Tongan Eruptions

Meteorologists Evacuate

Raoul Island

Tongan Eruptions May Follow Series In Kermadecs

The western islands of Tonga >uld be the scene of spectacular

)lcanic activity soon because

icy are on a line of weakness in ie earth’s crust where greatly in eased volcanic activity has

jen experienced recently.

line of weakness runs from Mt. Ruapehu in the North and of New Zealand, through hite Island in the Bay of Plenty, rough the Kermadecs about 600 iles north-east of Auckland, and rough the Tongan islands of Ata, jnga Tonga, Hunga Ha’apai, ikon (Fonuafo’ou), Tofua, Kao, te and Fonualei to Savaii (West i Samoa).

Increased volcanic activity along s fault line has resulted in: • Earth tremors at the rate of out 30 a day being felt on Raoul and in the Kermadecs from wernber 10. About 10 days later, ; crater lakes on Raoul began ipting, and it was deemed advisable evacuate the nine-man team of w Zealand meteorologists stationed ;re. • Earth tremors in Tonga in ivember. • Earth tremors in Apia, Western moa, on November 11, 12 and 16.

Lhe Lecturer in Geophysics at the Jney University, Dr. A. A. Day, d PIM that the violent activity the Kermadecs “could well :sage the reopening of the fault e fissure further north,” parti arly as volcanic activity in this :a had been very low in recent irs. rhis could produce “a series of bursts northwards along the canic chain running through nga in the next few years.”

Submarine Volcano \ few weeks before the tremors Raoul Island began a lively sub rine volcano was discovered ween White Island (Bay of nty) and the Kermadecs. The cano is about 200 miles from ckland.

According to existing charts, the

seabed in this area is featureless, with a constant depth of 150 fathoms.

But Dr. A. C. Kibblewhite, deputy director of the Naval Research Laboratory in Auckland, said in early November that investigation by the New Zealand research ship Tui had revealed the presence of a lively under-sea volcano a mile high and about 10 miles long.

The underwater mountain ap peared to be the centre of a major region of volcanic activity along a ridge extending from Raoul Island in the Kermadecs to White Island, where there was continual volcanic activity.

A New Zealand Government vulcanologist, Mr. J. Healy, who flew from Auckland on November 21 to make an aerial inspection of volcanic activity at Raoul Island, reported that he was sure further activity would be experienced, but it would probably not be big.

However, the risk of leaving the weather staff there was not justified, particularly as the settlement was vulnerable.

Following this survey, the nine meteorologists on the island took shelter for the night on board HMNZS Lachlan in case the island began erupting during darkness.

The Lachlan had arrived at Raoul a short time earlier with a party of 13 ornithologists to study the island’s bird life, and another vulcanologist, Mr. E. Lloyd. The ornithologists’ visit was to mark the 25th anniver sary of the Ornithological Society of New Zealand ( PIM, Aug. p. 23).

Mr. Lloyd landed on the island on November 21 with a reconnaissance party, and after spending most of the day on the island, he recom mended that it should be evacuated for several weeks while developments were observed.

Mr. Lloyd reported that black smoke and steam were rising inter

mittently from the island’s green and blue crater lakes, and that the water in the green lake had risen 10 to 11 ft the previous day.

The level of the blue crater lake, the main one, had also started to rise, and a few hot springs had been observed at its side. This lake was rising about one inch an hour, and the bottom of the lake was ap parently being elevated.

On November 22, a report from the Lachlan said that debris had been hurled 2,000 ft into the air from the green crater lake that morning, and that an investigating party had been driven away from the blue lake by an eruption which hurled debris 500 ft into the air.

According to New Zealand reports, the last “full-scale eruption” at Raoul Island occurred in 1872, but several eruptions and earthquakes have been recorded there over the past century.

On several occasions during the century settlers have been driven away by the violence of volcanic activity. However, one family, the Bells, put up with Raoul’s disturbing conditions for 36 years—from 1878 to 1914.

Notoriously Unstable

The islands in Tonga which may suffer a chain reaction from the latest Raoul Island eruptions are notoriously unstable.

One of the islands, Falcon, which is at present submerged, is some times called Jack-in-the-Box because of its appearances and disappear ances.

Falcon was first reported as a shoal by HMS Falcon in 1867. Ten years later, another British naval vessel saw smoke rising from the spot; and in 1885 a volcanic island rose from the sea, two miles long and 250 ft high.

During the next few years, the island was rapidly eroded by the sea, and in 1898, it was reported to be only a reef, barely awash. It re emerged slightly in April, 1900, but by 1913 it had disappeared altogether.

It erupted again in October, 1927, and in May, 1928, when it was about two miles across, the Tongan Govern ment annexed it. As on the previous occasion, the sea gradually eroded it, and by early 1959 it was again submerged. It has not reappeared since.