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
Ice-marginal lava flow its subglacial beginnings. Currently the volcano is surrounded on all sides, except the south, by glaciers. What does Hoodoo mountain have to do with ice-marginal lava flows? Well, the entirety of the mountain is also surrounded by enormous lava cliffs, ranging from 50m-200m in height, as seen in Figure 3. The clearest example of these lava cliffs is seen on the southwestern side of the mountain whereas the northern formation of these cliffs has been overridden by recent lava flows and glacial erosion. Scientists are able to diagnose these lava cliff formations as a result of ice-marginal lava flows because