ORIGIN OF THE OCEANS.

New Zealand Herald, Volume LII, Issue 15848, 19 February 1915, Page 7

ORIGIN OF THE OCEANS.

THEORY OF HEAVIER ROCKS. AMERICAN GEOLOGIST'S STUDY. No theory has yet been established that satisfactorily explains the elevation and the depression of the earth's surface into continental masses and ocean depths. A general indication of tfhe present tendency of modern investigation into this subject was given Last evening by Prof, Joseph P; Iddings, who ha;; been for many \ears .1 member of the United States Geological Survey, and is one of the leading authorities on igneous rocks. Prof. Iddings has already spent sis rronths in examining igneous rocks ; n the tiopics. He has been travelling recently in the South Island, and has found an in-

teresting study in the ancient rocks of Port Chalmers and Lyttelton. -®e has still a lengthy programme ahead of him. Prof. Iddings explained that the study of the volcanic rocks of the islands lying in the Pacific has a general bearing upon the origin of the Pacific Ocean. The theory most widely advocated by geologists is ■hat the ocean beds are formed of heavier rocks than the land masses, and an examination of the igneous rocks forming islands that lav: been thrown ip from the depths of the ocean generally supports this 'dea. The author of this view was Archdeacon Pratt, who arrived at the conclusion that the rocks forming the Himalayas are relatively lighter than those in the bed of the Indian Ocean. There appeared to be so many exceptions to his " theory of compensation" that geologists were not greatly impressed bv his arguments. Now, However, there is a strong body of opinion in agreement with the theory, and in recent years, investigations made by the Coast and Geodetic Survey of the United States have supported the view that the American Continent is elevated and the oceans depressed because of the relatively Lighter and heavier rocks. Professor Iddings has been studying the igneous rocks m the light of this theory. Siid has found that th'*e originating in tile floor of the ocean displav a greater density than those ejected from the land masses. His purpose in coming to New Zealand ha.-; been to collect additional evidence, and to make the acquaintance of such investigators as Dr. Marshall and Mr. P. Speight, curator of the Canterbury "Museum. Dr. Marshall has come with him to Auckland, and will accompany him nurip" his tour of the volcanic regions, including the Rotorua district.