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National Geographic : 1902 Dec
Contents
ERUPTIONS ON MARTINIQUE AND ST VINCENT Boys Carrying Water to Refugee Camp, Georgetown, St Vincent, May 27, 1902 bombs answering this description have as yet been reported as occurring on Martinique or St Vincent. The near est approach to a characteristic bomb are certain rudely spherical masses of lava with cracked surfaces and without projections or indications of a spiral twist. Evidently these poorly shaped bombs are composed of fresh lava which was sufficiently hot to make it some what plastic at the time it was blown into the air, but was too rigid to acquire the typical shape frequently to be seen in large numbers of bombs about cer tain basaltic craters. The absence of characteristic bombs on Martinique and St Vincent is in keeping with the composition of the lava thrown out. The fresh lava is an andesite having in a gen eral way the composition of a refrac tory brick, and unless very highly heated would not be plastic. The dark color of the columns of steam rolling up from the craters when in violent eruption and the vast quantities of fragmental material showered on the adjacent land and sea is evidence that as molten rock was forced up the vol canic conduits it became cooled and stiffened before reaching the summits of the volcanoes, and was shattered by steam explosions and the fragments blown into the air. Not only are true volcanic bombs absent, but clots and splashes of plastic or fluid rocks, such as are common about many volcanoes that have erupted easily fusible material, are also lacking. The fragments ejected were in many instances blown to a height of many thousands of feet, the finer lapilli and dust being carried perhaps five or six miles high, and on falling were distrib uted in part through the influence of the winds, in a general way in reference to size and weight. The larger and heavier masses fell near the craters from which they were projected, while much of the finer and lighter material was car ried great distances. Variations in the method of distribution were caused by the direction of the hurricane-like blasts which swept down from both Mont Pelee and La Soufriere during their mightier eruptions, by the direction of the trade winds and upper air currents, and by tornado-like swirls in the greatly disturbed atmosphere. The vastness of the area on which the ejected material fell is indicated by the fall of dust on Barbados, Trinidad, and on ships 275 miles southeast of St Vincent. Observations reported by E. O. Hovey show that, contrary to earlier accounts, written in part by myself, coarse material fell in St Pierre. The riddling of boiler plates one-fourth inch thick, in the northern portion of the stricken city, by stone shot against them from Mont Pelee, is evidence that the hurricanes of steam charged with hot dust, which swept down from that volcano on May 8 or May 20, and perhaps during later eruptions, were accompanied by a bom bardment of stones, no doubt hot, which were as deadly as solid shot fired from a cannon. Causes of Death.-Respectingthe gen eral cause of death in St Pierre, the re ports of various observers differ more widely than in connection with any 425
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