Thermal structure of the gas-and-ash plume during eruption of Koryak volcano

Abstract

High resolution thermal cameras were used in observations of gas-and-ash plumes during eruption of the Koryak volcano in March 2009. Our results provide the thermal structure of gas-and-ash flows. The structure of the eruption column consists of several individual plumes. The vertical velocity of plume rise was estimated at 5.5–7 m/s. The eruption column or plume can be conventionally divided into three parts: a highly convective region, a buoyant region, and a region of horizontal motion. The temperature of the plume is higher than that of the surrounding atmosphere by 3–5°C for the horizontal motion region and by about 20°C for the buoyant region. The velocity at the buoyant region is 5–7 m/s. For the boundary between highly convective and buoyant regions, where the plume diameter is known, the vapor mass flow and the heat capacity of the thermal jet flow can be determined from the heat balance equation. The mass flow of the overheated vapor, which has a temperature of 450°C and comprises a gas-and-ash eruption plume, was estimated to be Q = 35 kg/s. The total mass of water vapor over the period of eruption (100 days) is estimated at 3 · 105 t. The total thermal energy of the eruption amounted to 109 MJ.