Thermal erosion; observations on terrestrial lava flows and implications for planetary volcanism [abs.]

TitleThermal erosion; observations on terrestrial lava flows and implications for planetary volcanism [abs.]
Publication TypeConference Paper
Year of Publication1990
AuthorsPinkerton, H, Wilson L, Norton G

During recent fieldwork on Ol Doinyo Lengai in N. Tanzania two of the authors observed that small carbonatite lava flows were eroding their substrate at rates of a few millimetres/minute [l]. The resulting sinuous channels are similar, morphologically, to some lunar sinuous rilles. Here we assess how these channels formed, and compare measured and theoretical erosion rates at the base of active carbonatite and basaltic lava flows. Sinuous channels in volcanic areas can be formed by a variety of processes. Some are clearly collapsed lava tubes [2]; others are constructional features [3]; and it has been proposed [4,5] that others form as a consequence of thermal erosion at the base of long duration, turbulent lava flows. Measurements of the erosion rate at the base of a small channel, at a distance of less than l metre from its source, indicated that the erosion rate remained constant, over the period of observation, at 2 mm/min. Finally, using the thermal properties for basalts given above, together with the channel dimensions, discharge and viscosity data for the 1984 Mauna Loa eruption [12,13], calculated thermal erosion rates under laminar flow conditions vary from 0.22 m/day, l km from the vent, to 0.06 m/day, 4.5 km from the vent. This eruption is not unique; many other terrestrial lava flows will have had higher discharge rates in channels of similar dimensions. It is therefore clear that thermal erosion under laminar flow conditions must take place in the proximal channels of many basaltic lava flows. Difficulties in measuring lava depths in active channels explain why this process has been recognised on only a few occasions. To date, most analyses of sinuous rilles and similar lava channels on the moon [14] and Mars [15] have assumed turbulent flow conditions; these measurements need to be re-assessed in the light of the present findings. We predict that, in most cases, somewhat lower effusion rates will be inferred for the formation of channels than has been assumed in the past.

Original PublicationLunar and Planetary Science Conference, 21st, Abstracts
Source OrganizationNational Park Service
Source ProjectIRMA portal