Nuees ardentes of 22 November 1994 at Merapi volcano, Java, Indonesia

Nudes ardentes associated with dome collapse on 22 November 1993, at Merapi volcano traveled to the south-southwest as far as 6.5 km, and collectively accumulated roughly 2.5-3 million cubic meters of deposits. The damaged ar ea comprises 9.5 km(2) and is covered by two nuee ardente facies, a convent ional "Merapi-type", valley-fill block-and-ash Row facies and a pyroclastic surge facies, The proximal deposits reflect the accumulation of dozens of nudes ardentes, with many subsidiary flow units. The distal deposits are mo re simply organized, as only a few individual events reached to distances > 3.5 km, The stratigraphic relationships north of Turgo hill indicate that t he surge deposits are a facies of particularly mobile nuees ardentes that a lso deposited channeled block-and-ash flow facies. They further suggest tha t the surge facies beyond the channel margins correlate laterally with a fi ner-grained sublayer locally developed at the base of the block-and-ash Row facies. Eyewitness reports suggest that the emplacement of the block-and-a sh Row facies in the distal part of the Boyong river may have followed, by a short time interval, the destruction and deposition of the surge facies a t Turgo village, The stratigraphy is in accord with the eyewitness reports. The surge facies was emplaced by a dilute surge current, detached from the same dome-collapse nuee ardente that, as a separate flow unit, subsequentl y emplaced the distal block-and-ash deposit in the Boyong valley. The detac hment occurred at higher elevations, likely at or above the slope break at about 2000 m elevation. This flow separation enabled the surge current to s hortcut over the landscape and to emplace its deposit even as the block-and -ash Row continued its tortuous southward movement in the Boyong channel. D ome-collapse nude ardente activity formed the bulk of the eruption, which w as accompanied by virtually no significant vertical summit explosive activi ty. (C) 2000 Elsevier Science B.V. All rights reserved.