The present volume seems to me to be a particularly im­ portant one for several reasons. Not least among these is the fact that it summarizes the work of two decades by G. S. Gorshkov, one of the world's leading volcanologists. In addition, it is the first general work of this length on the volcanism of what might be called a "narrow" island arc, a relatively simple megastructure as com­ pared with the "wide" arcs such as Japan and Indonesia. Finally, in this volume Gorshkov has summarized and cited extensive evi­ dence for his general ideas on the relation between volcanism and the earth's crust and mantle. A few potentially troublesome items should be noted here. In the translation the Russian terms "suite" and "series" have been retained, though for American readers these might better have been translated as "formation" and "group. " In almost all cases Russian place names have simply been transliterated rather than translated (e. g. , "Yuzhnyi Isthmus" rather than "South Isthmus"); in a few cases the English equivalent has been given in brackets where this is essential to the understanding of the author's com­ ments. The adjectives have retained their Russian case endings in the process (masculine -yi or -ii, feminine -aya or -'ya, neuter -oe) and this may occasionally lead to some slight confusion, for example, when the author calls a given feature Severnyi Volcano at one point and Severnaya Mountain at another.

Since Bezymianny Volcano resumed its activity in 1956, eruptions have been frequent; recently with up to 1–2 explosive events per year. To investigate deformation related to this activity we installed a GPS network of 8 continuous and 6 campaign stations around Bezymianny. The two striking observations for 2005–2010 are (1) rapid and continuous network-wide subsidence between 8 and 12 mm/yr, which appears to affect KAMNET stations more than 40 km away where we observe 4–5 mm/yr of subsidence, and (2) only the summit station BZ09 shows slight deviations from the average motion in the north component at times of eruptions.
The network-wide subsidence cannot be explained by tectonic deformation related to the build-up of interseismic strain due to subduction of the Pacific plate. A first order model of surface loading by eruptive products of the Kluchevskoy Group of Volcanoes also explains only a fraction of the subsidence. However, a deep sill at about 30 km under Kluchevskoy that constantly discharges material fits our observations well. The sill is constrained by deep seismicity which suggests 9.5 km width, 12.7 km length, and a 13° dip-angle to the south-east. We infer a closing rate of 0.22 m/yr, which implies a volume loss of 0.027 km3/yr (0.16 m/yr and 0.019 km3/yr considering surface loading). Additional stations in the near and far field are required to uniquely resolve the spatial extent and likely partitioning of this source.
We explain the eruption related deformation at BZ09 with a very shallow reservoir, likely within Bezymianny's edifice at a depth between 0.25 km and 1.5 km with a volume change of 1–4 × 10− 4 km3. Much of the material erupted at Bezymianny may be sourced from deeper mid-crustal reservoirs with co-eruptive volume changes at or below the detection limit of the GPS network. Installation of more sensitive instruments such as tiltmeters would allow resolving of subtle co-eruptive motion.