Emplacement temperatures of the November 22, 1994 nuee ardente deposits, Merapi Volcano, Java']Java

A study of emplacement temperatures was carried out fur the largest of the 22 November 1993 nuee ardente deposits at Merapi Volcano. based mainly on the response of plastic and woody materials subjected to the hot pyroclastic current and the deposits, and to some extent on eyewitness observations. The study emphasizes the Turgo-Kaliurang area in the distal part of the area affected by the nuee ardente, where nearly 100 casualties occurred. The term nuee ardente as used here includes channeled block-and-ash Rows, and associated ash-clouds of surge and fallout origins. The emplacement temperature of the 8 m thick channeled block-and-ash deposit was relatively high, similar to 550 degrees C, based mainly on eyewitness reports of visual thermal radiance. Emplacement temperatures for ash-cloud deposits a few cm thick were deduced from polymer objects collected at Turgo and Kaliurang. Most polymers do not display a sharp melting range, but polyethylene terephthalate used in water bottles melts between 245 and 265 degrees C, and parts of the bottles that had been deformed during fabrication molding turn a milky color at 200 degrees C. The experimental evidence suggests that deposits in the Turgo area briefly achieved a maximum temperature near 300 degrees C, whereas those near Kaliurang were <200 degrees C. Maximum ash deposit temperatures occurred in fallout with a local source in the channeled block-and-ash Row of the Boyong river valley; the surge deposit was cooler (similar to 180 degrees C) due to entrainment of cool air and soils, and tree singe-zone temperatures were around 100 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.