Belknap Crater
Besides the volcanic vents related to Belknap Crater, there are two volcanoes south of Belknap which were also recently active: Four-in-One Cone and Collier Cone. Another, unnamed cone at the northern end of Inaccessible Cone's alignment, which rises to a height of , was breached on its western and southwestern sides by gray basalt lava, which is older than Sand Mountain Volcanic Field and Belknap. There may have been a large lava field in the glacier valley north of the Twin Craters cone, but any evidence is now buried under the Belknap shield. There is a glaciated steptoe (island) in the western part of the Belknap lava field. Deposits from Belknap buried older lava flows from the Sand Mountain Volcanic Field as well as a series of four cinder cones located about to the southwest of Mount Washington. There are also deposits from Belknap in the Lake Valley region between Belknap and both Sims Butte and Mount Mazama.