CGRG Bibliography of Canadian Geomorphology
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Author : Edwards, B.R. and Russell, J. K.
Date : 1997
Title : Terrestrial subglacial volcanism: glacial influences on volcanic morphology and eruption products at the hoodoo mountain volcanic complex, northwestern British Columbia [abstr.]
Publication : Geological Society of America, 1997 Annual meeting, Abstracts with Programs - Geological Society of America. Oct. 20-23, 1997, Salt Lake City
Issue : 29(6):
Page(s) : 137
Abstract
Volcanic eruptions in glacial environments produce unique volcanic products (e.g., hyaloclastite, pillowed lavas, pillowed lava breccias) and unique volcano morphologies (e.g., tuyas / table mountains, tindars). The Late Quaternary Hoodoo Mountain volcanic complex provides a dramatic case study of the physical evolution of two compositionally distinct volcanic edifices (basaltic and phonolitic) in a supra- and subglacial environment. Little Bear Mountain volcano (approximately 0.25 cubic kilometers in volume) erupted beneath glacial ice and comprises pillowed alkaline basalt lavas, pillowed lava breccias, and hyaloclastite deposits. The volcano is bounded on the north and east by a large valley glacier, and the drumlinoid shape of the volcano attests to strong, post-eruption morphological shaping by surrounding glaciers. The adjacent and much larger Hoodoo Mountain volcano (approximately 17.5 cubic kilometers in volume) is phonolitic/trachytic in composition. Its stratigraphy is dominated by glacially-influenced volcanic deposits. The stratigraphically lowermost lava flows were confined by glacial ice and form cliffs up to 210 m in height on the north and west. The lavas are always highly jointed and the joint sets are commonly irregular in orientation and size. The uppermost stratigraphy is dominated by monolithologic breccias with variable clast to matrix ratios that are intercalated with highly jointed, irregular lobes, spires, and domes of dense, aphanitic lava. The breccias are cross-cut by dykes, some of which also erupted subglacially and produced what are now ridges of highly vesicular aphanitic lavas with carapaces of pumiceous tephra (interpreted as hyaloclastite). The deposits have morphologies similar to basaltic tindars described from Iceland. The slightly rounded summit, the symmetrical shape, and the bounding cliffs at Hoodoo Mountain make it a volcano whose morphology is unique among terrestrial volcanoes except for its subglacial, Icelandic, morphological twin, Herdubreid.
Bibliography of Canadian Geomorphology