The Guardian And Evening Star, with which is incorporated the West Coast Times. WEDNESDAY, SEPTEMBER 30, 1925. EARTHQUAKE CAUSES.

Hokitika Guardian, 30 September 1925, Page 2

The Guardian And Evening Star, with which is incorporated the West Coast Times. WEDNESDAY, SEPTEMBER 30, 1925. EARTHQUAKE CAUSES.

AccoitmNt; to Science Service, the relent .severe earthquakes leit in Calii'oniiii and Montana, and tin; mountain .slide in Wyoming, have aroused intirest in the theory of Professor .1. Jolly, English geologist. on radioactivity, as the possible cause of quakes. It is a well-known fact that throughout the entire earth’s crust minute quantities of radioactive elements exist, mainly thorium and uranium, which are con. stantly producing heat by breaking down at a rate quite independent of the pressure and temperature found in the outer parts of the earth. Thu granites which arc in the outer layer of the mirth's ( rust contain approximately three times as much of these radioactive elements as the basaltic layer, which is deeper, and this latter is twice as rich as the denser and more basic layer of peridntites. Continents are essentially composed of granite embedded in a suit-stratum of basaltic composition. This has a lower melting point than the granite and increases in volume about ten per cent. at its melting temperature. And since the haCaltic layer i- self-healing, due twits radioactivity. Professor July states that it lacks only the latent heat <;i fusion to become llttid. and further that at the present rate of disintegration it must again become fluid in about .‘U millions years. When this expansion has reached its greatest point the surface crust is correspondingly raised, and increased in area about 0-50,000 square miles. The stir lace tension l>eromes so great that eon tinentsand ocean floors are split apart. Tidal action starts a slow westerly drift of die still solid continents, and the superheated substratum which originally lay beneath a continent now comes to lie beneath the ocean floor, which melts away from below until the increasing rapid loss of heat from the iv.can cheeks and finally ends the process. The reverse action now begins. Crystallisation in the liquid balsa It ie layer takes place, the vastly increased land aiea contracts, and settles down into the solidifying substratum, and the margins of the continents especially are market] by intense

compression, producing immense depression and upheavals. This in brief is the cycle whereby the excessive heat due to radioactivity is accumulated and lost, during whi' h succeeding cycles the ancient Eurasian ranges and the fairly recent Himalayas and l’acil'rrange.- have been thrown up during the different geologit epochs. That such a cycle is nearing completion in the l'aeifi ■ region is known, dne to current, observations on the steady sinking of the ocean floor and the regularity of the tremblers, most of which are so slight as to he recorded only hv the seismograph, hut which occur regularly every 10 or Id minutes. AA'hcn asked for his opinion of (hi- idea of the origin of earthquakes Commander X. If. fleck, chief of the Division of Terrestrial Magnetism and Seismology of the I’.fs. Coast, and Condo! ie Survey, stated : “It is of course, only one of the hypotheses that have been advanced to explain earthquakes. I do not feel that we are yet in a position t-

place it great amount of weight in any of them, that is as to the actual cause of the earthquake. We know pretty well how an earthquake occurs, hut it is not yet certain which of the several hypotheses that have lieeu advanced I lost accounts for the stresses wbh h causes the earthquake. It. is quite possible that a number of different element-, such as the processes of erosion and deposition, the radioactivity, as mentioned, and oilier causes within the earth, work together to produce the stress, while the trigger forces that -et oil' the earthquake may come either from within or from without the earth."