Clarno Unit Clarno Palisades The palisade cliffs at the Clarno Unit are remnants of a series of volcanic mudflows called "lahars". Loose volcanic debris saturated with rainwater triggered the lahars which inundated sub-tropical forests growing beneath steep volcanoes 54-37 million years ago. Preserved in the lahars are world-class deposits of fossilized nuts, seeds, wood and leaves. The Palisades are best photographed in the morning or late afternoon hours. Trail of the Fossils This ¼-mile trail guides you to boulders from the palisades where erosion has exposed glimpses of a fossil forest. Arch Trail A steep, narrow, rocky ¼-mile trail takes you near petrified logs and limb casts. Hancock Field Station The Hancock Field Station, surrounded by the Clarno Unit, is operated by the Oregon Museum of Science and Industry and offers programs on the geology, paleontology, and ecology of central Oregon. For more information write: Hancock Field Station, Fossil, OR 97830.