Magma erupted by Lascar appears to form from the mixing of mafic and more evolved magmas; the 1993 eruption deposits contain bands of different rocks. Specifically, basaltic andesite magma is periodically injected into a magma chamber, where crystal fractionation and mixing processes take place. The process happens frequently, thus the magmas are relatively unevolved; presumably, if the supply of mafic magma is steady, the products are andesitic, otherwise dacite forms. This origin of Lascar magmas is reflected in the textures of rocks. The overall magma supply rate of Lascar is .