AH ANCIENT SEA.

Gisborne Times, Volume XXVI, Issue 2298, 17 September 1908, Page 1

AH ANCIENT SEA.

IN THE NORTH ISLAND. The report oil the Tonga riro National Park presented to Parliament lust week contains a very interesting section, contributed by Air It. Speight, F.G.S. Discussing tlio geological history of the district, Air Speight states thatthe oldest rocks m tho neighborhood of tlie park are the slates and sandstones of the Kaimunawa Mountains. These are probably of carboniferous age, and form a portion of the structural axis of older rocks which extends through Die North Island from near Wellington towards the eastern side of the Bay of Plenty. The southern portion of the Kaimanawas, at any rate, as part of a plain of marine denudation formed in tertiary times, and the tolerably level surface then acquired was subsequently raised above sea-level and thoroughly dissected by stream-action, so that now it is composed of a number of more o;' less isolated elevations. ■ At the time of the submergence a great bay or strait must have occupied the middle of the North Island, extending north-east from Wanganui and probably cutting off the unsubmerged parts of the Kaimanawas and Rualiines from islands lying to the-north-west. An archipelago then occupied the area now covered by the North Island. Thick and extensive deposits of marine clays and limestones, stretcfliing in a broad band from the Ruahines across the middle courses of the Kangitikei, Wangaehu, and AVungaliui Rivers towards the Tasman Sea in the west, prove that in niioceiio times tho sea transgressed over a groat area in the south-western part of the Island.

No doubt, says Air Speight, a line of weakness in tho earth’s crust extends in an approximately straight lino from Ruapehu through Tonga and Samoa towards distant Hawaii. Tins line may perhaps bo called tho “-Maori line” of volcanoes, as no doubt tho first Alaori immigrants to tho country followed its direction lnore or less closely, and tho legends of tile Native race contain references which show clearly that they recognised the linear arrangement, of tlio vents and their common origin. Activity is more pronounced now at tile northern end of this line, perhaps owing to the fact that another earthfissure crosses it, Tunning west-iiortfli-west and east-south-east —i.e., approximately at right angles to the Alaori lino. The great volcano of Savaii, in Samoa, ig placed at their intersection, and lienee its continuous activity for tlie past few years. The Hawaiian line as parallel to the Samoan line, atid the Alaori lino when prolonged intersects it .at the centre of its greatest activity. There are thus two intersecting sets of telluric cracks crossing the Pacific Ocean. It is likely, thinks Mr Speight, that Ruapehu will bo active again—perhaps not in the near future, but almost certainly after a long space of timo. Its general form, the character of its lavas, though not in themselves absolutely sufficient to warrant tho prediction as certain, yet suggest that Ruapehu has not passed through all the phases of its life-liis-tory.