The commanding position, the imposing dimensions, the remarkable preservation of the Nimrud crater cannot fail to arouse the curiosity of the traveller, as he sees it from afar or passes it by. In summer it is a circle of grassy cliffs with a vaulted outline; during winter and autumn, when the higher levels are early robed in snow, it is a startling presence against the sky (see [Fig. 145], p. 142). From any point you command but a small portion of the vast circumference, which, measured upon our plan, amounts to 14½ miles. Of unequal height, the edge of the basin is most elevated upon the north, where at two points it attains an altitude of nearly 10,000 feet. It is lowest upon the east and west; in either quarter the outline dips to a level of 8100 feet. But the circle is nowhere broken; the rim of the caldron remains intact, although worn down and, in places, chipped. With two great depressions on either side, the lake of Van (5600 feet) and the plain of Mush (4200 feet), such a presence fills the landscape and engrosses the eye.
Nor is the imagination disappointed when the interior of the crater is seen for the first time. I have already described the impression which that view produced upon us, entering it from the east. The lake fills almost the whole of the western half of its area, at a level of 7656 feet. The remaining portion consists of older lava streams, covered with pumice, and of some more recent, which bristle with sharp crags. The eastern shore of the lake is deeply indented, and the volcanic matter has cooled in the form of high banks. The figure described by the walls of the crater is almost exactly circular, the diameter being greatest along an east-north-east line, or between the fork, where we first entered the basin, and the passage in on the west (c and m on plan). The distance between these points is nearly 5 miles (8500 yards). Nimrud is therefore one of the largest perfect craters in the world.[2] The period during which it seethed with a lake of molten matter, which overflowed into the lower levels on every side, must date far beyond the limits of history. At the present day not a wreath of smoke ascends from the volcano; though at times a little landslip sends the fine sand into the air, with much the same appearance as a cloud.
But the student of volcanic phenomena could not select a better example of the successive stages of eruptive activity. In an earlier stage we must suppose the walls of the crater somewhat higher, and the area considerably narrower which they enclosed. The earliest lavas, in the case of Nimrud, were of an acid and viscous description (rhyolitic augite-andesites); and, as often as they rose above the lip of the caldron, they did not flow very far. But the later basaltic lavas had a larger extension; and to them is due, in no small measure, the plateau on the east of Tadvan, which acts as a dam to the lake of Van. The molten lava surged against the precipices which confined it, and gradually wore them back. The work of enlargement was advanced by violent explosions, which were principally directed against the western and eastern sides of the volcanic basin. The uppermost and steepest portions of the wall were, on these two sides, completely blown away. This epoch in the life of the volcano, the storm and stress of a tumultuous youth, was followed by the gradual subsidence of its energies. The streams of lava were confined to the interior of the crater, and the deeper portion came to be covered with a lake. It was perhaps at this period that were produced the little craters which figure on the outer slopes of the principal caldron, roughly along meridional lines. Such minor points of emission were also formed within that caldron, and from them proceeded some of the older flows which cover its floor. Explosions again occurred; but their effects were only local. They blew away portions of the little craters, and sent up showers of dust, which, falling to the ground, cloaked the surface of the lava streams. The latest and moribund stage is represented by those bosses of lava which form such a conspicuous feature. The viscous matter welled up along old lines of weakness, and from the chimneys of the little craters. One of these bosses divides a small warm lake from the main sheet of water; others form little peninsulas in the principal lake (C, D, E). They have all the appearance of being fairly recent, and they are not yet overgrown with wood. Finally one may mention some extensive flows of cinder, about the base of the little crater on the outside of the mountain, on the north of the circle of cliffs. They might have issued a few months ago.
To these various manifestations of the expiring forces of the volcano is due the present weird and troubled aspect of the interior, which formed the basis of our first impression. The little wood is confined to the neighbourhood of the lake; the remaining portion is barren and rugged. A high hill, covered with pumice, and about in the centre of this region, affords an admirable standpoint from which to survey the whole (L on plan). The little lakes which figure on the plan are due to the melting snows. I doubt whether you would find a spring of good, fresh water; we all drank the water of the lake. The warm lake is situated beneath the escarpment of the wall on the north, and is almost contiguous with the principal sheet of water (A). Its level is about the same. But it differs from the other lagoons in respect of its colour, which, owing to the abundance of vegetation in its vicinity, is a yellow-green, resembling an English village pool. It is said to possess healing properties; but this I should be inclined to doubt. Oswald, who waded about with unflagging curiosity, hunted out the several emissions of bubbles. Their intermittent nature reminded us of similar phenomena in the shallows of Lake Van. Perhaps the gas is merely due to decaying vegetable matter upon the bottom, and the temperature principally to the powerful effect of the sun’s rays. The water in this lake, as in the big one, is rising in level, a fact which is probably due to the increased action of mineral springs. It is flat and mawkish to the taste.
I should say that it might be possible to ride round the edge of the crater within a space of seven or eight hours. But the outline is so uneven, and the ground in places so difficult, that, at the best, it would prove a very hard day’s work. We devoted considerable portions of several days to making the circuit, revisiting certain of the most important points. The ride is so remarkable, that I propose to follow it in some detail. The changing scenes which you overlook from a moderate height, from choice positions, among immediate surroundings of the grandest order, are nothing less than the geography of this part of Asia, outspread before you beyond the skill of maps.
