EARTH’S HEART

Gisborne Times, Volume LXXXVI, Issue 13092, 13 February 1937, Page 5

EARTH’S HEART

AT DEPTH OF 300 MILES

THE PLANETS COMPARED While the planets Mars and Mercury appeared to have negligible metallic cores, that of Venus resembled the ccro of the earth, said Mr. K. E. Bullen, of the Auckland University College, presenting a paper before the Australian and New Zealand Association for the Advancement of Science-’. He was speaking of the constitution of the earth and certain of the planets. For some time it had been known that there was a sudden change of material below the earth’s surface at a depth equal to about half the earth’s radius, Mr. Bullen said. On the upper side was a solid material commonly referred to as the earth's shell, and below a dense metallic core, probably liquid. There were also verious discontinuities in the crustal layers of the> earth extending to a depth of about 23 miles. Mr. Bullen said a joint research by Dr. Harold Jeffreys, F.R.S., and himself at Cambridge in 1933 revealed tho existence of a new discontinuity at a depth of 300 miles. The results indicated also that there were probably no further marked discontinuities in the shell. Since then, Mr. Bullen said, he had obtained a solution of the variations of density and pressure inside the earth. They both gave independent evidence of tho existence of the new discontinuity and also supplied an evaluation of tho jump in density there 3.69 to 4.23). “The question has to be taken up by Dr. Barnal, of England, who is using this result and saint further researches of Dr. Jeffreys on tho velocities of seismic waves near the discontinuity has put forward a plausible hypothesis regarding its cause. '

“It appears,” Mr. Bullen said, “that the- change of property is essentially one of molecular structure directly due to the high pressure, there being no essential chemical difference between tho materials below and above discontinuity.”

A further consequence of the solution secured by Mr. Bullen was that the earth’s central core appeared to consist almost wholly of iron, whereas previous tentative solutions had suggested the presence of substantial quantities of heavier metal. “Subject to certain hypotheses on probable similarities in the constitutions of the various planets, the nejv solution for the earth makes it I>-V----siblo to estimate, tho sizes of the metallic cores in some of the planets,” the paper added.