Magellan (and Pioneer Venus Orbiter (PVO)) found high mountain terrains on Venus (~2.5 km above 6051 km planetary radius) exhibit anomalously low radiothermal emissivity. This is thought to result from weathering of primary Venus rock, which at high altitudes produces a distinctive high-dielectric-constant mineral assemblage. Deviations from the nominal altitude-emissivity pattern have been used as a crude chronometric tool with which to date Venusian landforms. This technique indicates Maat Mons (an unusually large shield volcano, standing 9.17 km above 6051 km planetary radius, at 2.1 ¿N, 194.3 ¿E) has undergone a ''recent'' episode of large-scale volcanic activity; a deduction also implied morphologically. The present paper investigates whether a plinian eruption at Maat Mons could explain the enhanced concentrations of SO2 gas in the upper atmosphere of Venus that were detected by the Pioneer Venus UV spectrometer. The results show for a minimum vent radius of 156 m, a minimum eruption temperature of 1200 K, and a magmatic volatile content of ~5 wt %, a plinian eruption at the summit of Maat Mons can explain the anomalous concentration of SO2 gas. This would mean Maat Mons is an active volcano. ¿ American Geophysical Union 1995