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yards, but the method does not appear to 
have been employed against lava flows (F. M. 
Bullard, personal communication, 1956) . Ex- 
cept for the barriers built in 1955, described 
on a later page, I know of only one other de- 
liberate attempt to control a lava flow by 
means of a walk In 1951, lava flows from 
Mihara volcano, Japan, accumulated in the 
Oshima caldera and approached the level of a 
low gap in the caldera wall directly above the 
village of Nomashi. In an effort to prevent the 
lava from spilling through the gap and threat- 
ening the village, the villagers constructed 
across the gap a masonry wall (Fig. 2) 15 
meters long, 2 to 4 meters high, and 3 meters 
thick (Mason and Foster, 1953: 257). The 
wall was intended to impound the lava like a 
dam, until the lava reached a level at which it 
would spill through another nearby gap where 
it would not threaten the village. The eruption 
stopped before the lava reached the wall, but 
there is every likelihood that the wall would 
have accomplished its purpose. 
Several examples of lava flows coming in 
accidental contact with stone walls have been 
observed. In 1906, an aa lava flow invaded the 
town of Boscotrecase, on the south slope of 
Vesuvius, and entered the churchyard which 
was enclosed by a masonry wall about 10 feet 
high. The lava filled the churchyard nearly to 
the level of the top of the wall, but did not 
damage the wall ( Jaggar, 1945: pi. 1). Nearby, 
lava moving along the village streets did not 
seriously disturb the walls of the adjacent 
buildings (Fig. 3). Most of the damage to the 
masonry, visible in Figure 3, was caused by 
fire in the buildings. (At other places build- 
ings were seriously damaged, especially where 
the walls lay at right angles to the direction 
of advance of the flow.) 
Fig. 2. Masonry wall built across a gap in the wall of Oshima caldera, Jap'an, in 1951, to prevent lava from 
spilling through the gap and endangering the village of Nomashi. Photo by Helen L. Foster, U. S. Geolog- 
ical Survey. 
