Capital Mountain is a small shield volcano. It stands 4231 ft (1290 m) above the nearest plain. This volcano is 11 miles (18 km) across at the base. The caldera at the summit of Capital is circular with a diameter of 2.5 miles (4 km). It is filled with thick lava flows. Pillow lavas can also be found in the caldera. A 328 ft (100 m) high plug is located in the center of the caldera. The plug is made of andesite. Dikes lead to this plug from all directions. The shield lavas range from basalt to dacite. Most of the lavas and the dikes are andesite.
Sources of Information:
Wood, Charles A. and Klienle, Jurgen, "Volcanoes of North America United
States and Canada," Cambridge University Press, pp 89-90, 1990.
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