New Zealand--Boiling Fountains and Lakes
In the eruptions of mud volcanoes, described in the foregoing
chapter, a frequent ingredient is boiling water. There are,
however, several instances in which there are thrown up jets of
boiling water that are not intermingled with mud, but in which the
water is either pure or impregnated with some mineral which it
holds in perfect solution. Of this nature are the Geysers of
Iceland and California, already described.
In New Zealand there is another variety of this phenomenon, the
boiling water issuing forth, not in intermittent jets, as in the
Geysers, but in perpetually flowing springs, forming lakes, in
which the water remains nearly at the boiling point. These springs
and lakes occur at a place called Roto-Mahana. The annexed woodcut
will convey an idea of their appearance.
There are several basins raised one above another, and all higher
than the level of the large lake. The highest is of an oval form,
and about two hundred and fifty feet in circumference. It is filled
from an opening at the height of about a hundred feet above the
level of the lower lake. At various stages below this upper basin
are numerous other springs, from which several similar basins are
filled. The whole of these basins empty themselves into the large
lake below, and the water in all of them is nearly boiling hot,
giving forth, with a hissing sound, volumes of white vapour.
[Illustration: Boiling Lakes of Roto Mahana]
These waters are richly impregnated with carbonate of lime, which
has formed all round the margins of the basins beautiful
incrustations of snowy whiteness. The sand round the lake is very
warm; and if a stick be thrust into it, jets of steam arise.
Doubtless, some years hence, the enterprising English settlers will
establish hot baths here. Not far from the lake there are smaller
basins, in which the water is not beyond what would be agreeable
for a warm bath; while it is of a blue colour and beautifully
clear.
On both banks of the river Waikato, also in this neighbourhood, are
found numerous basins full of boiling mud or slime, which cannot be
approached save with extreme care, owing to the softness and
slipperiness of the soil. The largest of these basins is oval in
form, 14 feet long by 8 feet wide, and about as much in depth. It
contains hot mud of a bright red colour, being strongly impregnated
with oxide of iron. Large viscous bubbles are continually rising to
the top, and on bursting they emit a fetid, sulphureous smell.
These phenomena are nearly akin to those of a mud volcano.