Volcán el Soche, a small stratovolcano near the Colombia border, is the northernmost of a chain of Ecuadorian volcanoes east of the principal volcanic axis.  The dominantly dacitic Soche volcano was constructed over Paleozoic rocks and has a summit caldera that opens towards the east.  A major explosive eruption took place during the early Holocene at about 8600 years BP, depositing tephra NW into Colombia.  The ejection of voluminous dacitic airfall pumice and pyroclastic flows was followed by the formation of two lava domes in the caldera.