Volcanic activity at Anyuyskiy probably began with lava flows. These three lava flows have a total volume of and cover . In these thick lava flows lava lakes, lava tubes, and high swells have been found. This volcanic activity filled the valley of the Monni River and disrupted the course of its tributaries, resulting in the formation of a number of lakes. Characteristically, the lava flows slope from north to south, because the fissure vents are on the north side of the valley. Some of these fissure vents are exposed, forming ridges of lava. The lava flows probably interacted with permafrost soils.