VOLCANIC ERUPTIONS

Taranaki Central Press, Volume IV, Issue 454, 23 June 1937, Page 2

VOLCANIC ERUPTIONS

CAUSED BY HEAT AND GAS ! Influence Of Radium In Earth Sydney, June 2. ! A theory that volcanic eruptions are caused by the heart radiated by the radium in the earth has gained some credence among scientists, Professor L. A. Cotton, professor of geo- I logy in the University of Sydney, j said when commenting on the eruptions at Rabaul. • “Volcanic eruptions are caused by ' an of heat, or an accu- , mulation of gas pressure breaking through a weakness in (the earth’s crust,” Professor Cotton said. “What causes an accumulation of gas pressure is not exactly known, but it seems to be the result of some deepseated disturbance under the surface of the earth. “The accumulation of heat may be a consequence of the accumulation ■ of pressure, but an alternative the- j ory enunciated by Professor Joly is ■ that the heat associated with volca- i nic eruptions is the heat radiated by ’ the radium in the earth. Radium is j found, in minute qualities, in all vol- i canic rocks, and for this, and other i reasons, Profes.sor Joly holds thait j the radium in the earth is the direct | cause of many eruptions. His the- : ory has gained ground recently, al- ; though, of course, it still remains a ! theory.”

Gas Pressure. Professor Cotton said that no one could say precisely why a volcano erupted. At Rabaul it appeared thait gases at a high pressure accumulated near the junction of the two great world volcanic belts. The pressure of these gases became greater and greater until they caused minor earth tremors, which probably would have indicated to a trained seismologist that /the earth’s crust was becoming progressively more unstable. Finally the pressure became so great thait the gas was able to break through /the weakest point in the crust, and this breaking through was what was called “the eruption.” Usually the gas or molten rock broke through at a point which nad been weakened by previous eruptions. This apparently was what had happened at Rabaul. It did not seem, however, that there had been any flow of lava. This was not unusual. The old theory that the earth under its crust consisted of molten rock had been abandoned by geologists. The modern theory was that the earth wa £ generally quite solid. At isolated places the underlying rocks might melt, for reasons not properly understood. When this happener, and when at 'the same time, the forces generated by heat or pressure broke through the earth’s, crust, an eruption which was accompanied by the flow of lava, or molten rocks, would take place. Forecast Correct. Professor Cotton said that it was not impossible for a seismologist to predict an eruption. A striking example of this occurred in Japan in 1914. One of the leading scientists

I of that period, Professor Omori, was j studying the volcanic mountain, Sa- ■ kurajima. From his observations • he found the conclusion that a vio- ! lent eruption was likely to take place, i and he communicated with his Government and advised them to move I residents from the island on which 'i the mountain stood. i The advice was taken and the vil- | lagers were removed to the mainI land . Two weeks later Sakurajima i j erupted violently, and did great J damage to farm land. The streams I of la va were, so large thait they join- • pd the island to the mainland. >“lt is probable,” Professor Cotton said, “that Profesor Omori made his prediction because he observed that I the tremors which are common in j volcanic regions were increasing in i intensity and occurring ait shorter I intervals. It is also probable that, i had a seismologist been at Rabaul, !he would have observed that ithe I earth tremors, which are common > there, were growing more serious, and he might have been able to predict the eruption which has actually occurred. “These tremors indicate 'that the I earth’s crust is unstable, and when I they increase in intensity, or occur I at shorter intervals, it is a plain inj dication that the instability is growl ing more marked, and that the cause ! is an accumulation of heat or presI sure.”