The Fourmile Hill Tree Molds south of Lava Beds National Monument, California contains tree mold casts from ancient trees that are now long gone.  When a volcanic eruption 12,000 years ago went off here at the Medicine Lake Volcano, it sent lava down this hillside & covered the forest, encasing these former trees & causing them to charcoal & burn up.  As the charcoal disappeared it left these casts, up to 15-20 feet deep w/ branches & other unique features of the tree intact in the lava.  This is the interior of one of the casts of a former large tree looking up to the sky from 15 feet down, the bottom is actually connected w/ a crawl to two other nearby tree casts.