Lava Beds National Monument

Lava Beds National Monument

Exploring the caves underneath the Earth's surface at Lava Beds National Monument

September 13, 2010, 9:40 am

Rounding the corner from Tule Lake, all you see is flatness and desolation -- a black volcanic jumble spewed from vents in a shield volcano 11,000 years ago. This still land has no wildflowers and no shrubbery. Devil's Homestead, they call it, and the name sticks in your head.

But underneath the Earth's surface at Lava Beds National Monument near Tulelake, Calif., is a web of 800 caves formed by streams of basaltic lava. Some two dozen of these caves are open to the public, which is why we're here on a hot summer day.

A playground of underground exploration and historical Modoc War sites, the remote and relatively undiscovered 47,000-acre national monument near the Oregon border makes for the perfect outdoor family adventure.

We are a raggedy group of four adults, five children and an 8-month-old ready to experience a lesson in volcanic geology that you can enter, crawl and climb through.

Most people think of volcanoes as mountains, but you'll see no real mountains in Lava Beds, which is on a shield volcano. Unlike the classic volcanic cone blowing off its top like Mount St. Helens, shield volcanoes are broad and shallow -- this one looks like a flat plain in a wide valley. This plain is built from many rivers of low-viscosity lava that flowed out of vents from a magma chamber deep under many layers of rock.

As lava flows on the surface, the outer edges cool in the air and harden into worm-shaped rock tubes, which remain after the lava has drained away. These tubes diverge and converge, forming a network of caves underlying the surface of the Earth. Unlike water-formed caves, these are dry and neat, with no stalactites or sinkholes. Even the floors are mostly flat because the last lava ebbing through them hardened in place, as would the frozen surface of a stream.

At the recommendation of the National Park Service, we're staying three days.

"The most common comment we get is, 'I needed to plan more time -- I could stay here for a week. We didn't realize how much there was to do,'" said Angela Sutton, a park ranger, when I called to plan the visit.