Lava River Cave: A Mile Underground

Twelve miles south of Bend on United States Highway Ninety Seven, there is a trapdoor in the earth. A short walk from the parking lot leads to a staircase descending into darkness, and at the bottom of that staircase is the longest continuous lava tube in Oregon. The Lava River Cave extends about a mile into the earth before the passage becomes too small to navigate.

The round trip walk through it is about two miles. The cave formed roughly eighty thousand years ago when a lava flow moved across the high desert plateau and the outer crust solidified while molten rock continued to flow through the interior. When the flow finally drained, the hardened shell remained as a hollow tube.

Inside, the cave maintains a temperature of about forty two degrees Fahrenheit year round, which means it is cold even in August and shocking in summer when visitors descend in short sleeves. The ceiling height varies, reaching nearly sixty feet in some sections and dropping to just a few feet in others. Lava formations on the walls and floor record the behavior of the flow that created the tube.

The cave is managed by the Deschutes National Forest. It is a piece of the volcanic geography of central Oregon that requires going underground to understand. The entire High Desert plateau around Bend rests on a foundation of lava and ash.

Most of the time that fact is abstract. In the Lava River Cave it becomes physical and immediate: you walk through the hollow channel of a flow that moved across this ground eighty thousand years ago.