EARTHQUAKES AND GEYSERS 363 
Park of Wyoming, some of the hot springs have the 
habit of intermittent eruption; they are then called 
geysers (Fig. 220). These are crater-like springs of hot 
water, often surrounded by a cone of silicious sinter of 
their own building (Fig. 221). Most of the time the 
geysers are mere springs, but at certain intervals they 
eject water and steam high into the air. 
After an interval, sometimes of a few minutes or 
hours, and again years, 
these geysers break forth, 
and from their outlet 
issues a column of steam, 
rising sometimes to a 
height of one or two 
hundred feet. Before the 
eruption commences, the 
water boils; and at all 
times water with a tem- 
Fig. 221. 
perature nearly ab the siticious crater of geyser in Yellowstone 
boiling-point is present Park. 
in the spring. That these geysers are only a special 
kind of hot spring, is shown by the fact that in the 
Yellowstone Park, a geyser (the Artemesia) has de- 
veloped from a hot spring since the Park was set 
aside for the public. | 
Somewhere there is a source of heat, which seems 
to be located at no great depth (Fig. 222). Perhaps 
