Ten Geologic Hazards - Geology - page 342

Damages from tsunamis include the destruction of property and vegetation from the
fast-flowing flood waters, as well as the inland water flow or runup into areas relatively
far from shore. Since the 2004 Indian Ocean tsunami, much research on tsunamis (and
their relation to earthquakes) has centered on predicting these events and building
warning systems to notify communities that may be in danger when a tsunami occurs.
Unfortunately, as the 2011 tsunami in Japan illustrated, the warning systems are most ef-
fective for regions that are far enough away to respond to warnings before being struck
by the massive waves.
Destroying Farmland and Coastal Bluffs:
Erosion
Compared to a volcanic eruption, tsunami, or earthquake, erosion may seem like noth-
ing to worry about. The truth is that you are more likely to be affected in your daily life
by soil erosion than you are by any of the more dramatic geologic hazards.
Erosion is the movement of sediments and soil due to wind, water, or other processes.
Erosion of soil is most common in areas that are cleared of vegetation (because plants
hold the soil in place), such as by overgrazing of herd animals or deforestation. After the
soil is removed, the land can no longer support vegetation — or crops — and it becomes
useless.
This situation is particularly hazardous in hot, dry regions where cropland,
food, and water are already scarce. The erosion of surface soils in such regions
has increased with warming global temperatures in the last century: The higher
temperatures reduce rainfall, leaving surface sediments more susceptible to re-
moval by wind and making life much more difficult for the people who live there.
Erosion from moving water, such as along rivers, streambeds, and coastlines, is also a
hazard and can lead to landslides by undercutting the angle of repose (see Chapter 12).
As the bluffs along rivers or the coast are eroded, any buildings sitting on them are in
danger of collapsing into the water below.