The old views on the style of the Avachinsky eruptions during 1737- 1909 have partially been revised based on new data obtained by the authors. We specified their types and geological-geomorphological effect and made an assessment of the related volcanic hazards. All the eruptions were merely explosive except for the effusive-explosive eruption of 1894-1895. The eruptions of 1737, 1779 and 1827 are referred to large for this historical eruptive stage, the rest (of 1772, 1851-1855, 1878, 1881, 1894-1895 and 1909) are regarded as small and moderate.

We have summed up and supplemented new data on the eruptions of 1926-1927, 1938 and 1945 plus added the description of the last eruption of the volcano in January 1991. Considering the dynamics of the eruptive activity of the Avachinsky volcano in 1737-1991 we have presented a classification for these eruptions. Also we made a forecast of the type and parameters of possible future eruption as well as estimated the volcanic hazard associated with it. Because of high degree of volcanic hazard in the SW and S sectors of the base of the volcano it is proposed to prohibit constructions of any kind in these areas.

The article provides data on historical events of the Kurile island arc’s most active Peak Sarychev Volcano, Matua Island, the Central Kuriles. During the study period the volcano was producing short terminal eruptions of explosive and explosive-effusive types discharging volcanites chiefly with pyroclastic flows and related formations.

The dynamics of hostorical eruptions for Chikurachki Volcano has been analyzed. It is shown that these were either weak Strombolian-type eruptions (at intervals of a few years to a few tens of years) or powerful Plinian-type eruptions (at intervals of 100-200 years) discharging basaltic magma (50-54% SiO2). We have studied the tephra deposits and determined the parameters of the 1853 and 1986 Plinian-type eruption phases whose values have turned out to be similar: the minimum volume of erupted magma was 0.03 and 0.04 km3, respectively, the magma discharge was 5 x106 kg/s for both eruption types, the eruptive column height was about 13-14 km for wind velocities of 35-40 and 15 m/s, the Plinian-type phases lasting 5 and 7 hours. Information is provided on the morphology of the volcanic edifice and the structure of the soil-pyroclastic cover in the area. The condition of the crater in the summer of 2000 is described. It is concluded that high, pyroclastics-charged clouds of Plinian-type eruptions are the leading risk factor associated with Chikurachki Volcano.