular lavas east side of Svinö, Faroe Isles.]

The more the basalt-plateaux of Britain and the Faroe Islands are studied, the more certain does the conclusion become that these widespread sheets of lava never flowed from a few large central volcanoes of the type of Etna or Vesuvius, but were emitted from innumerable minor vents or from open fissures. In a later chapter an account will be given of the vents, which may still be seen under the overlying sheets of basalt, and, in particular, a remarkable group in the Faroe Islands will be described.

[Illustration: Fig. 291.--Section at Frodbonyp, Suderö, Faroe.]

The occurrence of tuffs, leaf-beds and thin coals between the plateau-basalts of the Faroe Islands has long been known. These stratified deposits are well seen in the island of Suderö, where they serve to divide two distinct series of basalts, like the iron-ore and its accompaniments in Antrim. As a characteristic illustration of the same diversity of deposits observable between the lava-sheets of the basalt-plateaux of the British Isles I give here a section exposed on the east side of this island--a locality often visited and described in connexion with its coal-seams (Fig. 291). At the base lies a sheet of basalt (_a_) with an irregularly lumpy upper surface. It may be remarked that the lower group of basalts is marked by the occurrence of numerous columnar sheets, some of them possibly sills, and also more massive, solid, and durable basalts than the sheets above. The lowest of the intercalated sediments are light-coloured clays, passing down into dark nodular mudstone and dark shale, the whole having a thickness of at least 20 feet (_b_). These strata are succeeded by (_c_) pale clays with black plant-remains, about three feet thick. Immediately above this band comes the coal or coaly layer (_d_), here about six inches thick, which improves in thickness and quality further inland, where it has been occasionally worked for economic purposes. A deposit of green and brown volcanic mudstone (_e_), twelve feet in thickness, overlies the coal and passes under a well-bedded granular green tuff and mudstone three feet thick (_f_). The uppermost band is another volcanic mudstone (_g_) four feet in thickness, dark green in colour, and more or less distinctly stratified, with irregular concretions, and also pieces of wood. Above this layer comes another thick overlying group of basalts (_h_) distinguished by their abundantly amygdaloidal character, and by their weathering into globular forms which at a little distance give them a resemblance to agglomerates.

We have here an intercalated group of strata upwards of 40 feet thick, consisting partly of tuffs and partly of fine clays, which may either have been derived from volcanic explosions or from the atmospheric disintegration of basaltic lavas. Through some of these strata abundant carbonaceous streaks and other traces of plants are distributed, while among them lies a band almost wholly composed of compressed vegetation. Unfortunately none of the strata at this locality seem to have preserved the plant-remains with sufficient definiteness for identification. There can be no doubt, however, that they were terrestrial forms like those of Mull and Antrim.

This coal, with its accompanying sedimentary deposits, has been traced through Suderö, and another outcrop, possibly of the same horizon, occurs on Myggenaes, the extreme western member of the group of islands, at a distance of some 40 miles.[266]

[Footnote 266: See in particular Prof. J. Geikie, _Trans. Roy. Soc. Edin._ vol. xxx. (1880), p. 229.]

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