Evidence from stratigraphic relationships and petrographic analyses indicates that most upright tree stumps at Specimen Ridge in Yellowstone National Park were buried in place. These stumps are commonly rooted in a fine-grained tuffaceous sandstone that shows no petrographic evidence of being deposited by current action; in fact, most sandstones have textures resembling immature soils. Conglomerates that overlie these root-zone sandstones flow around and bury the vertical trunks. Trees were apparently killed in place by either mudflows or rising lake waters, giving rise to discontinuous, localized clusters of preserved trees in a given stratigraphic interval. However, the episodic nature of mudflow sedimentation indicates that these stacked clusters are likely remnants of successive forests with enough time between them to allow for incipient soil development.