EARTHQUAKES AND GEYSERS 365 
Let us suppose that the boiling-point of the water at a given 
depth below the surface, under the pressure of the column of 
water above, is 230°, The 
water here is warmed 
until this temperature is 
reached, when it begins 
to change to steam. 
Since the narrow tube 
prevents its ready escape, 
the steam lifts the water 
in the tube, causing some 
of it to overflow. Thus 
there is a loss of, we will 
suppose, several pounds 
of water, and hence a 
release of just that much 
pressure. So the boiling- 
point at the place under 
consideration is suddenly 
lowered to 228°. There- 
fore, the water here has 
a temperature higher 
than the  boiling-point 
for that particular press- 
ure, and nothing re- 
mains for it to do except 
to suddenly change, with 
explosive force, to steam. 
The length of time re- 
quired to bring about 
these peculiar conditions 
° ° 
° ° ° ° ° 9 
° ° 
SURFACE © bas Be 0 = re) 
1 ATMOS, Op a N a Oe er 
2 ATMOS. pre 
83.8 FT. D —$ g b 
SUPPLY OF HEAT 
3 ATMOS. 
66.6 FT. Pee SDE 
: y PRESSURE IN | BOILING ¢ 
ATMOSPHERES | POINT 
1 ATMOS.(SURFACE)) 212° 
2 ATMOS. (83.8 FT.} 250° 
3 ATMOS. (66.6 FT.)]| 275° 
4 ATMOS. F 
100 FT. fy 4 ATMOS. (100-FT.)| 293 d 
Fig. 223. 
Diagram to illustrate cause of geyser eruption. 
Horizontal divisions, degrees of temperature ; 
vertical divisions, depth in feet and pressure 
expressed in atmospheres (one atmosphere 
about 15 pounds to the square inch). Boiling- 
points for the different pressures given in the 
table. Line af represents temperature in gey- 
ser tube at depths down to 100 feet. This is 
always below the boiling-point for the depth. 
The curve of boiling-point at different depths, 
and hence different pressures, shown by line ed. 
Asupply of heat raises the temperature of a part 
of the line a/, at gh, until it reaches the boiling- 
point at 7, about 40 feet below the surface. Then 
steam is formed, and shortly an explosion. 
determines the period of the eruption, which may be regular and 
frequent, or on the other hand, very irregular. 
