National Geographic : 1915 Jan
SOME PERSONAL EXPERIENCES WITH EARTHQUAKES BY REAR ADMIRAL L. G. BILLINGS, U. S. NAVY, RETIRED THERE is no natural phenomenon more deeply interesting and yet so little understood as the seismic disturbances which have from earliest history devasted the earth and carried terror and dismay into the hearts of all survivors. Up to 1903, it is computed by an em inent scientist, Compte de Ballore, there had been 159,782 recorded earthquakes. Of later years, when more accurate rec ords have been kept, they have averaged about 60 per annum. There is comfort to the dwellers in most of the world to know that 94 per cent of recorded shocks have occurred in two narrow, well-de fined belts-one called the Mediterranean, with 53 per cent to its credit, and, the other, the Circum-Pacific, with 41 per cent-while the remainder of the world has only 6 per cent, widely distributed. The United States has been singularly free from recorded seismic disturbance, perhaps the most disastrous being in 1811, when a very severe shock occurred in the Mississippi Valley south of the Ohio, which was felt in New York in one direction and in the West Indies in another. This earthquake changed the face of the earth. A vast extent of land was sunk, lakes were formed, and even the course of the Mississippi River was obstructed for a time (see page 67). Most of the earthquakes occurring of late years can hardly be classed with the great ones of history, nearly all of the destruction being caused by uncontrol lable fires. In the more stable zones long periods may elapse between shocks, as, for instance, in Kingston, Jamaica, 215 years intervened. While the Panama Canal is not situ ated in the earthquake zone proper, it has experienced numerous shocks, though none in historic times have been fatal. THE CAUSE Or EARTHQUAKES The cause of earthquakes and vol canoes is an elusive problem, not yet set- tled to the satisfaction of the scientist. Tremors of the earth may be caused by many things. The explosion of mines, falling in of caves, slipping of rock strata, and many other movements of the earth may cause them; but for the great shocks which have recurred almost since the his tory of the world began we must look further. For ages theories have been evolved, and, though most of them have received the earnest consideration of our modern scientists, they seem to be advanced only to be combated and denied; so that, after all, we must confess to the humiliating fact that we know very little about the cause of earthquakes. Though many times there seem to be an intimate connection between earth quakes and volcanoes, the law regarding them has not been established. Some re markable coincidences have been observed in late years. The terrible cataclysm of Mount Pelee, which, on May 8, 1902, al most instantly killed 30,000 inhabitants, was preceded by the earthquake which in January and April of the same year wrecked a number of cities in Mexico and Guatemala. The distance between these points is at least 2,000 miles, showing how deep-seated must have been the dis turbance, if, as has been suggested, there was communication between them. The great San Francisco earthquake was pre ceded only two days by one of the most violent eruptions of Vesuvius recorded in many years. THE BEHAVIOR Or BOGOSLOF It is also a significant fact that the fuming island off the coast of Alaska, called Bogoslof No. 3, appeared at almost the same time. A revenue cutter, visit ing this island, was astonished to see that the mountain, or hill, some 400 feet high, on the island, had disappeared, and in its place a bay had been formed. Soundings showed a depth of from 8 to 25 fathoms of water.