THE CHARACTER OF THE OCTOBER STORM OF DUST.

Star (Christchurch), Issue 18643, 24 December 1928, Page 10

THE CHARACTER OF THE OCTOBER STORM OF DUST.

NOVEL ASPECTS DEALT WITH BY SCIENTISTS. (Special to the “Star.”) WELLINGTON, December 24. October’s dust storm which visited the Dominion, although not unique, was of sufficient interest to be worth scientific investigation. This has been done by the Department of Scientific and Industrial Research, a comprehensive report having been prepared on the phenomenon. Such a dust storm, it is pointed out, is a very unusual occurrence, the last previous occasion when such a fall was observed and recorded being on November 14, 1902. The dust on that occasion, as in October’s storm, was shown conclusively to be of Australian origin. The fall of last October was far heavier and more widespread than that of 1902. All samples of dust collected and forwarded for analysis had in appearance the same yellowish red or buff colour, which gave the distinctive colour to the clouds and to the surfaces on to which the dust fell. When examined microscopically, the largest particles were found to have a diameter of 0.508 mm., but these were very exceptional and flaky. There were few particles larger than 0.04 mm. The minerals which could be distinguished were flakes of mica and abundant, well rounded grains of quartz, a certain amount, of organic matter being also present. Chemical analyses of the dust of both falls gives much the same result. It is similar to the red clay found over a large area on the bed of the southern Tasman Sea, it being supposed that the deposit is really composed of dust blown from the Australian continent. Dr Marshall estimates that October’s dust storm fell over an area of at least 10,000 square miles, the total deposit being approximately 100,000 tons. Dr Kidson enters in detail into the meteorological conditions prevailing before and at the time of the dust storm, showing that the conditions over Australia were favourable for the raising to high altitudes of vast quantities of dust which would be carried in the direction of New Zealand. The thunder storms experienced in the Dominion at the time of the storm, which were in many cases exceptionally severe. Dr Kidson says, were almost certainly associated with the presence of dust in the atmosphere. Dr Kidson estimates the total deposit in New Zealand at between 50,000 and 100,000 tons, one of the most striking features being the chocolate or pink snow which fell in Otago. “A remarkable feature of the phe-

nomenon,” he concludes, “is that the dust should have been so long concen- ’ trated in the atmosphere after such a long journey. The average distance tra- ' veiled by the time New Zealand was reached must have been at least 2000 ; miles. The speed probably varied be- : tween 25 and 60 miles an hour.” The writer is of opinion that South and . Central Australia must have supplied their quota to the total dust content, in addition to Queensland and New ; South Wales, and that the high degree : of saturation could only have been reached by the atmosphere receiving additional supplies during the course of ( several davs. The transport of the . dust over long distances is frequently recorded, but such a striking instance as the present had not previously come under the writer's notice.