Lava Barrier at Hilo — Wentworth, Powers, and Eaton 
353 
be expected for several decades, based on the 
spacing of recent known eruptions: 1740?, 
1793?, 1840, and 1955 (Macdonald, 1941). 
Forecasts of Mauna Loa activity based on an 
even shorter period of time may be equally 
wrong; in fact, an inspection of a longer record 
shows that the activity of Mauna Loa waxes and 
wanes in a manner that gives no useful basis for 
predicting the frequency of future activity. In 
the 180 years since 1780 there have been 20 
lava flows from the flanks of Mauna Loa; in the 
preceding 600 odd years covered by Hawaiian 
oral traditions there apparently were no lava 
flows from Mauna Loa; and, representing activ- 
ity previous to A.D. 1100, 60 different ancient 
cinder cones can be found that indicate flank 
eruptions that took place over an unknown span 
of time. There is no geological basis for pre- 
dicting how long the present epoch of frequent 
eruption may last; it may continue or it may 
have run its course. 
The evidence for the dormancy of Mauna Loa 
during about 600 years covered by Hawaiian 
oral history is considered here in some detail, 
as it has not had the attention in the literature 
that it deserves. It consists of the evaluation of 
observations by early explorers and of geologists 
and evaluation of Hawaiian oral history and 
mythology. 
Members of Captain Cook’s expedition in 
1778-79, particularly John Ledyard who at- 
tempted to climb the mountain, noted that 
Mauna Loa was a volcano and described features 
on the slopes ”... that had every appearance of 
past eruption and fire. . . . But there is no tradi- 
tion among the inhabitants of any such circum- 
stance” (Hitchcock, 1909: 61-62). 
Archibald Menzies, the botanist on one of 
Vancouver’s expeditions, climbed to the sum- 
mit crater of Mauna Loa in February, 1794; he 
contrasts "the Mountain” Mauna Loa with "the 
Volcano” Kilauea in his descriptions (Hitch- 
cock, 1909: 68-72). 
William Ellis, a British missionary who knew 
the Polynesian language, explored Hawaii in 
1823 and queried the Hawaiians about volcanic 
activity. They had no oral history of lava flows 
from Mauna Loa but reported that Kilauea had 
been active from "time immemorial” and that 
some part of the lands of Kau and Puna had 
been devastated by a lava flow during the reign 
of every King (Hitchcock, 1909: 163-164). 
The United States exploring expedition under 
Captain Wilkes spent nearly a month on the 
summit of Mauna Loa in the winter of 1840-41, 
having traversed the northeast ridge in the as- 
cent (at that time, only one of the known his- 
toric eruptions had broken out from this re- 
gion). They reported that the whole area was 
of lava, chiefly of very ancient date ( Hitchcock, 
1909: 83). 
A large area of the southwest ridge of Mauna 
Loa was explored by R. H. Finch of the U.S. 
Geological Survey during December, 1925. He 
observed, "The lava on the southwest flank of 
Mauna Loa may well be divided into two ages: 
recent (within the last 100 to 150 years, say), 
and old. Lava flows of various ages showing a 
uniform gradation in weathering between the 
oldest and newest flows are not to be found” 
(Finch, 1925: 90). 
There is thus some geologic evidence for a 
considerable period of dormancy of Mauna Loa, 
implied by the lack of mention of Mauna Loa 
flows in Hawaiian oral history. Moreover, recent 
seismological evidence that Kilauea’s lava rises 
from a zone about 60 km. beneath the region 
between the Kilauea caldera and Mauna Loa’s 
northeast rift zone raises the possibility that 
both volcanoes are fed from the same source 
and that when one is in a period of unusual ac- 
tivity the other erupts infrequently. Such alter- 
nation in activity between the two volcanoes 
over century-long intervals is suggested by the 
historic evidence quoted above. 
However, the Hawaiians were well aware of 
the fact that Mauna Loa was a volcano; many 
of their myths describing the activities of the 
demigods were explanations of volcanic features 
they found on the slopes of Mauna Loa. Pre- 
Hawaiian lava flows on the southwest slope are 
explained in the legend of "Na Pu'u o Pele” 
(Westervelt, 1916: 22-26); the lava flows that 
bank against the north slope of Mauna Kea 
were, to the Hawaiians, evidence of legendary 
conflicts between Pele and the snow-goddesses 
(Westervelt, 1916: 62); and the most recent 
lava flow in the forest south of Hilo was, to 
them, a record of the battle between Hi'iaka 
and Pana-'Ewa (Westervelt, 1916: 96-103). In 
