[Read before the Wellington Philosophical Society, 14th June, 1879.]
In the pleasant, if sometimes arduous, pursuit of art-photography, the writer camped for weeks close to the main volcanoes and geysers of the colony, enjoying excellent opportunities for search into the origin and working of these marvellous and attractive exhibitions of nature's powers. And viewing the existence, or it might be termed life, of the earth in its present state for at least thousands of years, the question naturally arose
to the wayfarer of to-day amongst these interesting scenes:—“Whence the activity which still pours forth the boiling waters of Rotomahana to run glistening down the silica terraces of their own constant formation—wherein the force that lights the red fires which burn ever in the crater of White Island—or what the motive power that still throws up a cone in the crater of Tongariro (Ngauruhoe)? “The reply from the waters of Rotomahana, from the fires of White Island, and from the cone of Tongariro was the same—the one word, “Sulphur.” Whether the almost universally imagined heat of the interior of the earth has any existence in fact does not materially affect the subject; for it was enough to the observer that sulphur in its natural state lay beneath the crust of the earth in beds of greater or less extent, being self-combustible when heated and moist, smouldering for long years—burning near the surface sufficient to melt the rocks and throw them out as lava and pumice amidst fire and smoke, and with reports like cannon—or heating the internal waters which came into contact with it, and forcing them up as minerally impregnated geysers, or as sulphurous steam. It was easy to follow out the idea and conceive how these inflammably begot forces, confined in the interior and unable to escape, have raised the land into mountain-masses; or, as the material consumed, have caused the crust of the earth, sometimes gradually, at other times violently, to sink into the empty caverns. Hence earthquakes but wait upon the sulphur fires below, and attest their wide-spread power. Whether at boiling cauldron or bursting crater the only inflammable or explosive substance to be seen is Sulphur, and the only effect observable is that from its fire. Steaming basins, smoking craters, and destroying earthquakes, it may be safely assumed, never occur without the presence of Sulphur as the good or evil genius of the phenomena.
Rotomahana.—During the writer's stay at the Terraces he was favoured with an exhibition of the subsidence of the waters of Te Tarata into the caverns below; and as the Terraces on that occasion got dry, it was noteworthy how brittle the silicious surface became, showing upon what a slender thread the beauties of that mountain side hang; for, were the flow of the blue waters to stop, as stop it must when the energies of the forces below exhaust themselves, the glory as well as the cause of Rotomahana will disappear.
Tongariro (Ngauruhoe).—When the writer visited the crater of Tongariro in May of last year, there was a cone on the north-west side of it. This cone was about 120 feet wide at the top, and was closed at the bottom as if the volcano had not been in action for a considerable time. Upon the writer's climbing the mountain (a feat always attended with difficulty and risk) and descending into the orater, in December following, he found that
the above cone had completely vanished, and that along the greater part of the north side of the crater another cone, about 500 feet wide at the top, had been violently thrown up. In the interior of this cone, at the bottom, there were two openings opposite each other, out of which sulphurous steam was blown in considerable quantities. The outside of the cone was of loose material, as might be expected from its recent deposition, and was composed of stones, pumice, cinders, and debris of the mountain.
It is thus evident that this volcano is still active, although at uncertain periods. Over the floor of the crater, and up aloft, along the sides, as well as outside the mountain, sulphur-steam was issuing in all directions, tinging the orifices with yellow crystals of sulphur. The whole crater of Tongariro might be 1500 feet wide. The loose burnt sides, overhanging the floor, are gradually falling down, altering the configuration of the summit of the mountain. Upon the floor of the crater there were several thick patches of hardened snow; and at the north side, under the cliffs, a large wreath of snow, melting from the heat beneath, formed a singular-looking cavern with a scalloped roof, as of white marble. The writer spent a night inside the crater, and found the air intensely cold till the sun rose high enough in the morning to shine into the crater. Astronomers, in scanning the volcanoes of the moon, have noticed about the middle of the floor of certain craters a small cone, giving rise to speculation about its cause. Does not Tongariro afford explanation—that, as the volcanic forces exhaust themselves, they give vent to their expiring fires by a small cone.
White Island.—It is generally supposed that the vapours arising from White Island are steam from geysers; whereas, sulphurous steam never rises to any height. The main forces of the grand display at the “Theatre of Nature” upon White Island, are burning beds of sulphur, which show their red fires at night across the lake, whilst the fumes rise up into the air in volumes, to spread there at a great height, like a balloon, or to flow away in a train over the sea before the breeze.