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Poverty Bay Herald, Volume XXXIII, Issue 10692, 16 May 1906, Page 3

Dr P. Marshall, for his opening address as President of the Olago Institute lust Tucsduv evening, gave am interesting lecture oii the history of volcanic action m Now Zealand. One of the moj-t curious things about the must volcanic activity m tliese islands, is the existence of over 60 tiny volcanoes, within a comparatively small area hi tlie neighborhood of Auckland. Dr Marshall offered an explanation that appears to fit thc facts. The largest of the Auckland volcanic cones is Rangy toto the northernmost, and the lava rock that issued at this point is of thc same nature as that of Pirongia. near Kawhia, 70 or' Bo miles away. This similarity of tho molten rock suggested that an "intrusive sheet of lava wos forced between sedimentary strata at no great depth beneath the surface, as far as Auckland. (Intrusive sheets of 6uch length are known elsewliere. The Palisades of the Hudson, above New York, are tho exposed section of an intrusive sheet over 80 miles long, so far as it is visible.) The Pirongia sheet on reaching the neighborhood of Auckland encountered wet strata, and converting the water into steam, it set up a number of small explosion volcanoes. Going further on, the molten rock itself came to the surface m Rangitoto.