Where did the lava come from and how did the caves form?
Lava Beds is located on the slopes of the massive Medicine Lake shield volcano, part of the Cascades volcanic belt that includes Mt. St. Helens, Mt. Rainier, and dozens of other volcanoes of the Pacific Northwest. Eruptions as recent as 1000 years ago spilled massive lava flows over this area. During the course of these eruptions, some of the lava flows cooled on the outside, but stayed molten in their middle. This molten lava then flowed away, leaving only the cooled outer edges, which remained as lava tube caves. More information can be found in our Nature & Science section.
