FACTS ABOUT TSUNAMIS
Tsunamis are seismic sea waves. Their name is a Japanese word meaning ‘harbor waves’. They are often incorrectly called ‘tidal waves’ (rare events linked to tides). A tsunami is a series of traveling ocean waves of extremely long length and period. They are caused by under-sea events like earthquakes, landslides and volcanic eruptions; or by other natural events such as ocean meteorite impacts, or large landslides into bays or lakes. A tsunami is like the effect of a stone landing in a pond. Waves radiate out in ever-widening circles. As a tsunami crosses a deep ocean, length from crest to crest may be 150 km but the height may be under a meter, not felt by ships nor seen from the air, and may reach speeds up to 1,000 km/h. The waves’ energy extends from deep ocean floor to surface.
As tsunamis enter shallow water near coastlines, wave speeds drop as energy is compressed into much shorter distances. Wave heights increase dramatically up to 40 meters, threatening life and property, as they strike the shore with devastating force. Between multiple waves, which may vary in size, sea-level may actually drop well below normal. Great destruction may arise even though the tsunami may have been caused thousands of kilometers away.
Where Do They Occur?
Pacific Region - The majority of tsunamis occur in the Pacific Ocean, although they have occurred in all oceans of the world. In our region, areas most at risk include many Pacific Islands, New Zealand, and the heavily-populated coasts of Japan and Indonesia.
History of Tsunami Disasters
The worst tsunami disaster followed the volcanic eruption of the island of Krakatoa in 1883 when 35 metre waves crashed into Java and Sumatra, drowning 36,420 people! In 1896, a large tsunami killed 27,000 in Japan. Destructive tsunamis of recent times included one of Chilean origin in May 1960, drowned 1,000 people in Chile, Hawaii, the Philippines and Japan. From 1970 to 1997, tsunamis caused over 9,000 deaths, including 2,700 on the Indonesian island of Flores in December 1992. On 3 June, 1994, a tsunami took over 200 lives along the Indian Ocean coastline of Java.
TSUNAMI SURVIVAL (Safety Rules)
- If you hear that a strong earthquake has occurred, stand by for a possible tsunami emergency, and be prepared to move from low-lying coastal or lakeside areas to high ground at short notice. All tsunamis are potentially dangerous and destructive.
- When an official warning is issued, it means a tsunami actually exists. Some tsunami victims have dismissed such warnings as false alarms and died as a result.
- Approaching tsunamis are sometimes preceded by a rapid rise or fall in sea-level. This is nature’s warning and should be heeded. Vessels should head for deep water immediately.
- A small tsunami at one point on the shore can be extremely large a few kilometers away so don’t let the modest size of one make you lose respect for all.
- As a tsunami is not a single wave, stay out of danger areas until an official ‘all-clear’.
- Never go to the shore to watch a tsunami. If you can see it, you are too close to escape.
- Cooperate with your local emergency authorities if asked to evacuate.
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Kim Patra is a qualified Registered Nurse and Midwife that has been living and working in Bali for almost twenty years. She now runs her own private practice and medical referral service from her Kuta office. Kim is happy to discuss any health concerns with you and she may be contacted via e-mail at info@chcbali.com”.