The large feature, the leading motive of the immense landscape is the likeness, and yet the contrast, between the two great depressions on the west and east of the lofty stage upon which you stand. Both are bounded on the south by the long barrier of the Kurdish mountains; both oppose to that deep belt of serried ridges expanses of perfectly even surface. But, while the one dazzles the eye with its splendour of outline and brilliance of colouring, the other is always dim, grey, vague, and unseizable. Neither view is ever lost for very long. Even while you are in possession of the long perspective of the plain of Mush, stretching to the horizon with a wealth of subdued detail, like the nave of some great cathedral in the West, between the crags in the opposite quarter, through some fork in the outline, the blue lake, the point of a promontory, a glimpse of Sipan may still be seen.
Let us start from the point at which we entered the crater, from a level of 8150 feet (c on plan). It will be early in the morning, when the sky is flaked with cloud—beds of vapour, grey and white, scarcely concealing the field of blue, and unmoved by a breath of wind. Proceeding northwards along the wall of the crater, we rapidly ascend. Our horses’ hoofs sink in the powdery pumice sand, which is held together in places by bushes of flowering spiræa, and by tufts of grass, among which a small species of campanula hangs its pretty little violet bells. The pumice tells the story of the violent explosions to which the present aspect of the crater is due. They have enlarged the circumference of the walls of the basin; and their effect is clearly visible from the interior as one looks to the side of the wall up the edge of which we now ride. Whereas the beds of lava on the north and south walls, which are the most lofty, are seen in section as perfectly horizontal sheets, on this north-eastern wall, as well as upon the face of the corresponding cliff on the west, they have a downward slope. It is obvious that all the layers at the time of emission must have been horizontal around the original crater rim; and the pronounced obliquity of the beds on the western and eastern sides is due to their being exposed by explosive agency at a point where they had commenced to descend to the surrounding plains. The underlying lava is of the usual description, a rhyolitic andesite with a thin selvage, or upper surface, of obsidian, which shines like jet in the sun. The basaltic lavas, with their cloak of pumice, ease the gradient of the slope towards the plain in the direction of Akhlat; but the explosion has produced a steepness up which the horses are obliged to zigzag, in making north, along the edge of the cliff. A turn outwards discloses the harmony of the landscape of Lake Van; a turn inwards the mystery of the scene within the crater. The higher we rise, the more abruptly the outer slope of the wall sinks to the plains about its base. The pumice disappears; the lava gets the upper hand. After a climb of some duration, we reach the summit of the wall on the north, at a point which is almost immediately above the hot lake (b). Our elevation is now 9750 feet; and this lofty level is continued, with little intermission, for some distance towards the west.
The greatest eminence of the cliff stands back from the lip of the crater, say at an interval of 80 yards from the point described. Here, among huge blocks of reddish-brown rock, I take the boiling-point. The mean of this reading with another, registered on a subsequent day, gives a result of 9900 feet. We are therefore standing on the highest pinnacle of the whole circumference. Pinnacle and slope are free of snow; but snow would lie at this season were it not for the steepness of the slope of lava. The lava does not appear to have extended much beyond the foot of the immensely lofty crater wall. Beyond some broad-shouldered bastions, we look down into the plain south of Lake Nazik; we range the shores of that lonely lagoon. Not a tree can be discerned in that wide landscape; no strip of verdure fringes the margin of the blue water; scarcely a patch of cultivation features the plain. The block of limestone hills between us and the dome of Sipan, forming the coast of Lake Van, recess away behind Akhlat towards Lake Nazik; and, from this height, one might suppose that the level of the plain below us were continued to the borders of the inland sea. The conspicuous mountain, besides Sipan, is the rugged mass of Bilejan, rising to a sharp-edged ridge. The outlines in the north, Khamur and Bingöl, remained misty during the whole of our stay. But the delicate bedding of cloud, which may collect towards morning, soon gives way, as the day advances, to a sky of the purest blue.
West of this position, the rim of the crater flattens, although its immediate edge is much broken, apparently by earthquakes, the fissures in the surface of rock necessitating detours outward, towards the lower levels. We are approaching the little crater on the outside of Nimrud, of which mention has already been made. The wall still maintains its considerable altitude, the height of an eminence of huge boulders, by which we pass, being again 9750 feet. The little crater is situated at some distance north of the main basin, but before the ground falls away to the plain. Indeed we are now in the neighbourhood of the extensive flows of basaltic lava which are such a feature on the north-west side of the great crater. Such is the insignificance of the object for which we are making, that it might well pass unobserved from the edge of the cliff. But the curiosity is aroused by a long, low ridge, like a volcanic dike, which, commencing almost at that edge, is produced at right angles, in the direction of the plain. Realising the feature, one observes that the field of lava on the margin of the cliff is raised up into a saddle along a meridional line. A little further northwards, and at a lower level, pasty rhyolitic lavas have oozed up from long, narrow fissures along the eastern base of the ridge. At its extreme end there is a mass of the same lava; and at that point the ground breaks away towards the lower region.
Slanting off from the edge of the cliff in a north-north-westerly direction, we reach the eastern base of the low ridge. It is flanked on this side by deep fissures in the surface of the ground—gloomy chasms, partially filled with perpetual snow. Towards their upper or southernmost end there is a small circular pit, from which protrudes a boss of rhyolitic lava. A little lower down the several fissures combine, and form a long trough. This trough has been partially filled with a mass of lava, which stands up with rugged crags. From the base of this lava an extensive flow of cinders blackens the ground for a considerable distance towards north-east. The trough or principal fissure again splits up into minor cracks, as it reaches the elevated platform of the terminal crater.