On 15 June 1991 one of the largest volcanic eruptions of recent times occurred at Mount Pinatubo in the Philippines. The volcano had been dormant for over 600 years. The eruption produced high-speed avalanches of hot ash and gas, giant mudflows, and a cloud of volcanic ash hundreds of kilometres wide. Witness has been speaking to volcanologist, John Ewert, who was part of the team monitoring the volcano.(Photo: Clark Airbase Philippines. John Ewert 4th from right. Photo courtesy of John Ewert)