Soil²²² Rn Pulse during the Initial Phase of the June–August 1995 Eruption of Cerro Negro, Nicaragua

The June–August 1995 eruption of Cerro Negro, a small-volume basaltic cinder cone in Nicaragua, provided a unique opportunity to quantify ²²² Rn degassing from soils in response to explosive volcanic activity. ²²² Rn was monitored at 29 stations using electrostatically charged teflon ²²² Rn detectors distributed north and southeast of the volcano. A pulse of elevated ²²² Rn degassing occurred early in the eruption along a > 1 km long zone, extending at least 750 m beyond the base of the cinder cone. Observation of this ²²² Rn pulse shows that large changes in soil ²²² Rn concentration can occur simultaneously at widely separated stations in response to even comparatively small-volume intrusions and volcanic eruptions. Frequent ²²² Rn sampling at multiple stations provides a sense of the magnitude, time scales and area affected by convective gas transport during volcanic eruptions.