Maitland Volcano was a Pliocene age shield volcano in the western Cassiar Mountains of northwestern British Columbia, Canada. In the course of one million years, Maitland Volcano was formed on a mature, eroded Tertiary surface by rifting of the North American continent as thin alkali olivine basalt and hawaiite lava flows covered the surrounding area. In the four million years since the volcano was active, erosion has been extensive, exposing a cluster of 14 steep-sided volcanic plugs and scattered, cliff-bounded basalt lava flows that were originally part of the >900 km shield volcano. All volcanic plugs are about 30 m (98 ft) wide and are the only known vents for the basaltic and hawaiite lavas. The cliff-bounded basalt lavas cover the higher mountains of the Cassiar Mountains and individual lavas covering the mountains are up to 230 m (755 ft) thick and contain from 1 m (3 ft) to 20 m (66 ft) lava flows of columnar basalt separated by beds of scoriaceous flow-topped breccia and tephra. Intervening valleys, deeply incised into the underlying Jurassic shale and sandstone, are as much as 600 m (1,969 ft) below the base of the former Maitland shield volcano. These volcanics form part of the rift-related Northern Cordilleran Volcanic Province.

• http://en.wikipedia.org/wiki/Maitland Volcano