An unusually energetic basaltic phreatomagmatic eruption: Using deposit characteristics to constrain dilute pyroclastic density current dynamics

Multiple, highly erosive base surges of the Table Rock Complex tuff ring (TRC2), Oregon, produced dune-bedded deposits with crest to crest bedform wavelengths up to 200m, which are amongst the largest ever recognized in the deposits of pyroclastic density currents. Here we use bedform wavelength, surmounted obstacles, and a large chute-and-pool feature to estimate near-source velocities (118-233ms ^-1), lower-bound velocities at radial distances of 1.6, 2 and 4.7km from source (34, 29 and 20ms ^-1, respectively), and corresponding column collapse heights (up to 2.8km). This paper represents one of the few studies that attempt to quantify flow characteristics, such as emplacement velocities at different distances from source, eruption column collapse height, and eruptive energy, based on deposit characteristics.