Behm Canal-Rudyerd Bay

Geography & Climate

Behm Canal-Rudyerd Bay is located in United States, within the Northern Cordilleran Volcanic Province of the broader North America Volcanic Regions. Situated at 55.35° N, 131.00° W in the Northern Hemisphere, the volcano lies within a subarctic climate zone. At just 500 meters above sea level, Behm Canal-Rudyerd Bay is a relatively low-elevation volcanic feature. Despite its modest height, it remains an active geological formation with the same underlying magmatic processes as its taller counterparts. The volcanic landform is characterized as a cluster, which describes the physical shape and structure of the volcanic edifice as observed from the surface.

Geological Context

Behm Canal-Rudyerd Bay is an intraplate volcano, meaning it formed away from any plate boundary. These volcanoes are often powered by hotspots — plumes of abnormally hot mantle material rising from deep within the Earth. Hotspot volcanoes like Behm Canal-Rudyerd Bay tend to produce effusive eruptions with lava flows that can be relatively predictable, giving nearby communities in United States more time to prepare. However, they can also produce explosive phases, particularly when magma interacts with groundwater. The dominant rock type is basalt / picro-basalt, a dark, fine-grained volcanic rock that forms from rapidly cooling, low-viscosity lava. Basaltic eruptions tend to be less explosive and produce fluid lava flows that can travel long distances. While less immediately dangerous than explosive eruptions, basaltic lava flows can destroy structures and infrastructure in their path, and volcanic gases released during these eruptions can affect air quality over a wide area.

GVP Reference Summary

Numerous basaltic cinder cones and lava flows occur in the panhandle of SE Alaska on both sides of Behm Canal, which divides Revillagigedo Island from the mainland. The lava flows, which are locally columnar-jointed and overlie glacial-fluvial sediments and granitic gneisses of the Coast Mountains, are located on the E and SE sides of Revillagigedo Island and at Rudyerd Bay across Behm Canal to the east. Most exposures are on SE Revillagigedo Island, but outcrops also occur on the mainland east of Behm Canal at the southern end of Punchbowl Cove at Rudyerd Bay. Undisturbed cinder cones and lava-flow surfaces at Painted Peak on SE Revillagigedo Island and elsewhere indicate that most of the activity was post-glacial (Brew, in Wood and Kienle, 1990). Pumice, lapilli, and ash deposits locally cover parts of glaciated ridge tops. Lava flows at the outlet of Lake Grace near Behm Canal on the eastern side of Revillagigedo Island were considered to be of late-Pleistocene or Holocene age (Wanek and Callahan, 1971). Minor andesitic and trachyandesitic flows are also present.

— Smithsonian Institution, Global Volcanism Program