Tree imprints at Craters of the Moon

Our last point of outdoor exploration as we looped through the Pacific Northwest this summer was Craters of the Moon National Monument in south central Idaho. The monument, a large expanse of black rugged volcanics, interrupts the otherwise dry brown Snake River plain that stretches across the southern part of the state.

A relatively short road leads through the most easily-accessible part of the monument. It is perfect for a visit of only a few hours, which it turns out was all the time we had that day, and which it also turns out was plenty of summer sun exposure in a landscape mostly devoid of shade.

We first stopped at Inferno Cone, a smooth black cinder cone. My two boys dashed up the slope and I followed a few minutes later. The mountain is a smooth cone of volcanic ejecta, mostly black with an outcrop of some reddish rock near the top. Some of the lightweight black cinders were especially iridescent. The top of the cone provided panoramic views of the volcanic monument and mountains to the west. A strong wind blew gusts of warm dry air from the south. Inferno Cone wasn’t unlike the larger Cinder Cone at Lassen National Park that I described in an earlier post.

Three views of Craters of the Moon National Monument from Inferno Cone.

Pines and shrubs near the trail to the tree imprints.

The next stop was a short trail at the southern end of the road. The trail led south through dry shrubland with occasional occurrences of five-needled pines, most of which were probably not more than 10 meters tall. At some point along the trail we entered the Monument’s wilderness, which apparently is the first wilderness area that was ever designated in any National Park Service unit in the country.

The end of the maintained trail featured some usual imprints of ancient trees – technically fossils I would assume – that were immortalized in past flows of hot lava. The tree “molds” as they were called were of two types. The first type was trunks that were encased in lava and which later decomposed, leaving a cylindrical vertical hole in the newly hardened rock. The second type was horizontal impressions of fallen logs. In the more impressive examples of this type of mold, the texture of the tree’s bark was exceptionally preserved. The patterns in the rock looked much like the bark of pines and I wonder if the species immortalized in the lava could possibly be identified by carefully comparing the prints with modern species. 

Two types of tree "molds" preserved at the Monument.

This volcanic rock looked like a skull or a turtle shell to me.