Lava Beds National Monument years BP to 1,110 years BP. Some of the major Lava Flows within Lava Beds National Monument include the: Callahan Flow; Schonchin Flow; Mammoth Crater Flow; Modoc Crater Flow; and Devils Homestead Flow. Gillem Bluff, a fault scarp, was created as the region stretched and a block of earth dropped down along this fault (see Basin and Range Province). The tuff layer on top of Gillem Bluff is 2,000,000 years old, indicating the rock layers beneath are even older. The oldest lava flow from the Medicine Lake Volcano within the monument is the Basalt of Hovey Point, near Captain Jack's
Boring Lava Field of Troutdale and more than 32 vents within a radius of Kelly Butte. Mostly small cinder cone vents, these volcanoes also include some larger lava domes from shield volcanoes at Mount Sylvania, Highland Butte, and Larch Mountain. The Boring Lava Field marks the densest volcanic vicinity in this group, with 20 volcanic vents encompassing an area of . It includes more than 80 known small vents and associated lava flows, with more volcanic deposits likely present under sedimentary rock deposits from the Missoula Floods (also known as the Bretz or Ice Age Floods), which took place between 21,000 and 15,000