268 
PACIFIC SCIENCE, Vol. XII, July, 1958 
Fig. 6. Plan of the barriers built by Robert Yamada 
in an attempt to keep lava from destroying his coffee 
plantation, on March 22-24, 1955. 
might consolidate against the barrier to form 
a dam which would impound the main body 
of the flow against the barrier and cause it to 
spill over. To prevent that, a short barrier 
(Fig. 6, lA) about 150 feet long and 8 feet 
high was hurriedly built across the path of the 
rapidly advancing tongue. This short barrier 
was completely successful. Part of the flow 
was diverted eastward by it, but, more im- 
portant, the advance of the entire tongue was 
delayed, as had been hoped, until the main 
body of the flow had made contact with the 
main barrier farther west and the entire flow 
front had turned eastward along the main 
barrier. 
On completion of the first two barriers 
(Fig. 6, 1 and lA) construction was started on 
another (Fig. 6, 2) farther down slope and ly- 
ing at a more acute angle to the course of ad- 
vance of the flow. Barrier 2 was connected to 
barrier 1 by a short wall at its western end. 
This connection was a mistake because it 
prevented the full operation of barrier 2 and 
actually forced some lava to flow around its 
western end, thus partly defeating its purpose. 
Lava spilled over barrier 1, which as previously 
stated was built at too obtuse an angle to the 
path of the flow, and filled the space between 
barriers 1 and 2. On March 24 a strong flow of 
lava was observed by Eaton along the north 
side of barrier 2 and parallel to it. Some lava 
spilled over barrier 2, particularly near its 
western end where it was only about 6 feet 
high, and joined that flowing around its west 
end, but the main body of lava was diverted 
eastward. No lava reached barrier 4 (Fig. 6). 
Barriers 3, 3A, and 3B, to the west of barrier 
2 (Fig. 6), were poorly conceived and served 
no useful purpose. In particular, barrier 3B, 
which appears to have been an attempt to 
impound a flow tongue by heaping up a wall 
around it, was wholly ineffective. 
In spite of poor placement and hurried, in- 
adequate construction, the principal Yamada 
barriers were essentially successful. Very little 
lava passed barrier 2 in the direction of the 
coffee plantation, and even at the time of 
poorest operation of the barrier Eaton esti- 
mated that the velocity of flow of lava along 
the north side of the barrier was 5 times as 
great as that across it. Considering the much 
smaller depth of material crossing the barrier 
as compared with that in the channel behind 
it, this means that probably at least nine- 
tenths of the volume of the flow was diverted 
eastward parallel to the barrier. 
Unhappily, these courageous attempts at 
barrier construction on the part of the Ya- 
madas did not prevent the destruction of the 
coffee plantation. On March 27 another flow 
passed a quarter of a mile southwest of the 
barriers, and on March 28 it swept across the 
plantation and into the ocean. 
The Yamada barriers provided some im- 
portant lessons in barrier construction. In the 
first place, they demonstrated the amazing 
rapidity (and correlatively, the surprising 
cheapness) with which such barriers can be 
built by modern bulldozers in areas where con- 
struction material is abundant. The area was 
one of fairly recent aa flows, and large amounts 
of loose aa clinker could easily be pushed up 
(together with tree trunks and all other debris) 
into a wall. Careful observation by Eaton, 
Kamai, and myself revealed no signs of any 
yielding of the walls under the thrust of the 
lava flows. The short delaying barrier (Fig. 6, 
