VOLC, 



Indonesian authorities are well aware, 

 the present menace on Kelut is in- 

 creasing as a result of the steady 

 increase of population on the fertile 

 flanks of the volcano. 



In Java, attempts were made to 

 warn of hot mudflows by installing 

 thermal sensors in the upper parts of 

 the valleys on the slopes of volcanoes, 

 with an electrical alarm system in 

 villages on the lower slopes. It was 

 hoped that the villagers would have 

 time to reach high ground before the 

 mudflow arrived. In places, artificial 

 hills were built to serve as refuges. 

 The alarms were unreliable, however, 

 and did not work at all for cool 

 mudflows. 



Mudflows, being essentially streams 

 of water, are closely controlled by 

 topography, and it is possible to an- 

 ticipate which areas are most threat- 

 ened. Dams built to try to contain 

 the mudflows from Kelut failed when 

 the small reservoirs behind them be- 

 came overfull. It might be possible, 

 however, in some favorable localities, 

 to use diversion barriers like those 

 suggested for Hawaiian lava flows. 

 In general, the best possibility seems 

 to be to learn to recognize the situa- 

 tions most likely to lead to mud- 

 flows, and issue warnings when these 

 develop. 



Gases 



The most abundant gas liberated at 

 volcanoes is water. Less abundant 

 are carbon gases, sulfur gases, am- 

 monia, hydrogen, hydrochloric acid, 

 and hydrofluoric acid. Sulfur dioxide 

 and sulfur trioxide unite with water 

 to form sulfurous and sulfuric acids. 



The acid gases may be injurious to 

 plants downwind from the volcano. 

 Mild gas damage resembles smog 

 damage in cities. More severe damage 

 causes fruit to drop and leaves to turn 

 black and fall; it may kill the plant. 

 Serious damage of this sort has been 



experienced on coffee plantations to 

 the lee of the volcanoes Masaya, in 

 Nicaragua, and Irazu, in Costa Rica, 

 and less severe damage has occurred 

 in Hawaii. 



Suggested countermeasures have 

 included trapping the gases at the 

 vents in the volcanic crater and dis- 

 charging them at higher levels in the 

 atmosphere by means of a high flue, 

 or precipitating them by means of 

 chemical reactions. Valuable chemi- 

 cals might be recovered in the process. 

 Local application of chemicals directly 

 on the plants in order to neutralize 

 the acids has been tried, but this is 

 expensive and not wholly effective. 

 Further research on this subject is 

 indicated. 



Predicting Eruptions 



Accurate prediction of time, place, 

 and nature of volcanic eruptions would 

 go far toward eliminating the dis- 

 asters that arise from them. How- 

 ever, although some progress has 

 been made in this direction, we are 

 still a long way from being able to 

 make accurate predictions. The indi- 

 cations that have been used to predict 

 time and place of eruptions are: earth- 

 quakes, swelling of the volcano, 

 change of temperature or volume of 

 gas vents (fumaroles) or hot springs, 

 changes of elevation in areas near 

 the volcano, and opening or closing 

 of cracks in the ground. 



Tumescence — Scientists of the 

 Hawaiian Volcano Observatory have 

 found that Kilauea Volcano swells up 

 before eruptions and shrinks once the 

 eruption has started. However, the 

 tumescence may continue for months, 

 or even years, before eruption finally 

 takes place; furthermore, it sometimes 

 stops and detumescence occurs with- 

 out any eruption. (The magma may 

 be drained away by intrusion into the 

 subsurface structure of the volcano.) 

 Tumescence, therefore, does not indi- 

 cate when an eruption will occur, but 



only that the potential for eruption 

 is present. 



Earthquakes — Some eruptions are 

 preceded by swarms of shallow earth- 

 quakes over periods of a few hours 

 or days. These, combined with the 

 swelling of the volcano, are the most 

 useful short-range tool for prediction. 

 The eruption of Vesuvius in a.d. 79 

 was preceded by ten years of very 

 frequent earthquakes, and with our 

 present knowledge we could probably 

 have made a general long-range pre- 

 diction that the volcano was likely to 

 erupt, though we still probably could 

 not have said just when. Other erup- 

 tions appear to have had no definite 

 seismic prelude. 



Upheavals and Cracks — Marked 

 swellings or upheavals have taken 

 place before eruptions at some vol- 

 canoes, though more commonly none 

 has been detected. This may be partly 

 because of lack of appropriate instru- 

 ments in proper positions. Upheaval 

 of the land causes the shoreline in 

 the vicinity of Naples to shift seaward 

 a few hours or days before some erup- 

 tions of Vesuvius. A similar upheaval 

 preceded the eruption of Monte 

 Nuovo, in the Phlegrean Fields north- 

 west of Naples, in 1538. In 1070 the 

 region was again being upheaved, 

 with the opening of cracks and in- 

 crease of fumarolic action in the 

 nearby crater of Solfatara Volcano; 

 these things suggested strongly that 

 an eruption would take place in the 

 area soon. 



Tilt Tatterns — In 1943, at Showa 

 Shin-Zan, in Japan, the ground sur- 

 face was pushed up to form a bulge 

 150 feet high and 2V2 miles across 

 before the eruption finally started. 

 The 1960 eruption of Manam Vol- 

 cano, near New Guinea, was preceded 

 by a large number of earthquakes 

 and tumescence that resulted in tilting 

 of the ground surface through an 

 angle ranging from 8 to 18 seconds of 

 arc. Tilting of the ground surface has 

 been observed before eruptions at 

 some other volcanoes, but it has not 



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