The Nuée Ardentes of Sabalan Volcano in Iran

摘要

This article deals with the introduction and explanation of the two nuéeardentes of “Mue’el Valley” and “Shirvandareh Valley” which are one type of the pyroclastic flows of Sabalan volcano. One of the features of nuéeardente in these two valleys is the presence of large blocks in upstream of valley and the abundance of ash in downstream which it has happened in one stage in Mue’el and in several stages in Shirvandareh Valley. Considering the antiquity of the great Sabalan volcano and numerous changes that have happened during these long years in the region, determining the temperature of nuéeardente was impossible. But what could be mentioned as a sign of high temperature because of nuéeardente is the presence of rust ground mass on piece levels which indicate hot water steam (500°C to 600°C). Also puzzle breakings like those in these rocks should be the result of severe explosion blast and very fast movements of nuéeardente that has broken these rocks instantly. These nuéeardentes are peléan type and they are more or less synchronous, and the main reason could be the huge explosion which happened because of the second caldra’s subsidence. By comparing deposits of the two nuéeardentes of Mue’el Valley and Shirvandareh Valley, it is observed that the extent, thickness, and size of blocks are higher in Shirvandareh than those in Mue’el Valley. Also considering higher levels of pieces’ adherence and hardness of deposits, it can be concluded that the temperature of this complex was higher than that of Mue’el Valley, and in general the power of Shirvandareh’s nuéeardente is more than the Mue’el Valley’s.