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Earthquakes and Tsunamis

It is surprising to learn that, according to reliable estimates, there are more than a million earthquakes every year! Mercifully, most of them are so small or occur in such remote corners of the globe that they escape detection. Even so, as many as 20,000 earthquakes are recorded each year – that’s approximately 50 a day!

The earthquake which occurred on 26th December 2004 was the strongest for four decades (measuring 9.0 on the Richter scale) and one of the strongest since records began in 1899. Not since 1964 has there been an earthquake registering nine or more on the Richter scale. The quake in that year, which occurred on 28th March in Alaska, registered 9.2 and was even larger than another earthquake Alaska had suffered just a few years previously, in 1957, which had registered 9.1. But neither of these heads the list of the strongest earthquake ever recorded – that dubious accolade goes to the quake which occurred in 1960 in Chile and registered 9.5 on the Richter scale.

All of these earthquakes caused "tsunamis" (sometimes called "tidal waves" although they have nothing to do with the tides). Tsunamis occur when something happens to cause a large displacement of water in the sea--a volcano erupting under the sea, for example, or two of the plates that form the Earth's crust slipping as they press against each other (as happened in the recent earthquake which had its epicentre near the Indonesian island of Sumatra).

Tsunamis are capable of travelling at speeds of over 900 kilometres an hour, at least in deep water. However, they slow down as they near land and shallower water, becoming higher in the process and creating the "wall of water" effect. Even so, tsunamis can still be travelling at speeds in excess of 50 kilometres per hour when they reach the beaches. Perhaps the most famous tsunami up to now is that which followed the eruption of the volcano Krakatoa on 27th August 1883--an enormous wave that swept over the ill-fated Indonesian islands of Java and Sumatra.

7. Listening. Reading Explorer 3. Text 12A.

Texts for translation from Russian into English

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