Earthquakes

Press, 20 September 1982, Page 16

Earthquakes

Sir.—The otherwise excellent article (“The Press." September 17) on the enigmatic New Madris earthquakes of 1811-1812 contained one important error. It stated that “Geologists now know that the Earth is divided up into a series of huge, rigid plates . .They do not. Many think in terms of “plates” but this is conceptual and may be wrong. Moreover, as Sir Harold Jeffreys has repeatedly pointed out, such plates must be strong, not rigid. I should like the opportunity to ask your readers, should they experience any earthquake, to note if any noises (“brontides”) or lights are heard or seen. I might add that in 1835 the (different) noise of the great eruption of Cosiguina on the Pacific coast of Nicaragua was heard in Jamaica, nearly 1500 km away and in one village 300 people "living in concubinage” immediately got married. Fendaltonians should beware.—Yours, etc..

A. R. CRAWFORD, Professor of Geology. September 17, 1982.

Lead-free petrol

Sir,—There should now be an accurate assessment of the cost of eliminating lead in petrol based on the refinery expansion and the synthetic petrol plant, to be done, prefer-

ably, by a neutral agency. The S6OM cost of going lead free with which we are constantly admonished, the Ministry of Energy admitting that the figure’is "still subject to modification." is totally misleading. The expanded refinery will still have to add 0.15 grams of lead per litre of petrol while any lead-free programme would be, of necessity, transitional. The majority of Japanese cars, which New Zealand buys, run on lead-free petrol and this means, as well as health benefits. an improvement in fuel consumption and fewer maintenance costs; these factors, which arg seldom mentioned, would be included in any true cost/.benefit analysis.—Yours, etc., JANET R. HOLM. September 13, 1982.