The New Zealand Railways Magazine, Volume 3, Issue 4 (August 1, 1928)
Why Geysers Gush
Why Geysers Gush.
Professor J. W. Gregory, a learned authority, puts the matter very clearly and succinctly when he states that “hot water at the bottom of a tube may be prevented from boiling, and thus kept superheated, by the weight of the water in the upper part of the tube. If the pressure be suddenly removed, then the water will burst into steam with explosive violence, and the water in the upper part of the tube will discharge in a geyser-like jet.”
If the water in the bottom of a geyser well is superheated, and either the load be reduced, or the water be heated to a temperature at which the weight of the overlying mass is insufficient to keep the lower water liquid, then the geyser will discharge by a sudden eruption.
The supply of further heated water from subterranean feeding channels to the bottom of the tube will raise the temperature of the water therein above the limit of superheating at that depth and it will therefore burst into steam and lift the whole of the water in the well.
.jpg)
To Geyserland!
Auckland-Rotorua Express.
It will be recognised that, given a plentiful supply of superheated water or steam, and a long tube of comparatively small section, geyser-action is probable. Occasionally, however, the conditions may not be conducive to condensation and the steam escapes in a continuous jet. The famous Blow-Hole of Kerapiti at Wairakei is an outstanding example.
In the case of geysers, the water near the surface tends to lose its high degree of temperature and in just such time as is necessary for the superheated steam or waters in the depths of the well to attain sufficient force to overcome the pressure of the heavier surface water, geyser-action is not only possible, but inevitable.
This, then, is the explanation of the more or less regularly intermittent nature of the displays, and the cause of eruption.
A geyser in a state of quiescence or equilibrium may frequently be brought into action in the following ways:
(a) By removing the pressure on the superheated depths through baling out the surface water, or
(b) By lowering the specific gravity of the surface water and its tension. (The popular method is to place soap in the geyser well.)
There are many theories bearing on the origin of the superheated water or steam. Some hold that it is derived from surface percolations which have penetrated deep down into that central magma—the heated “bowels of the earth”—which it is believed forms the core, as it were, of the globe, while others aver that it comes from the primaeval waters imprisoned in that central magma.