A mathematical model and a method of computation are developed for the flow of magma with temperature-dependent viscosity in the conduit of a volcano. An example involves the following parameters: conduit radius is 10 m, depth to the magma chamber is 30 km, the overpressure, magma temperature and viscosity in the chamber are 20 bars, 1300° C, and 104, Ю5, 106Pa s, respectively. The initial phase of conduit operation lasting less than 10 years is considered. Conditions are determined under which the conduit freezes (stopping the extrusion), a quasistationary behavior sets in (steady flow), and the flow heats the conduit wall intensively.

Records of microbarographic instruments in the near zone (45 and 113 km) were used for a detailed analysis of wave disturbances in the atmosphere accompanying the November 12, 1964 Shiveluch eruption. It is shown that the wave disturbances due to this major explosive eruption were largely caused by the formation of a convective column; they provide information on the time history of the eruption and the amount of erupted ash. The relation between seismic and acoustic intensities shows that the eruption started with a giant landslide (1.5 km3) giving rise to an ash cloud that produced the first acoustic signal. Volcanic tremor began 12 min after the slide and a second acoustic source began operating. This was related to starting Plinian activity and eruption of pyroclastic flows. The transition from one phase of the eruption to the next was accompanied by increased volcanic tremor and acoustic signal component of frequency > 0.05 Hz, as well as by generation of a long period (greater than 10 min) disturbance having an excess pressure of 50 Pa at 113 km distance. The amount of ash ejected into the atmosphere as inferred from long period disturbance energy is estimated to be 0.35-0.45 km3, which is in satisfactory agreement with geological evidence (0.3 km3).