UNSTABLE BED OF PACIFIC

Taranaki Daily News, 12 February 1931, Page 7

UNSTABLE BED OF PACIFIC

THRUSTING UP MOUNTAIN POSSIBLE CAUSE OF EARTHQUAKE. THE theory of professor see. The activity in the ocean bed of the Pacific and the theory of its relation to the recent earthquake at. Hawke s Bay were outlined to a News reporter by a student of geology, at New Plymouth last evening. Forming as it were the back-bone or New Zealand, he said, there were two ■axes. The first axis began from Mt. Aspiring at the end of South Canterbury and ran in a north-east direction through the South Island, continuing on through Wellington to the East Cape. The other ran from Taupo in a northwest direction, disappeared in the sea near the Three Kings and cropped up again at New Caledonia. Both these axes were bound by great oceanic depths. Along the ridge or axis going to New Caledonia the water was less than 1000 fathoms and in some parts 500 fathoms, while the water on each side went down in some cases to 2000 fathoms. The deep in the Tasman was called the Thomson Deep. Extending out from East Cape was the great depth called the Aldrich Deep, which went down to 5000 fathoms. When one added to that the fact that the Pacific was still in the process of sinking it was natural that there should be great stresses along the edges of the deeps, particularly of the Aldrich Deep. NEW ZEALAND ON RIDGE. “New Zealand is essentially in the position of a ridge lifted by stresses above sea level,” he said, “just as are the other islands in the Pacific. With the further settling down of the Pacific New Zealand is given a sharp tilt up and it is natural that there should be a rise in the sea floor on the Napier coast. Faulting in the past as far .as is known has occurred about 300. yiiles south-east *bf Hawke’s Bay. This one must have been relatively close to Napier.” ... There were other fault lines associated with the physical structure of the country. A fault line rau from the neighbourhood of Wanganui to East Cape, intersecting the major fault. That was possibly the line which gave Wanganui and Taranaki their shakes. Another region of minor adjustment, a region of. structural insecurity, was off Kawhia. In Otago there were any number of evidences of reednt faulting. The structural axis of Otago ran at right angles to the main axis. It ( had been stated that the cause of the faults was the gradual shrinkage of the.earth’s crust, but there was no reason, with what was now known of radio activity, to suggest that. Professor See’s view, cabled from San Francisco, was that the earthquake was caused by movements in the ocean floor. SUBMARINE MOUNTAIN RANGE. The theory of Professor See was that the great earthquakes occurring in the Pacific were developing a high submarine mountain range of which only a few peaks rose above the water. The most active region of seismic disturbances was along the Aleutian, Kurile and Japanese Islands and in the East Indies. Along the Aleutian Islands the sea-bot-tom was sunk down into a narrow trough which for a considerable distance was over 4000 fathoms deep and exactly parallel to the chain of islands. The chain of islands were merely the highest peaks of a mountain range rising parallel to the deep trough. It was calculated that if the elevation of that range were shovelled off and thrown into the trough it would just about fill the depression and leave the surrounding sea bottom of nearly uniform depth. After great earthquakes in the Pacific region new islands were frequently raised from the sea and several new volcanoes had broken out within historical time. Seismic sea waves frequently followed, the water first withdrawing from the range of islands to the trough in the south and then returning later as a great wave. That showed that the sea bottom sank after, the earthquakes. As the islands and the submarine mountains were uplifted by the disturbance and the sea bottom afterwards sank, it was evident that lava was expelled from beneath the trough and pushed under the adjacent range. In this way the lava expelled from the trough off the coast of Hawke’s Bay, according to Professor See, had been forced up under the range or axis which passed in a northwesterly direction through Hastings and Napier. Even at the present time, according to Professor See, the formation of islands, mountains and borders of continents Was still going on. Not only was mountain formation and the uplift of islands progressing near the margins of the sea but also at a considerable distance from the continents towards the interior of certain oceans. A ridge built up by the injection of lava was being formed in the regions of tho Friendly Islands in the Pacific between Samoa and New Zealand. He held that the Pacific was there developing a long mountain wall on the west which would eventually connect Samoa and New Zealand. From a similai' process North America would eventually be connected with Asia and the Arctic would be entirely cut off from the Pacific Ocean.