Ember Ridge comprises eight discrete andesite lava masses arranged in a crescent between Mount Fee and Tricouni Peak in the south central Mount Cayley volcanic field (MCVF). These volcanoes consist of jagged to bulbous, steep-sided lava piles whose cooling joint orientations and minimal erosion indicate that their modern shapes approximate their original morphologies. They range in horizontal dimensions from 180 m to 1100 m and in thickness from 30 m to 140 m, and are almost ubiquitously flanked by volcanic scree (rubble). Five of these volcanoes were originally mapped as “Ember Ridge” by Souther (1980). A sixth (Ember Ridge Northeast) was identified during field work conducted in 2001 (Kelman et al., 2002; Kelman, 2005). The two lava masses at Mount Brew have not been studied in detail, but are morphologically and compositionally similar to the other Ember Ridge masses, and are probably similar in age and eruptive style. All eight masses represent eruptions from isolated point sources beneath ice, and likely involved eruptions into well-drained glacial ice cavities without significant penetration of the ice surface. Discounting the effects of erosion (which has been minimal) the volcano shapes and cooling joint characteristics at the Ember Ridge masses are due to some combination of lava flows exploiting the shapes of pre-existing cavities or fractures, eruption on steep or irregular surfaces, collapse of portions of domes during eruption to form breccias, and disruption of earlier-formed cooling units by later pulses of lava. The ages of the Ember Ridge volcanoes are not known precisely, but they were almost certainly erupted during the Fraser Glaciation (25,000-10,000 years ago), probably during its latter stages.

Ember Ridge West consists of a single lava flow up to 60 m thick, sitting atop a basement ridge. The north side of the mass is steep, while the south side has a gentler profile. A small amount of volcanic breccia is present.

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