By Dr Reese Halter
Tsunamis (pronounced soo-NAH-mee) is a Japanese word meaning “habor wave”. They can be a single wave but more likely a series of waves. When they land onshore they are truly killer waves.
Tsunamis are triggered by submarine earthquakes, landslides, volcanic eruptions and even meteorite impacts. In the open ocean the waves are small, and they can travel thousands of kilometers at speeds of 603 miles per hour or as fast as a jet plane can fly.
When a tsunami approaches a shoreline the speed of the waves can slow down to 99 miles per hour. The shallow coastline causes the water beneath the wave to pile up. The roiling waves rise higher and higher. Within seconds, a two-foot wave at sea can become a 30-foot wave onshore.
Usually there are several waves in a row called a wave train. The third or fourth is often the highest but sometimes it’s the eighth or ninth wave. A tsunami can last for more than 8 hours.
Tsunamis are not related to weather nor climate change. They have been incorrectly called tidal waves; these waves are unrelated to tides.
Tsunamis are not seasonal, and can occur at any time of year in any ocean. They can occur on sunny days or in the middle of the night. There are an average of five or six tsunamis worldwide every year.
Tsunamis are one of nature’s most unpredictable phenomena’s. More people have been killed by tsunamis in Hawaii than by hurricanes, earthquakes and volcanic activities combined.
In fact, there have been some treacherous tsunamis over the past 125 years.
For example, on August 27, 1883 a viscous volcanic eruption annihilated the tiny Indonesian island of Krakatau. The sonic boom from the explosion was heard more than eighteen hundred and sixty miles away. This potent eruption unleashed a tsunami with waves in excess of 131 feet high. At least 36,000 people perished.
On July 10, 1958 an earthquake measuring 8.0 on the Richter scale created an enormous landslide near Lituya Bay, Alaska. An entire slope of earth and rocks plunged into the bay, displacing a massive amount of seawater that raced up the opposite valley wall as high as 1,722 feet. It obliterated the entire forest in its path. Within four minutes, a 102-foot-high wave surged 7 miles to the mouth of the bay and then sucked fishing boats, building and people out to sea.
The third largest earthquake ever recorded at 9.2 on the Richter scale struck Alaska on March 27, 1964. It triggered a tsunami that killed at least 130 people some as far away as Crescent City, California. Sixteen hours later waves reached the Antarctica.
The most powerful earthquake ever recorded took place in southern Chile on May 22, 1960. It measured an astounding 9.5 on the Richter scale. It released ten times more energy than the 1980 eruption of Mount St. Helen’s. Eighty-two foot waves smashed into central Chile. Sixteen hours later a tsunami struck Hawaii killing 61 people, it moved east lambasting Japan and killing 132 people and then onto the Philippines where 32 people died.
The second largest earthquake this century measured 9.3 on the Richter scale, it occurred offshore Sumatra on December 26, 2004. The ensuing tsunami and its wave train killed at least 200,000 people in Asia and east Africa.
Interestingly, tree ring patterns from western redcedars growing along coastal Washington clearly showed that an earthquake occurred in January 1770. It measured between 9 and 9.3 on the Richter scale. When compared to Japanese tsunami records it was discerned to have taken place on January 26, 1770; and its exact time was pinpointed 10 hours before the unrelenting wave train pummeled the Japanese coastline.
Any sudden increase or decrease in the level of the ocean should be immediately interpreted as an imminent signal of a tsunami. Move to higher ground as quickly as possible. Do not return to low lying areas for at least 10 hours.
The occurrence of tsunamis is closely monitored in the Pacific from Hawaii, along the West Coast and Alaska, and with systems in Chile and Japan.
Small electronic devices placed on the Indian and Pacific Ocean floors’ relay seismic activity to buoys on the surface, which in turn communicate with a constellation of satellites orbiting Earth. This deep ocean assessment and reporting of tsunamis can be viewed at www.ndbc.noa.gov/dart.shtml
Preparing people for tsunamis is of paramount importance yet its fraught with difficulties. A few false alarms and people may not believe or heed official warnings.
Informing all people regularly, not just coastal communities, is very important, because many people who live inland occasionally visit the coast on holidays.
Dr Reese Halter is a public speaker and conservation biologist. His latest book is “The Incomparable Honeybee and the Economics of Pollination,” Rocky Mountain Books.