Quilotoa it is a water-filled boiler and the westernmost volcano in the Ecuadorian Andes. The 3 km wide boiler was formed by the collapse of this dacite volcano following a catastrophic eruption 800 years ago, which produced pyroclastic flows and lahars that reached the Pacific Ocean, and spread in the air a deposit of volcanic ash along the northern Andes. The boiler has accumulated a depth of 250 m crater lake, which has a greenish color as a result of dissolved minerals. Vents are on the bottom of the lake and hot springs occur on the eastern flank of the volcano.