A subaqueous eruption in Karymsky lake in the Academii Nauk caldera dramatically changed its water column structure, water chemistry and biological system in less than 24 h, sending major floodwaves down the discharging river and eruption plumes with ash and gases high into the atmosphere. Prior to the eruption, the lake had a pH of about 7, was dominated by bicarbonate, and well stocked with fish, but turned in early 1996 into a stratified, initially steaming waterbody, dominated by sulfate with high Na and K levels, and devoid of fish. Blockage of the outlet led to rising waterlevels, followed by dam breakage and catastrophic water discharge. The total energy input during the eruption is estimated at about 1016 J. The stable isotope composition of the lake water remained dominated by the meteoric meltwaters after the eruption.

The paper discusses the results of geodetic investigations performed in the region of the large 1975-1976 Tolbachik fissure eruption in Kamchatka. Using data from repeated triangu-lation and trigonometric levelings, horizontal and vertical displacements have been detected in an area of 3,500 km2. Two zones have been recognized: the tension and uplift zone that is probably due to magma intrusion from depths to the surface along the line of new cones and the extensive compensative subsidence zone located at a distance of 20-50 km from the nearest newly-formed cones.??Measurements made with small distance measuring device showed the dynamics of feeding basalt dykes intrusion and made it possible to determine their width (a little greater than 1 m) and magma and gas overpressure (50-250 bar). Data have been obtained on dimensions and growth of cones and on vertical ground deformation in the area of new cones during and after the eruption.??

Fumarolic steam plumes and eruption clouds rise like convetive turbulent columns into the atmosphere. Formulae are presented here for estimating the heat power of plumes, the production rate of juvenile pyroclasts ejected during eruptions and the heat output of fumaroles. Their accuracy is tested using the well-studied examples of eruptions of Kamchatkan volcanoes.
The Briggs (1969) formula may be used in observing the ascending part of a plume in crosswinds. The best results have been obtained using the CONCAWE formula which permits estimation of the heat power in crosswinds based on the axis height of a horizontal part of a maintained plume. Three connected equations have been suggested for a stable atmosphere and calm weather conditions. The first one, which is applicable for heights ranging from 100 m to 1 km, is the formula proposed by Morton et al. (1956). This equation changes for higher layers of the troposphere (1–10 km) and stratosphere (10–55 km).
A classification scale was constructed allowing us to compare volcanic eruptions and fumarolic activity in terms of the intensity of their plumes.
The described method is useful for volcano surveillance; it helps in the study of the energetics and mechanics of volcanic and magmatic processes.