The cluster of trachytic cones constituting the Tongariro group forms collectively an almost complete circle rising from a level plateau, which near the base of the mountains has a general elevation of about 3000 feet above the level of the sea. The enormous cone with its active crater, which forms the central point of the group, springs from an almost level base, and is flanked on its western and north-eastern sides by minor conical mountains, which are connected with each other by high ridges. To the north-west a series of undulating hills roll down to the plains, while to the south a steep, flat-topped spur juts out into the plateau which bounds the mountain in that direction. With the higher mountains are connected lower undulating hills, formed principally of scoria, and covered, especially towards the plains, with a luxuriant growth of native grasses, low fern, and dwarf shrubs. Right in the very centre of this great circle of cones and extinct craters, the graceful, tapering form of the burning mountain rises from the bottom of an extensive basin-like depression, which, encircled as it is by the rugged sides of the surrounding ranges, has somewhat the appearance of an ancient crater. This beautiful mountain, as it rears its tall head high above the less elevated cones, especially when viewed from its southern side, at once strikes the beholder by its wonderfully symmetrical proportions. With a slope of about thirty to thirty-five degrees, it assumes as near as possible the exact form of a sugarloaf, without a twist or a bend to mar the grand effect of its outline. To describe it, one must imagine this huge mass built up of trachytic rock, ridges of lava, scoria, volcanic conglomerates, enormous boulders, and other igneous accumulations to a height of thousands of feet, tapering off gracefully at the summit as if moulded by the hand of man. It is not a crater of elevation in the ordinary acceptation of the term, like its colossal neighbour Ruapehu, but a complete trachytic scoria cone, which may have originated from some sudden outbreak of plutonic forces, or from a small aperture in the earth's crust throwing up particles of volcanic rock similar to those of which the mountain is composed, until, through countless ages, its action becoming by degrees more extended, it gradually built itself up to its present proportions from the matter it ejected from its fiery mouth, and thus, phoenix-like, rose into being from its own ashes. When examining the great mountain, it may be plainly seen that the ridges of trachytic lava, which form, as it were, the skeleton upon which the whole structure is raised, have generally a vertical strike from the summit to the base of the cone, converging, however, gradually towards the top, and while the edges of some are inclined so as to form an almost horizontal stratum, as shown in many of the gorges, the edges of the others stand out perpendicularly, like enormous buttresses.