Plio-Pleistocene Volcanic Field

Metropolitan Portland, like Auckland, New Zealand, includes most of a Plio-Pleistocene volcanic field. The Boring Lava includes at least 32 and possibly 50 cinder cones and small shield volcanoes lying within a radius of 13 miles of Kelly Butte, which is 62 miles west of Mt. Hood and the High Cascade axis -- (Web note: Kelly Butte is approximately 4 miles east of downtown Portland)-- . Only the Clear Lake volcanics in California lie as far west in the coterminous United States. Unlike Clear Lake, Boring Lava vents have been inactive for at least 300,000 years. Allen, 1990, IN: Wood and Kienle, 1990, Volcanoes of North America: United States and Canada: Cambridge University Press, 354p