Deschutes & Ochoco National Forests
Crooked River National Grassland

Geologic Sites

Lava River Cave

Lava River Cave is an excellent example of a lava tube and is the longest continuous tube in Oregon.

During long-lived eruptions flowing lava becomes channelized into a few main streams. Overflows of lava from these streams solidify quickly and plaster on to the channel walls, building natural walls that allow the level of the lava to be raised. Lava streams that flow steadily in a confined channel for many hours to days may develop a solid crust or roof and thus change gradually into streams within lava tubes. If molten rock (magma) stops rising to the surface at the source, the still-molten lava moving beneath the crusted-over top of a lava flow can continue to drain downhill and may ultimately leave an open lava tube cave. Because the walls and roofs of such tubes are good thermal insulators, lava flowing through them can remain hot and fluid much longer than surface flows. Tube-fed lava can be transported for great distances from the eruption sites.

The eruption which formed this cave occurred about 80,000 years ago. The source is believed to be near Mokst Butte but it has been buried by younger flows. This flow underlies much of Bend and nearly reaches Redmond.