Morphological data are at present our major source of information for extraterrestrial lavas. Effusion conditions must therefore be inferred from the final shapes of flow fields, generally using terrestrial lavas as analogues and so presupposing similar emplacement regimes on Earth and other planets. Studies of terrestrial lavas suggest that the overall development of flow fields is systematic and that a general, normalized relation can be established linking the final dimensions of a flow field (specifically, average thickness and the ratio of maximum width to maximum length) to underlying slope and eruption duration, independent of explicit knowledge of discharge rate, gravitational acceleration, lava density, and rheology. This relation is applied to lavas on the Martian volcano Alba Patera, on which two distinct planimetric types of lava flow fields are identified, and eruption durations, average discharge rates, and average velocities are obtained. Imposing the constraint of a terrestrial emplacement regime, the model yields internally consistent results for subliquidus lavas and suggests that, at least for basaltic-basaltic andesitic compositions, the essential conditions of eruption may have been similar to those currently observed on Earth.