for picnicking. In addition to the nature park on Hogan Butte, a number of smaller cinder cones are also publicly accessible. The Gresham Saddle Trail traverses Gresham Butte and Gabbert Butte, running for . The trail is considered to be of moderate difficulty, and it offers no amenities. It includes the Gabbert Loop Trail, which extends for through forests of maples, alders, ferns, and firs. Notes [a] Evarts et al. (2009) list only 80 centers but acknowledge there are likely more buried vents; Le Corvec et al. (2013) list 88 volcanic centers at Boring Lava Field. [b] Low-K is a geological term used to describe lava with low amounts of potassium, while high-K describes lava enriched in potassium. [c] Refractory refers to any material that does not easily convert from liquid to gas via the process of vaporization, which includes elements and compounds made from metals. References Sources . . . . . . . . . External links USGS Map of Boring Lava Field Volcanic fields of Oregon Volcanic fields of Washington (state) Subduction volcanoes Cascade Volcanoes Extinct volcanoes Pliocene volcanism Pleistocene volcanism Lava fields Geography of Portland, Oregon