Mars Orbiter Camera image (5.23 m/pixel) and topographic data from the Mars Orbiter Laser Altimeter data are used to analyze a channel on the upper northern flank of the Elysium Mons volcano, Mars. We show that this channel is best explained as the product of the thermal erosion of the preexisting surface by a high-speed, turbulent lava flow fed from a fissure eruption. We deduce the volume eruption rate (∼3400–13,000 m3/s dense rock equivalent), the total volume of erupted lava (∼29–39 km3 dense rock equivalent), and the duration of the activity (40–130 days). Perhaps significantly, the erupted lava volume is essentially identical, given the uncertainties in the analysis, to the volume of the observed caldera (∼31 km3), which has implications for volume-limited eruptions on Mars and potentially for the unusual steep upper slopes of the volcano. The eruption that produced the channel appears to have been typical for Elysium Mons and implies that the other lava channels on the upper flank of the volcano may also have taken ∼1–4 months to have formed.