THE GEYSERS OF NEW ZEALAND.
The geysers of New Zealand are situated in a region clothed with a luxuriant vegetation that is in strong contrast to the bleak and barren lava fields of Iceland, but an examination of the position of the springs, with respect to the physical features of the region, shows that the situation of the geysers is nearly the same in these antipodal isles. The New Zealand geysers occur in the North Island, in what is known as the volcanic region, or the Taupo zone. Within an area of 4,725 square miles, in which none but volcanic rocks are found, there are six volcanoes and great numbers of solfataras, fumeroles, mud volcanoes and hot springs, and many geysers. The lavas are all of the acid type, mostly rhyolite, but are hidden by surface decomposition and an abundant vegetation, save upon the flanks of the peaks. The axial line of this zone running northeast is marked at each end by an active volcano and its course by a line of greatest hydrothermal activity, a sinuous line of hot springs following well-marked geographic features of river valleys, low plains, and lake margins, with higher country on either side rising to plateaus of 2,000 to 3,000 feet above the sea.
Little is known of the geysers on the shores of Lake Taupo or those on the banks of the Waikato River, but the famous terraces of Rotomahana, called the eighth wonder of the world by James Anthony Froude, attracted attention to the geysers which formed them, and made their vicinity the best-known part of the district. The warm lake called Rotomahana by the Maoris was a shallow body of warm water about a mile long and a quarter of a mile broad, comprising 185 acres. The waters were of a dirty greenish hue, reflecting the somber green of the fern and the ti-tree-covered slopes about it, and the sedgy margins sheltered large numbers of duck and other water fowl. Rising above its surface like stairways of delicately sculptured marble were the pink and white terraces. At the top of the terrace, 120 feet above the lake, was the Terata Geyser, whose overflow had built up this wonderful work and filled the basins and pools with waters whose tints were both the delight of the eye and the despair of the pen.
The geyser caldron was some 60 by 80 feet across, its clear and boiling water usually overflowing and occasionally ejected to a height of 40 to 100 feet, wetting the steep banks of bright-colored fumerole clays about the crater but not forming the beaded geyserite characteristic of so many of these fountains. Such eruptions followed a period of quiescence, when the waters retired within the pipe for many hours. Owing to the comparative inaccessibility of the caldron and the beauty of the terraces, but few observations are on record of the action of the geyser. The water carried 150 grains of solid matter to the gallon, of which one-third was silica, and the daily outflow of 100,000 to 600,000 gallons per hour brought up 10 tons of solid matter dissolved out of the underlying rocks. It is easy to see what great underground caverns would be formed by this geyser alone in a comparatively brief time. In the volcanic outbreak of Tarawera, in June, 1886, the waters of the lake and underground reservoirs were drawn into the newly opened fissure, and, by the extraordinary explosion that followed, the terraces were destroyed and the site of Rotomahara became a crater that threw mud over the surrounding country.
Last Updated: 02-Apr-2007