1 Be aware
2Take precautions
242
NATURAL DISASTERS
Tsunami
For FLOOD see p. 228 For EARTHQUAKE see p. 238 An earthquake, volcanic eruption, or underwater landslide can cause a tsunami: a series of underwater waves that sweep towards shore, sometimes rising to heights of over 100 ft( 30 m), and causing immense damage. A“ tsunami advisory” indicates that a tsunami is possible; a“ tsunami watch” that a tsunami may be 2 hours away; and a“ tsunami warning” that giant waves may be imminent. If you live within 2 miles( 3.2 km) of the shore and your house stands less than 100 ft( 30 m) above sea level, evacuate as soon as you receive a“ tsunami warning” and move to high ground as far inland as you can go.
PREPARING FOR A TSUNAMI
1 Be aware
• Keep alert for a“ tsunami advisory” or“ tsunami watch,” and listen to local radio stations for updates.
• Check that your planned escape route is clear.
• Familiarize yourself with warning signs, such as a sudden change in the level of coastal waters.
• Tsunamis often cause severe floods; make sure that you are prepared to cope( p. 228).
2Take precautions
• Keep your car filled with fuel so that you can drive to safety at a
moment’ s notice.
• If a“ tsunami watch” turns into a“ tsunami warning,” prepare to
evacuate your home.
• Coastal areas within 1 mile( 1.6 km) of the sea and less than 25 ft
( 7.5 m) above sea level are most at risk; make an early assessment of the best route to higher ground.
UNDERSTANDING TSUNAMIS
• Earthquakes, underwater landslides, or volcanic
eruptions can cause tsunamis.
• Each tsunami consists of a series of waves travelling at
speeds of up to 600 mph( 970 km / h).
• These waves are hundreds of miles( kilometers) long but
only a few feet( about a meter)“ tall” as they travel the ocean floor. Hence, they cannot be detected from the air or at sea until they near the shore.
• Seismic activity may be the only advance warning of an
approaching tsunami.
• As the tsunami nears the coast, the waves slow down
and increase in height.
• Before the first wave reaches the shore, the sea may be
dramatically“ sucked” away from the shoreline.
• Successive waves appear at intervals of 5 to 90 minutes.
• The first wave is usually not the largest; the following ones
cause the most damage.
Sea-borne disaster Vast sea waves crash onto the shore, causing damage and claiming lives.