Download Slide 1 - OnCourse

• Japanese word meaning tidal wave
• Large wave resulting from an under water earthquake or volcanic eruption
• The ocean’s floor becomes tilted somehow
• Tsunamis move across an ocean to the shore
• Wavelengths of 60 to 120 mi and may reach speeds of 800 km/h
• Upon entering shallow waters, the wave height grows rapidly
• Could go from a small as a 3 ft to more than 135 ft upon reaching shore
• Involves incredible energy because of the great volume of water affected
• Waves are capable destruction and death to coastal towns
• Entire towns have been destroyed (1896, Sanriku, Japan – pop 20K)
• Upon striking shore, a tsunami creates a number of waves with a period between
waves of 10 to 30 minutes
• Most originate along the Ring of Fire
• Area of volcanoes & seismic activity 24K mi long encircling the Pacific Ocean
• Since 1819, more than 40 tsunamis have struck the Hawaiian Islands
• Warning systems has been developed in areas such as Hawaii
• Hawaii is the highest risk area and averages one tsunami per year
• They expect one that causes major damage about once every seven years
• Alaska is another high risk area with an average of one every 1.75 years and a
major damageof causer every seven years
• Warnings are via seismograph records
• These help determine the location of where a submarine earthquake
occurred
• These usually originate in one of the deep trenches in the Pacific Ocean floor
One of the largest and most destructive tsunamis ever recorded traveled at least half
way around the world in 1883 after the collapse of Krakatoa, a volcano in Indonesia.
Waves up to 100 ft. high caused great damage along the coast of Sumatra.
In 1964, an Alaskan earthquake generated a tsunami with waves between 10 and 20
feet high along parts of the California, Oregon, and Washington coasts. It caused
more than 123 deaths and damage estimated at more than $84 million in Alaska
alone.