Abstract

Bowie Seamount, situated off the west coast of Canada at 53° 18′ N, 135° 39′ W, is a long northeast-trending, volcanic mountain comprising a series of intersecting ridges. These ridges may have grown from extrusions along intersecting fractures in the oceanic crust. Two terraces form the flattened summit of the volcano at approximate depths of 80 and 235 m. These are thought to be remnants of platforms produced by combined shallow-water vulcanism and wave erosion during Pleistocene and Recent times when sea level was lower than it is today. The last episode of volcanic activity on the summit occurred after the formation of the upper terrace which is probably no more than 18 000 years old. Samples dredged from the upper half of the volcano include: pillow fragments, fragments of non-pillowed flows, pillow breccias, bombs, tuffs, ash, and unsorted tephra. The rocks are mainly alkali olivine basalts, accompanied by a few intermediate rocks which are believed to have been derived by differentiation of the basaltic magma.

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