titude and season influenced the na- 
ture and extent of the damage suffered 
by different parts of the mountain. 
In May, much of the landscape was 
still covered with snow. By contrast, 
when I visited the volcano late in the 
summer of 1980 after a minor erup- 
tion, I found that hot-gas emissions 
had scorched exposed plants. These 
withered bits of straw provided an ink- 
ling of what might happen if a big 
eruption occurred when there was no 
snowpack to cushion the blow. 
The May 18 eruption, like subse- 
quent smaller eruptions, was a series 
of events, each producing different 
conditions. In some places, biotic re- 
covery has begun with survivors; in 
others, colonizers from outside the im- 
pacted zone are required. Many eco- 
systems won’t return to anything re- 
sembling their preeruption state for 
years. But almost all affected ecosys- 
tems are showing resilience, and the 
message is clear: while it took a beat- 
ing, life was never obliterated from 
Mount St. Helens. 
The eruption, which followed two 
months of relatively minor volcanic 
activity, unexpectedly concentrated 
its force on the land to the north. 
Although geologists had anticipated 
a major eruption and the magnitude 
of the blast was not unprecedented, 
no one was prepared for the degree 
of devastation spawned by the unusual 
lateral direction of the eruption. More 
than a cubic mile of ash was injected 
into the atmosphere, eventually coat- 
ing hundreds of square miles of forest 
and agricultural land. Millions of in- 
sects were knocked dead from the sky. 
Heat scorched trees up to sixteen miles 
north of the crater, and the blast blew 
down trees in an arc of 160 degrees, 
extending more than ten miles from 
the crater. In most areas within a six- 
mile radius of the crater all life was 
destroyed. Large, rapid mudflows, 
confined to the lower elevations of sev- 
eral of the mountain’s major stream 
systems, crested over twenty-five feet 
and buried the flood plains of the 
Muddy River to the east and both 
forks of the Toutle River to the west. 
A flow of hot debris then swept all 
life from the northern flank of the 
mountain and the upper Toutle Valley, 
creating an eerie moonscape. (Unlike 
the sterile surface of the moon, how- 
ever, the debris is rich in organic re- 
siduals.) Melting glaciers and snow- 
fields triggered smaller mudflows on 
the upper slopes. For example, on the 
southeast flank of the mountain, the 
James Lee. Earth Images 
melting of Shoestring Glacier caused 
a mudflow along Pine Creek that cov- 
ered vegetation on the edges of the 
creek while removing it from the creek 
bed. In total, the eruption of Mount 
St. Helens had a profound impact on 
a region of about 160 square miles. 
The number of animals killed as 
a direct result of the explosion was 
high. Subterranean animals, such as 
pocket gophers, appear to have sur- 
vived in many places even within the 
blast zone, but mammals and birds 
living above ground had no protection 
from the blast. The Washington De- 
partment of Game estimates that 
among the more prominent casualties 
were 5,200 elk, 6,000 black-tailed 
deer, 200 black bears, 11,000 hares, 
15 mountain lions, 300 bobcats, 
27,000 grouse, and 1,400 coyotes; the 
agency has estimated heavy additional 
losses due to ashfall. The eruption also 
severely damaged twenty-six lakes and 
killed some eleven million fish, includ- 
ing trout and young salmon. 
Animals outside the blasted areas 
must contend with altered habitats 
and reduced quantities and quality of 
food. In the blowdown zone, elk and 
deer are now common near water and 
where fresh forage has emerged from 
the ash. These survivors may have to 
forage more widely, but their reduced 
numbers will ease competition 
stresses. Zoologists expect the popu- 
lations of vertebrates to build up as 
the vegetation recovers, and they are 
hoping to determine how much the 
vertebrate pioneers may change their 
behavior with respect to habitat and 
resource use as their numbers in- 
crease. Significant changes in behav- 
ior would constitute evidence for in- 
terspecific competition, normally dif- 
ficult to observe in nature. 
38 
