The volcanic record that gets away

Volcanologists are accustomed to looking at the record in the rocks to read volcanic history. They map the extent of airfalls, the thickness and distribution of ignimrites and mudflows, and the nature and extent of lava flows. From these data they infer the story of previous eruptive episodes that are a key to what we may expect in the future. BUt some important volcanic events are not recorded. Without observations at present-day active volcanoes we would know little about the volcanic gas emitted, the kidns of gases, or the volume and the extent o the gas cloud.