Channeled flow: Analytic solutions, laboratory experiments, and applications to lava flows

Although channeled lava flows are common in basaltic volcanism, relationshi ps between channel morphology, eruption and emplacement parameters, and lav a properties are not well understood. Several models have commonly been use d to constrain these relations, but they have not been well tested on natur al or simulated lava flows over a wide range of parameter space. Here, we t est the accuracy and assumptions of a moderately simple analytic rectangula r channel solution by comparing the behavior of well-controlled laboratory polyethylene glycol (PEG) channeled flows to the analytic solution for isot hermal, steady Newtonian flow in a rectangular channel with constant dimens ions. This analytic solution agrees well with laboratory measurements. Volu metric effusion rates (Q; m(3) s(-1)) calculated from the analytical model using measured PEG flows as input yield ratios of Q(calculated)/Q(pumped) o f similar to0.2 to 3.6, and flow rates calculated from a best fit surface v elocity profile to measured velocities give more accurate ratios of similar to0.8 to 1.2. We find a very weak dependence of solution accuracy on slope , attributable to flow front effects within the laboratory flows. We subseq uently apply the solution to several subaerial and submarine terrestrial fl ows as well as extraterrestrial channeled flows over a wide range of flow p arameters. Viscosity ranges and flow rates obtained using measured channel dimensions and assumed lava properties are plausible. Interestingly, the re sulting extraterrestrial estimates of viscosities and flow rates tend to fa ll closer to known terrestrial measurements and estimates of channel flow t han to previous planetary estimates. We therefore suggest that the analytic Newtonian rectangular channel flow model is a more appropriate physical mo del for many channeled terrestrial and planetary flows than the Newtonian i nfinite sheet flow and approximation to Bingham channel flow widely used pr eviously.