期刊
JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH
卷 142, 期 3-4, 页码 193-205出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jvolgeores.2004.09.003
关键词
Mount Etna; lava morphology; lava flow emplacement; lava inflation; toothpaste lava; slab-crusted lava
Slab-crusted flows on Mount Etna, Sicily are defined here as those whose crust has ridden on the flow core without significant disruption or deformation and have a high length to width ratio. They typically erupt from ephemeral boccas as late-stage products on dominantly aa flow fields, such as that of the 1983 eruption on Mount Etna. Slab-crusted flows tend to inflate mainly as they approach and after they reach the maximum length of slab-crust formation, the flow interior acting as a preferential pathway for injecting lava under a stable crust. Coalescence of vesicles under successive crusts causes separation between core and crust giving a new cooling surface within the flow, on which ropy surfaces (and occasionally aa textures) of limited areal extent may develop. Slab-crusted flows tend to form at ephemeral boccas together with other surface textural types including toes, ropy pahochoe sheets and aa flows. This suggests that, on Etna, slab-crusted flows form from lava of the same theological properties as both aa and pahoehoe textured flows. They do not represent a transition between aa and pahoehoe as argued for toothpaste flows in Hawaii. We conclude that slab-crusted flows on Etna owe their morphology to a relatively high critical ratio of effusion rate to advance rate, related to vent cross-sectional area and the slope over which the flow forms. (c) 2004 Elsevier B.V. All rights reserved.
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