The Kurile Islands form a typical double island arc, which is chiefly composed of Quaternary volcanic rocks that overlie Tertiary basement rocks. The Quaternary volcanic rocks include andesite and basalt of the tholeiite and high-alumina basalt series, and calc-alkalic rocks derived from these two series. Data from 160 whole-rock chemical analyses show that the SiO₂ content of these rocks ranges from 45 to 70 wt percent. Basaltic rocks with 50 to 55 wt percent account for 24 percent of the analyzed rocks, and andesitic rocks with 55 to 60 wt percent SiO₂ make up 37 percent of the total.

There is a remarkable zonation of volcanic rock types in the Kurile arc. Rocks of the tholeiite series are mainly in the outer or Pacific zone, and rocks of the high-alumina basalt series are more abundant in the inner zone, adjacent to the Okhotsk Sea. This zonation is best defined in the northern Kurile Islands.