This paper presents the results from a study of ash compositions that were erupted in 2013–2016. The juvenile component has been identified in the ejecta using data on the morphology and textural features of ash particles and the composition of volcanic glasses. The data set suggests that the activity of the volcano was phreatomagmatic.

The study of moraines at the Avacha volcano group revealed that glaciers changes at all volcanoes within the group happened almost synchronously. Glacial deposits could be grouped into three generations, corresponding to three periods of glacier fluctuations in Neoholocene. The largest glaciation within the group occurred ~2000 years ago. Fragments of moraine, corresponding to that period were found only in the moraine complex of the Ditmar Glacier which was 15% larger then today at that time. The most of moraines at the Avacha volcano group were formed during the Little Ice Age, which in the studied region continued up to the first decades of XX centuries. The maximal advance of glaciers probably happened in XVII century. The moraine corresponding to that period was found at the Kozelsky Glacier valley. At present time the total area of glaciers which moraines were described and dated approaches 21.46 km2. The area of reconstructed moraines corresponding to the Little Ice Age is estimated to be 2.79 km2, therefore at that period the total glaciation area reaches 24,25 км2 exceeding the present area by 13%. It could be claimed that in general during the time past the Little Ice Age the glaciation nature and glacier types did not change sufficiently. The rate of glacier degradation at various parts of the group is different and depends mainly on exposition. At the valleys of four glaciers we found moraines formed in the middle of XX century. They may appear in 1941–1952 when the unfavorable weather conditions leaded to stable negative anomalies in accumulation have happened.

The paper presents main glaciological characteristics of present-day glaciers located on the Koryaksky volcano. The results of fieldwork (2008–2009) and high-resolution satellite image analysis let us to specify and complete information on modern glacial complex of Koryaksky volcano. Now there are seven glaciers with total area 8.36 km2. Three of them advance, two are in stationary state and one degrades. Moreover, the paper describes the new crater glacier.

The paper presents main glaciological characteristics of present-day glaciers located on the Koryaksky volcano. The results of fieldwork (2008–2009) and high-resolution satellite image analysis let us to specify and complete information on modern glacial complex of Koryaksky volcano. Now there are seven glaciers with total area 8.36 km 2 . Three of them advance, two are in stationary state and one degrades. Moreover, the paper describes the new crater glacier.

The present-day glaciation of the Avachinskaya volcano group was analyzed using data obtained during field works of 2007–2010. Twenty seven glaciers were found on the volcanic slopes with their total area of 24.04±3.6 km2. These glaciers belong to eight morphological types, the largest part of them are glaciers of slopes, cirques, and barrancoes. Great extent, diversity of climatic conditions and volcanic edifices made possible to group the glaciers into three glacial knots (complexes): the Avachinsky complex, the Koryaksky volcano, and the Pinachevsky Range, each one with own specific features. Comparison of recent data with aerial photographs of 1974 has allowed estimating changes of the glacier front positions and to reconstruct the glacier dynamics for the last 40 years. At the present time, seven glaciers advance, two ones degrade, and eighteen glaciers are in the stationary state.

The present-day glaciation of the Avachinskaya volcano group was analyzed using data obtained during field works of 2007–2010. Twenty seven glaciers were found on the volcanic slopes with their total area of 24.04±3.6 km2. These glaciers belong to eight morphological types, the largest part of them are glaciers of slopes, cirques, and barrancoes. Great extent, diversity of climatic conditions and volcanic edifices made possible to group the glaciers into three glacial knots (complexes): the Avachinsky complex, the Koryaksky volcano, and the Pinachevsky Range, each one with own specific features. Comparison of recent data with aerial photographs of 1974 has allowed estimating changes of the glacier front positions and to reconstruct the glacier dynamics for the last 40 years. At the present time, seven glaciers advance, two ones degrade, and eighteen glaciers are in the stationary state.

Рис. 4. Положение облака, содержащего диоксид серы, связанного с извержением Толбачика (по спутниковым дан ным AIRS за 29.11.2013г., 02:53 UTC).Концентрация приведена в единицах Добсона (DU) (единица Добсона равна 0.01 мм толщины сжатого слоя озона при 0°C или 2.69 ⋅ 10 20 молекул озона на 1 м 2 ).Штриховая линия -границы спут никового снимка.

The dynamics of magmatic melts in the near-surface part of several kilometers depth is determined by gas release processes. Formation of free gas share is an energy source, while decreasing of the density of the melt creates conditions for magma motion to the Earth's surface. As the water content in the total volume of gas is about 80% for magmatic basaltic melts, gas release of water in the near-surface part of the magmatic column realizes the main share of energy, which leads to volcanic bursts and continuous gas-ash flows throughout the eruption process. Gas release processes create pressure variations in magmatic melts, and these variations are transferred into the solid medium as elastic oscillations forming seismic waves. The principal frequency of seismic signals for active volcanoes is several hertz, and the presence of spectral peaks has been explained by the presence of resonant sources.