Tech5 News: Earthquakes and Volcanoes: What seems new is old

Ben HarrisonEarthquakes and Volcanoes: What seems new is old

Good afternoon and welcome to another Tech 5 program and a five minute trip into the amazing world of technology. This is Ben Harrison.

I’d like to share with you some thoughts on volcanoes and earthquakes, the source of some of the earth’s greatest disasters and loss of life. Some of the earliest earthquake and volcanic disasters go back as far as recorded time and include the famous catastrophic eruption in 79 A.D. of Vesuvius that buried the towns of Herculaneum and Pompeiia and the Syrian earthquake that struck at about dawn on 20 May 1202 resulted in estimates of upwards of 1,100,000 deaths.

St. Vincent and the Grenadines has its own La Soufrière volcano that violently erupted in 1718, 1812, 1902, 1971, and 1979. The eruption of May 7, 1902, was just hours before the eruption of Mount Pelée on Martinique, which killed 1,680 people.

La Soufriere’s last recorded eruption was in April 1979 but due to advance warning there were no casualties. and ‘yes’ we can take comfort in knowing that we have a seismograph installation in St. Vincent that even recorded details of the tremor last week off Barbados.

The Eastern Caribbean Islands are particularly vulnerable to impact from submarine eruptions from an undersea volcano named “Kick-em-Jenny” which is located five miles north of Grenada, about 450 feet under water.

The first recorded eruption of Kick Em Jenny was in 1939, although it must have erupted many times before that date. On 23–24 July 1939 an eruption broke the sea surface, sending a cloud of steam and debris 902 ft into the air and generating a series of tsunamis around six feet high when they reached the coastlines of northern Grenada and the southern Grenadines. A small tsunami also reached the West coast of nearby Barbados, where ‘a sea-wave’ suddenly washed over a coastal road.

The Kick Em Jenny volcano has erupted on at least twelve occasions between 1939 and 2001 (the last being on December 4, 2001), although none of the eruptions have been as large as the 1939 one, and most were only detected by seismographs.

Also historical records have shown that a tsunami was generated by an earthquake in 1867 which affected St. Thomas and Tortola in the Virgin Islands.

How do we know when an earthquake has happened or is imminent?

Earthquakes generate seismic waves that are detected with an instrument called a seismograph, that is being monitored 24/7. Through the years seismograph technology has advanced, but I bet you didn’t know that the earliest seismograph was invented in China 136 A.D. by a man named Zhang Heng.

Zhang’s machine was a mix of science, art, and tripping balls: a big bronze pot with dragon statues watching in eight directions, each holding a bronze ball in its mouth. The dragon mouths were calibrated so that at the slightest tremor of the ground, the head closest to the source would drop its ball into the mouth of a toad at the base of the device, indicating not only the earthquake, but also the direction of the earthquake. Zhang called it his “instrument for measuring the seasonal winds and the movements of the Earth,” and it  worked. The machine was said to be capable of sensing an earthquake that was happening hundreds of miles away.

Volcanic eruptions and earthquakes can and do happen world-wide and many are so small that they do not even gain a mention on our daily news broadcasts

The earth is constantly moving because of which there is a continuous movement of rock. This movement of the earth’s rocks creates fractures or discontinuity which is better known as faults. The tectonic forces at work within the rock create large faults resulting in the release of energy

The earth’s outer shell is divided into seven major and some smaller plates which are constantly in a dynamic state, pushing against, pulling away from, or grinding past one another. Forces build up as the plates attempt to move in relation to each other. When the adhesions along the fault give way, stored energy is released in the form of earth tremors, volcanic activity etc. Seismographs record and measure all this activity.

Early warning systems and emergency preparedness organisations like NEMO are the key to survival and minimization of loss of life and property, when a natural disaster strikes.

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This is Ben Harrison from EEZEE Radio 91.1 AND 102.7 on your FM DIAL in St. Vincent and the Grenadines