• A tsunami is a series of ocean waves that are
usually caused by earthquakes.
• The word tsunami is a Japanese word. It means
‘harbour wave’ with ‘tsu’ meaning harbour and
‘nami’ meaning wave.
• Tsunami are usually formed by undersea events
that create sudden and large disturbances to
the water in the ocean.
• Undersea earthquakes that cause massive changes to the ocean
floor and the displacement of a large volume of water are the
most common cause of a tsunami.
• When an undersea earthquake or other major disturbance
causes a section of the ocean floor to suddenly rise or sink, the
mass of water above the affected area also rises or sinks.
• This unexpected movement of the water creates a series of
powerful waves.
• A tsunami can also be caused from events above the ocean
floor.
• More than 75 percent of tsunami are caused by undersea
earthquakes.
• Most tsunami occur in the Pacific and Indian Oceans. The
boundary of the Pacific Ocean experiences frequent
earthquakes and is commonly known as the Ring of Fire.
• As a tsunami wave approaches land and moves into more
shallow water, the leading edge of the wave slows down but the
back of the wave is still travelling at its original speed. This
causes the water to bunch up and increase the wave height. This
is known as ‘shoaling’.
• When it reaches land, it may behave like a series of breaking
waves or one large, powerful wave. The tremendous energy of
the wave can cause great quantities of water to surge inland,
far beyond where even the highest of tides would usually reach.
• Some of the largest tsunami waves were generated by the
volcanic eruption of Krakatoa in 1883, reaching a height of
37m.
• In 1737, a tsunami was estimated to be 64m high as it struck
Cape Lopatka in north-east Russia.
• On March 11, 2011, a magnitude 9 earthquake shook northeastern Japan, unleashing a savage tsunami.
• Residents of Tokyo received a minute of warning before the
strong shaking hit the city.
• Less than an hour after the earthquake, the first of many
tsunami waves hit Japan's coastline.
• The tsunami flooded an estimated area of approximately
561 square kilometres in Japan. The waves overtopped and
destroyed protective tsunami seawalls at several locations. The
massive surge destroyed three-story buildings where people
had gathered for safety.
• More than 18,000 people were killed in the disaster. Most died
by drowning.
• http://video.nationalgeographic.com.au/video/news/japantsunami-2011-vin