People in the Mountains - Mountain Geography: Physical and Human Dimensions - page 522

of earthquake risk in mountain environments. Together, they resulted in more than
150,000 fatalities, many more injuries, the temporary and permanent displacement of
millions of people from their homes, and billions of dollars of direct and indirect dam-
age costs. Each occurred in seismically active regions on the Indo-Australian and Eur-
asian continental plate boundary where earthquake disasters have had a long history.
They impacted cities and towns in valleys and mountain margin areas, remote moun-
tain villages, communications and transportation infrastructure, homes, public build-
ings, and spaces such as schools, hospitals, and clinics, as well as a wide range of eco-
nomic activities. Severe ground surface displacement and shaking in both cases pro-
duced an enormous cascade of landslides (over 4,000 in Kashmir and 3,800 in Sichuan)
that destroyed and damaged roads and settlements, thus further delaying and complic-
ating an emergency response already compromised by earthquake damage and adverse
weather. Landslides in both cases also produced landslide-dammed lakes, which imme-
diately posed a dam-burst flood hazard (Owen et al. 2008; Cui et al. 2011). Thirty-eight
such lakes were identified in the case of Sichuan, where there has been a long and tra-
gic history of dam-burst floods, requiring an immediate response of lake drainage and
dam hardening. However, this case illustrates a further hazard cascade characteristic
of mountain areas subject to intense monsoonal rainfall when, in mid-July/August 2010,
exceptionally heavy rains generated large and extensive debris flows in the earthquake-
exposed sediments, undoing much of the previous post-earthquake recovery and recon-
struction efforts, and creating a delayed disaster (Tang et al. 2011; Fig. 10.18). The
huge impacts, extensive and often isolated areas affected, and the frequent occurrence
of some earthquake disasters in mountain areas call upon a combination of local, re-
gional, and international resources.
Volcanic Hazards
Much, but not all, volcanic activity is expressed in the form of mountains, and some of
the most densely populated and intensively used mountain areas are on the slopes of
volcanoes in Ecuador, Mexico, and Indonesia. Though the areas around volcanic moun-
tains are most exposed to the hazards related to volcanic eruptions, the impact of erup-
tions can be global, in the form of ash clouds disrupting air travel and creating tem-
porary decreases in atmospheric temperature. The spatial distribution of active and
inactive volcanoes reflects that of crustal plate boundaries, particularly those where
oceanic and continental plates converge (subduction zones) and where plates diverge
(rifts). The “Pacific Ring of Fire,” which includes the western Cordillera of the Americas,
the Japanese Islands, the Philippines, and the Indonesian islands, is an example of the
former; the Mid-Atlantic Ridge, with Iceland, the Canary Islands, and the Azores, is an
example of the latter. The slopes of some volcanic mountains, particularly those in the
subtropics and tropics, attract people in large numbers for two reasons: They may offer
the best land available for settlement and agriculture as, under the prevailing weather-
ing conditions, some volcanic materials (e.g., ash) rapidly transform to very productive
soils. The agents of volcanic destruction include explosive blast effects, falling debris,
volcanic ash falls, flows of lava, and rapid downslope flows of very hot debris, ash, and
gases called pyroclastic flows. The volcanoes of the Indonesian island of Java have very
high population densities in an environment where periodic eruptions have produced