The Raikoke Volcanic Massif (Kuril Island Arc)
The land-underwater volcanic massif Raikoke was studied. It is located in the northern part of the Central Kuriles, consisting of the island-volcano Raikoke and the quaternary submarine volcano 3.18. The volcano eruption in June 2019 suffered great losses to the Raikoke flora and fauna, once again changing its shape, and a lake appeared in the volcano crater. The Raikoke volcano island is composed of moderate potassium rocks of medium alkalinity of the tholeiite series from basalts to andesites, which are typical island arc lavas. For the first time data on the composition of 6 samples taken on it are published. Underwater volcano 3.18 at a depth of near 800 m merges with the base of island-volcano Raikoke. The ridge-top part, located at depths of 260–230 m, has several peaks; extrusions were revealed in the northeastern and southeastern foot parts. Volcano 3.18 is composed of andesite basalts and andesites. Andesite basalts belong to the moderate-potassium series of normal alkalinity lavas. The performed studies allowed us to assume that underwater volcano 3.18 was formed during the geomagnetic reversal. Supply channels and peripheral magma chambers were distinguished in its structure.