Page 61 - Environment: The Science Behind the Stories

Table 2.3 examples of notable Volcanic eruptions
Year Location Impacts Magnitude 2
640,000 b.p. 1 Yellowstone Caldera, Wyoming, U.S. Most recent “mega-eruption” at site of Yellowstone National Park 8
6870 b.p. Mount Mazama, Oregon, U.S. Created Crater Lake 7
a.d. 79 Mount Vesuvius, Italy Buried Pompeii and Herculaneum 5
1815 Mount Tambora, Indonesia Created “year without a summer”; killed at least 70,000 people 7
1883 Krakatau, Indonesia Killed over 36,000 people; heard 5000 km (3000 mi) away; 6
affected weather for 5 years
1980 Mount St. Helens, Washington, U.S. Blew top off mountain; sent ash 19 km (12 mi) into sky and into 5
11 U.S. states; 57 people killed
1983–present Kilauea, Hawaii, U.S. Continuous lava flow 1
1991 Mount Pinatubo, Philippines Sulfuric aerosols lowered world temperature 0.5 °C (0.9 °F) 6
2010 Eyjafjallajokull, Iceland Ash cloud disrupted air travel throughout Europe 1
1 b.p. = years before the present.
2 Measured by the Volcanic Explosivity Index, which ranges from 0 (least powerful) to 8 (most powerful).

the continent deeply in ash. Although another eruption is not and heavy rains may saturate soils and trigger mudslides of
expected imminently, the region is still geothermally active; soil, rock, and water. However, mass wasting can also be
the park hosts fully two-thirds of the world’s geysers. brought about by human land use practices that expose or
loosen soil, making slopes more prone to collapse.
Most often, mass wasting erodes unstable hillsides, dam-
Landslides are a form of mass wasting aging property one structure at a time (Figure 2.23). Occa-
sionally, mass wasting events can be colossal and deadly;
On a smaller scale than volcanoes or earthquakes, another type mudslides that followed the torrential rainfall of Hurricane
of geologic hazard, the landslide, occurs when large amounts Mitch in Nicaragua and Honduras in 1998 killed over 11,000
of rock or soil collapse and flow downhill. Landslides are a people. Mudslides caused when volcanic eruptions melt snow
severe and often sudden manifestation of the more general and send huge volumes of destabilized mud racing downhill
phenomenon of mass wasting, the downslope movement of are called lahars, and these are particularly dangerous. A lahar
soil and rock due to gravity. Mass wasting occurs naturally,
buried the entire town of Armero, Colombia, in 1985 follow-
ing an eruption, killing 21,000 people.

Tsunamis can follow earthquakes,
volcanoes, or landslides

Earthquakes, volcanic eruptions, and large coastal landslides
can all displace huge volumes of ocean water instantane-
ously and trigger a tsunami. The 2011 tsunami that inundated
portions of northeastern Japan was not the only recent major
tsunami event. In December 2004, a massive tsunami, trig-
gered by an earthquake off Sumatra, devastated the coastlines
of countries all around the Indian Ocean, including Indone-
sia, Thailand, Sri Lanka, India, and several African nations.
Roughly 228,000 people were killed, 1–2 million were dis-
placed, and whole communities were destroyed (Figure 2.24).
Coral reefs, coastal forests, and wetlands were damaged, and
saltwater contaminated soil and aquifers, making it difficult to
restore the affected areas.
Those of us who live in the United States and Canada
should not consider tsunamis to be something that occurs only
in faraway places. A large tsunami struck North America’s
Pacific coast in 1700 following a huge earthquake in the
Figure 2.23 Landslides are frequent in sloping areas along
the California coast, particularly after heavy winter Pacific Northwest, and one following the Alaskan earthquake
rains saturate soils. Homes built on unstable slopes, such as of 1964 drowned over 100 people from Alaska to Califor-
these in Laguna Beach, Orange County, can be damaged or nia. Residents of Boston, New York, Washington, D.C., and
60 destroyed when slopes give way. other cities along the Atlantic coast could be at risk if an

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