Explosive Eruption of Kilauea in 1924— Finch 
Jaggar (1924: 59) suggested that shatter¬ 
ing during engulfment may have allowed 
ground water to gain access to red-hot intru¬ 
sive bodies and have caused some of the 
explosions. 
The withdrawal of the lava and sudden 
rupturing of the conduit walls provided a 
means whereby water could suddenly gain 
access to the hot volcano system and set up 
a "flash boiler” mechanism. Next comes the 
question as to the possibility of suddenly in¬ 
jecting a sufficient quantity of water to pro¬ 
duce the explosions. The Olaa well (Dun¬ 
can, 1942) with a drawdown of 8 feet by 
continuous pumping showed an inflow of 
80 gallons a second. If a void with the same 
capacity as that of the sump below the water 
surface were suddenly created, the amount 
of water rushing in during the first half 
second, say, might well be several times that 
of any half second after pumping had been 
in progress for some time. Likewise the dis¬ 
charge from water trapped in a dike com¬ 
partment, when the wall separating it from 
a volcano conduit is suddenly ruptured, 
might greatly exceed that of the next half 
second. A considerable vertical range in the 
shattered conduit would speed up the inflow 
of water, for the velocity of inflow varies 
roughly as the square root of the depth below 
the surface of the water table. 
The potency of volcanic heat in producing 
steam blasts, when the conditions that keep 
water out of the system are upset or dis¬ 
turbed, is easily understandable. A cubic 
foot of water at a pressure of 1 atmosphere 
and a temperature of 1700° F. would yield 
over 5,000 cu. ft. of steam, or with a con¬ 
stant volume would produce a pressure of 
80,000 lb. per sq. in. It should be noted, 
however, that only a small part of the heat 
of the rock would be available for any one 
explosion. The available heat in a "flash 
boiler” system would be limited to a surface 
layer about y 8 inch thick. 
239 
With the temperature of the rock known 
(about 1700° F.), by assuming some surface 
area it is easy to compute the available heat 
and then calculate the amount of water that 
could suddenly be converted to high-pressure 
steam. Suppose that an explosion were ini¬ 
tiated by the formation of a crack where the 
hot portion of the wall separating the con¬ 
duit from trapped ground water was 30 ft. 
thick. The surface of the hot rock in the 
walls of such a crack if 5 to 10 ft. wide and 
70 ft. high, together with fragmental mate¬ 
rial within the crack, could easily exceed 
6,000 sq. ft. This surface area and a thick¬ 
ness of y 8 inch would give a volume of 62.5 
cu. ft. With a specific gravity of 2.5, such a 
volume of rock would weigh about 10,000 
lb. The number of available B.T.U. above 
212° F. in 10,000 lb. of basalt with an ini¬ 
tial temperature of 1700° F., if we assume 
the specific heat is 0.30, is 4,470,000. Tak¬ 
ing the final temperature of the boiler sys¬ 
tem as 900° F.—on several occasions the 
dust of the explosion was observed to glow 
as it cleared the crater rim—the pressure 
generated could exceed 40,000 lb. per sq. in. 
This is many times the minimum require¬ 
ment mentioned above. The temperature of 
the steam as it was produced may have been 
above 900° F., with a resulting greater pres¬ 
sure. 
After the explosion pressure had dissipated 
in the case outlined above, another injection 
of water could produce another explosion in 
the same place. Progressive shattering of the 
conduit wall in either a vertical or horizon¬ 
tal direction could account for the series of 
explosion bursts that were noted on several 
occasions. The rocks of each explosion were 
largely confined to one sector of the ground 
around Halemaumau. All sectors were event¬ 
ually covered with explosion debris. This 
fact would indicate that the shattering was 
more or less piecemeal, first on one side of 
the pit, then on another. The amount of 
