STUDYING VOLCANOES.

Sun (Christchurch), Volume VII, Issue 2127, 8 December 1920, Page 12

STUDYING VOLCANOES.

IMPORTANT WORK IN HAWAII. DR ALLAN THOMSON'S REPORT. Dr J. Allan' Thomson (Director of the Dominion Museum) has returned from Honolulu, where ho and Dr C. Chilton (Christchurch) represented New Zealand at the Pan-Pacific Science Congress. He was able to give much attention while in Hawaii to the study of volcauology. He visited the observatory there, as the guest of Dr T. A. Jaggar, and spent about a month studying the methods employed, and in visiting the different islands and craters of the group, before returning to New Zealand, via Samoa. Dr Jaggar, while on a visit to New Zealand in May, supplied to the Government a report on the question of establishing an observatory and a Department of Volcanic Research. The crater of Kilauea, says Dr Thomson, is a great pit about three miles long by two miles wide, with walls, roughly, 500 ft high. The bottom is filled with recent lava flows, which have isBued from a smaller pit, Halemaumau, Within the greater. This pit is of a variable depth, and its bottom is occuj pied by crags and lava lakes. Both crags and lakes rise and fall, generally very slowly, so that sometimes the pit is 600 ft deep and sometimes has no depth at all, and the lava then flows over the brim into Kilauea. At the time of his visit, the pit was about 250 ft deep, and was sinking a few feet each week. There ■were then three lava lakes, and the lava was in constant motion. The largest lake was three-armed, and the lava flowed from a point on one side of the three arms. A dark skin covered the surface of the lava, but this continually cracked over the flow, and a constant succession of fiery hieroglyphic figures appeared. Again, when the flow impigned on points on the pit sides or on Email islands, the lava rose in fountains six to 10 feet high. It was always necesBary to move to tho windward side of the pit, as the steam and sulphur on the leeward side were very irritating, besides obscuring the view. The scene was more impressive in its weirdness at night, when the orange-red of the cracks and fountains was intensified, and the Bteam and sulphur clouds glowed violet red from tho reflection from the lava . flow. The rise and fall of the lava column have been measured twice weekly for nine years by Dr Jaggar and his assistants, and during that time records have been kept of the minor earthquakes, the "tilts," and micro-tremors, and it has been found that the movements of the lava column can be corrected with the very complex earth movements due to the "solid tide" upon the earth caused by the sun and moon and that the rises are always preceded by a "tilting" at the obsorvatory about 18 days earlier. As the earth tides can be predicted, it has now become possible to predict the rise and fall of the lava column, and sudden rises can be predicted 18 days ahead by the "tilting." The eruption of Maunaloa, a neighbouring but much larger volcano, whose lava column is obviously in close connection with that of Kilauea, and a simultanous eruption of Kilauea during last year were successfully predicted by Dr Jaggar. The areas covered by the Hawaiian lava flow are fortunately not at all closely populated, being mostly given up to cattle ranching, but it can be Been, said Dr Thomson, how important Buch predictions would be in a closely- . populated area. The most successful case of prediction was that of the eruption of the volcano of Sakura-jima, on an island of the same name off tire south-western coast of Japan, in 1914, by Professor Omori, the chief earth- \ quake authority of Japan. Only two weeks' notice of this eruption was given, but such was the confidence of the Japanese Government in Professor ! Omori's work that all people were taken off the island and the population of the neighbouring coast voluntarily I emigrated. A fortnight later the island blew practically to pieces, but not a single life was lost. New Zealand's volcano district .extends from Ruapehu to White Island, and on that line the disastrous Tarawera eruption, the eruptions of Waimangu and White Island and lesser disturbances, especially those of Ngauruhoe, all occurred. "Great volcanic disturbances must be anticipated in that belt at long intervals," said Dr Thomson, "and surely it is worth the serious consideration of the people of New Zealand whether a form of insurance should- not be prepared in the chape of a volcanic observatory, which, after a few years' 6tudy of conditions, could issue successful predictions both • of the place and time of eruptions."