'LIVE MOUNTAINS.

Waikato Times, Volume 97, Issue 15270, 21 June 1923, Page 7

'LIVE MOUNTAINS.

SOURCE OF EARTHQUAKES. "Live mountains" are said by Professor Bailey Willis, oC Stanford University, to be the cause of the most serious earthquakes. On the Atlantic : coast of the United States the moun- ! tains, he says, writing in the Daily Science News Bulletin (Washington), are dead, but on the Pacific coast, and in a great belt stretching across Asia and the Mediterranean, the mountains are "growing," owing to the pressure set up by the shrinking of the earth's surface. "This," he writes, "is the modern theory of earthquakes. It was developed through the studies' of the great earthquake of 190 G, which caused the Are that destroyed San Francisco, and it has been demonstrated since by observation of many minor earthquakes and by a. study of the lines ! along whicluthey occur. "Wc often speak of an earthquake plane as a fracture, but it is not really a break. It is the surface between two great masses which never have been united, but which for ages have been slipping past each other; and where this plane comes out to the surface of the earth we have a line which is sometimes called an earthquake rift. The greatest of these rifts, so far as it is known, in the United Stales extends through the coast ranges of California for a distance of 000 miles. It passes just west of San Francisco, to the cast of Los Angeles, and disappears in the Gulf of California. Along the San Andreas rift, as it is c-alled, earthquakes have occurred at different times in different sections; the most recent was the 'quake of 190 G, which covered a stretch of 150 miles, with San Francisco near the centre. South of that stretch for some 300 miles there has been no movement since 1857, Avhcn there was a severe shock, the marks of which may be traced across the desert plains like an irrigation ditch. Still further south there have been several recent shocks, but none of great violence, although there is evidence of considerable activity in the section east and south of Los Angeles. Earthquake Rifts. "In view of the fact that We can thus locate certain linos along which earthquakes have occurred, we are able to speak of live earthquake rifts as wc speak of live volcanoes. We know by the form of the volcano or by the occurrence of the eruptions , within historical time that it is poten- ! lially or actually active, and much the same may be said of earthquake rifts. There arc lines of special danger on which no dam or sohoolhouse or skyscraper should be erected. They should also be avoided, as far as pos- i sible by railroad lines, bridges, aque- j ducts, and other publ'o works, and yet it, happens that they often run through | valleys where such work is suggested j by the conditions of the ground. As j long as wc remain ignorant of their position, we vun the risk of inviting destruction, but it is not difficult by proper studies to indicate the lines of danger on a map and to make the information public for the benefit of engineers and others. 1

"Thus it happens that a map of California showing the lines of active earthquake rifts and also of faults that are believed to be inactive is about to be published by the Seismological Society of America as a result of work carried out in co-operation with the Advisory Committee in Seismology of the Carnegie Institution of Washington. It is, however, but one item in the programme of that Committee, which embraces pjans for the investigation of earthquakes in many relations. "It may perhaps be asked of what use is it to study a phenomenon which is as sure and as inevitable as an eclipse of the .ruii. Since we cannot stop it and probably cannot predict it with certainly, what practical benefit can we hope to derive from an investigation of it? There is, of course, the answer that we wisli to know; we wish to understand our earth and all its manifestations; but apart from that, as has already been pointed out, the lines along which earthquakes are likely to occur and arc most dangerous may be determined, and it seems not impossible that if we can perfect our knowledge wo may be able to devise methods of forestalling their disastrous effects "by the selection of safer sites or by appropriate methods of construction. It is clearly recognised, for instance, that the destruction of San Francisco was in large measure due to the fact that its principal aqueduct followed the earthquake rift for many miles, whereas now it has been built along a mountain range which, if it moves, will move as a block and will not dislocate the uiDc-line."