CGRG Bibliography of Canadian Geomorphology
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Author : Allen, C.C.
Date : 2000.
Title : Subglacial volcanoes (tuyas) of North-Central British Columbia, Canada.
Publication : Volcano/Ice Interaction on Earth and Mars, August 13-15, 2000, University of Iceland, Reykjavík, Iceland. Abstract Volume. Edited by: Gulick, V.C.; and Gudmundsson, M.T.
Issue :
Page(s) : 12.
Abstract
Hoodoo Mountain is a trachytic/phonolitic volcano located in northwestern British Columbia, ~ 100 km south of Mount Edziza, and ~300 km southeast of Mount Edgecumbe, Alaska. It is one of the largest peralkaline subglacial volcanoes in Canada, which is second only to Iceland and Antarctica in numbers of subglacial volcanic deposits. The evolution of Hoodoo Mountain is dominated by eruptions that were partly to entirely subglacial. The initial stages of eruption (at ~80 ka; [1]) generated thick, trachytic lava flows covered by deposits of monolithologic breccia, interpreted as hyaloclastite. The flows (units Qvap1,2) were eventually blocked by valley glaciers and form cliffs up to 210 m high around the volcano. These flows and breccias account for the lowermost 1/2 of the edifice. Between 80 and 54 ka [1], a thick sequence of pyroclastic debris erupted. The resultant poorly to strongly welded pyroclastic deposits are grouped stratigraphically into one unit (Qvpy). The explosive eruptions responsible for the formation of these deposits may have been in part subglacial or hydroclastic. Unit Qvpy is overlain by a series of apparently subaerial lava flows at ~54 ka (unit Qvap4 [1]). Subsequent eruptions formed a thick sequence of subglacial lava flows and hyaloclastite (unit Qvap5). This upper section of subglacial lava flows forms the bulk of the upper 1/4 of the volcano and comprises a variety of morphologic deposits, including large, lava lobes that are enclosed by hyaloclastite. Unit Qvap6 resulted from emplacement of dikes through Qvap5 into the overlying ice at 40-30 ka [1]. The most recent activity at Hoodoo Mountain (9-7 ka [1]) comprises highly porphyritic, phonolite/trachyte, subaerial lava flows (Qvpp). The present summit of the volcano (1800 m) is covered by a small icecap, which is ~ 3 km in diameter.
Bibliography of Canadian Geomorphology