The Cuicocha ( Kichwa Kuykucha, " Meerschweinchensee " or Kuychikucha, " Rainbow Lake ") is a caldera and a crater with a diameter of about three kilometers at the foot of Cotacachi in the Ecuadorian Andes ( Imbabura province ). The caldera was created by a massive phreatic eruption about 3100 years ago, a pyroclastic flow of about five cubic kilometers of material produced and the surrounding area up to 20 cm deep covered with volcanic ash. The volcano has been dormant since that time. He is, in connection with volcanic eruptions from the neighboring volcanoes such as Imbabura, the Mojanda, the Cotacachi and Cayambe, responsible for the fertile soil of Otavalo valley.
The endorheic crater lake inside the caldera contains four lava domes of dacite, which form two steep, forested islands. Access to these two islands called Yerovi and Teodoro Wolf is not permitted. The rim of the caldera is very steep and does not allow vegetation. An older lava dome from the Pleistocene forms part of the eastern margin. The lake, which is more than 200 m deep, is highly alkaline and contains little life.
On the islands of the lake there is life on the other hand; here be mentioned especially the Silver Grebe, who lives in the reeds and feeds on algae. Although this bird comes anywhere in the Andes before, but little is known about him. 1974 resulted in a count of a stock of 44 birds in Cuicocha.
Cuicocha forms the southern part of the reserve of Cotacachi - Cayapas. On the second day of Inti Raymi ( Sun Festival ) for the summer solstice indigenous Kichwa shamans take a ritual cleansing bath in Cuicocha.