Quimsachata was formed by a scoria cone and a lava field, next to the Vilcanota valley. It erupted about 11,500 years ago. Oroscocha () is a dome with two associated lava flows that reach thicknesses of . The volcano covers a surface area of . Oroscocha was erupted from a fissure about 4450 BCE, and the flow modified the course of the Vilcanota river.