AN INLAND SEA.

Bush Advocate, Volume XXI, Issue 65, 15 September 1908, Page 8

AN INLAND SEA.

IN THE NORTH ISLAND

The report on the" Tongariro National Park recently presented to Parliament contains a very interesting section, contributed by Mr R. Speight, F.G .S. Discussing the geological history of the district, MiSpeight states tliat the oldest rocks in the neighborhood of the park are the slates and sandstones of the Kaimanawa Mountains. These are probably of carboniferous age, and form a" portion of the structural axis of older rocks which extends through the Nortli Island from near Wellington towards the eastern side of the Bay of Plenty. The southern portion of the.Kaimanawas, at any rate, is 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 or less isolated elevations. At the time of the submergence a great bay or strait must have occupied the middle of the North Island, extending ,nortli-east from Wanganui and probably cutting off the~ submerged parts of the KaiInanawas and Ruahines from islands lying to the north-west. An archipelago then occupied the area now covered by the North Island. Thick h and extensive deposits of marine clays and limestones stretching in a broad band from the Ruahines across, the middle courses of the Rangitikei, ■Wangaehu, and Wanganui rivers towards the Tasman Sea in the west, prove that \n miocene times the sea transgressed over a great area in the south-western part of the island. No doubt, says Mr Speight, a line of weakness in the earth's crust extends in an approximately straight ', line from Ruapehu. through Tonga and Samoa towards distant Hawaii. This line may perhaps be called the "Maori line" of volcanoes, as no doubt the first. Maori immigrants to the country followed its direction more>or less closely, and the legends : of. the native race contain references which sliow clearly that they recognised the linear arrangements of the vents and their common origin. Activity is more pronounced now at the northern end of this line, perhaps owing to the fact that another earthfissure crones it, running west-north-west and east-south-east— i.e., approximately at right angles to the Maori line. The great volcano of Savaii, in Samoa, is placed at their intersection, and hence its continuous activity for the past few years. The Hawaiian line is parallel to the Samoan line, and the Maori line 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 r Speight, that Ruapehu will be active again — perhaps not in the near future, but almost certainly after a long space of time. " .Its general form, the chai'acter of. its lavas, though not in themselves absolutely sufficient to warrant the prediction 'as* certain, yet suggest ■'■that Ruapehn has not passed through, all the phases" of its life-his-tory.

Westerly strong winds to gale soon; rain, probably heavy; rivers rising; glass fall; rivers flooded after 16 hours.