- 24 Dec 2018
- 3 min read
A tsunami killed more than 200 people and injured hundreds on the Indonesian islands of Java and Sumatra following an underwater landslide believed to be caused by the erupting Anak Krakatau volcano.
- Anak Krakatau is the island that emerged from the area once occupied by Krakatau, which was destroyed in 1883. It first appeared in 1927 and has been growing ever since.
- In August 1883, Krakatoa underwent one of the most violent volcanic eruptions in recorded history:
- Massive tsunamis with waves of up to 41m killed more than 30,000 people.
- Thousands more were killed by hot ash.
- The eruptions were equivalent to 200 megatons of TNT - about 13,000 times the nuclear yield of the bomb dropped on Hiroshima in 1945.
- World temperatures dropped by more than 1°C the following year.
- The volcanic island virtually disappeared.
- High seas as a result of the full moon also contributed to the strength of the waves.
- Tsunami warning buoys are positioned to warn about tsunamis originated by earthquakes at underwater tectonic plate boundaries and not for those by volcanoes.
- Moreover, the proximity of the volcano to the coast gave authorities very little time to act.
- Indonesia is prone to tsunamis because it lies on the Ring of Fire - the line of frequent earthquakes and volcanic eruptions that circles virtually the entire Pacific rim.
- Earlier in September, 2018 more than 2,000 people died when a powerful earthquake struck just off the central Indonesian island of Sulawesi, setting off a tsunami.
- Tsunami is a Japanese term meaning a harbor wave. It is also commonly known as killer waves.
- A Tsunami is not just a single wave but a series of ocean waves called a wave train caused by an underwater earthquake, by a volcanic eruption, landslide, rapid changes in atmospheric pressure, or a meteorite.
- However, tsunamis caused by volcanic activity are less frequent.
- Most tsunamis–about 80 percent–happen within the Pacific Ocean’s “Ring of Fire,” a geologically active area where tectonic shifts make volcanoes and earthquakes common.
- Tsunamis race across the sea at up to 500 miles (805 kilometers) an hour—about as fast as a jet airplane. At that pace, they can cross the entire expanse of the Pacific Ocean in less than a day.
- Since they are long wavelengths, they lose very little energy along the way.
- In December 2015, the UN General Assembly designated 5 November as World Tsunami Awareness Day.