Page 59 - Environment: The Science Behind the Stories

Figure 2.20 Most of our
planet’s volcanoes and earth-
quakes occur along the circum-
Aleutian Pacific belt, or “ring of fire.”
Japan Islands In this map, red symbols indicate
Mt. Rainier
Mt. Fuji major volcanoes, and gray-shaded
Mt. St. Helens areas indicate areas of greatest
Mt. Lassen earthquake risk.
Mt. Popocatepetl
Mt. Mauna Loa
Mt. Pinatubo Mt. Kilauea What similarities do you
note between the “ring of
Mariana Trench fire” around the edges of the
Pacific Ocean and the boundaries
Mt. Mayon
San Andreas Fault of the tectonic plates shown in
Figure 2.16? Which of type of plate
Mt. Cotopaxi boundary (see Figure 2.17) is most
common along the length of the
Mt. Krakatoa “ring of fire”?

Mt. Tambora

Earthquakes result from movement the subsequent tsunami) were minimized thanks to Japan’s
at plate boundaries and faults embrace of earthquake-conscious building designs.

Along tectonic plate boundaries, and in other places where
faults occur, Earth may relieve built-up pressure in fits and Volcanoes arise from rifts, subduction
starts. Each release of energy causes what we know as an zones, or hotspots
earthquake. Most earthquakes are barely perceptible, but as
shown by the Tohoku quake of 2011, they are occasionally Where molten rock, hot gas, or ash erupts through Earth’s sur-
powerful enough to cause significant losses of human life and face, a volcano is formed, often creating a mountain over time
property (Table 2.2). Damage is generally greatest where soils as cooled lava accumulates. As we have seen, lava can extrude
are loose or saturated with water—areas of cities built atop
landfill are particularly susceptible. For instance, during the
1989 Loma Prieta earthquake, which shook San Francisco and Table 2.2 examples of large or recent earthquakes
Oakland while their baseball teams were playing in the World Year Location Fatalities Magnitude 1
Series, one of the areas hardest hit was San Francisco’s Marina 1556 Shaanxi Province, China 830,000 ~8
District, a neighborhood built atop soil and debris dumped 1755 Lisbon, Portugal 70,000 2 8.7
into the bay, including rubble from the city’s 1906 earthquake.
To minimize damage from earthquakes, engineers have 1906 San Francisco, California 3,000 7.8
developed ways to protect buildings from shaking. They do 1923 Kwanto, Japan 143,000 7.9
this by strengthening structural components while also design- 1964 Anchorage, Alaska 128 2 9.2
ing points at which a structure can move and sway harmlessly 1976 Tangshan, China 255,000+ 7.5
with ground motion. Just as a flexible tree trunk bends in a 1985 Michoacan, Mexico 9,500 8.0
storm while a brittle one breaks, buildings with built-in flex- 1989 Loma Prieta, California 63 6.9
ibility are more likely to withstand an earthquake’s violent
shaking. Such designs are an important part of new building 1994 Northridge, California 60 6.7
codes in California, Japan, and other quake-prone regions, and 1995 Kobe, Japan 5,502 6.9
many older structures are being retrofitted to meet these codes. 2004 Northern Sumatra 228,000 2 9.1
Such designs are more expensive to build than conven- 2005 Kashmir, Pakistan 86,000 7.6
tional designs, so many buildings in poorer nations do not 2008 Sichuan Province, China 50,000+ 7.9
have such protections. One example is Haiti, where a 7.0
magnitude earthquake in 2010 devastated huge portions of 2010 Port-au-Prince, Haiti 236,000 7.0
the capital city of Port-au-Prince and claimed an estimated 2010 Maule, Chile 500 8.8
230,000 lives (Figure 2.21). While the Tohoku earthquake 2011 Northern Japan 19,000 2 9.0
released over 950 times more energy than the earthquake that 1 Measured by moment magnitude; each full unit is roughly 32 times
struck Haiti, mortality and property damage from the Tohoku as powerful as the preceding full unit.
58 quake (not including the damage and loss of life caused by 2 Includes deaths from the resulting tsunami.

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