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The Cuicocha volcanic caldera lake is located on the Western Cordillera, some 110 km to the north of Ecuador’s capital Quito and some 25 km northwest of Otavalo in the province of Imbabura and represents besides Quilotoa (fig 23), one of the two active volcanic lakes in Ecuador. Cuicocha, is truncated by an elliptic caldera of maximum 3.2 km in diameter. Both, Cotacachi and Cuicocha are situated along a fracture zone called the Otavalo-Umpalá fracture zone. |
| while Cuicocha volcano is having four domes distributed in the two islands in the center of the lake (Island Yerovi 0.26 km2 and Island Wolf 0.41 km2, respectively) and one in the ENE-rim of the caldera wall, all of them being andesitic in composition. Caldera walls are steep with angles between 45° and 75°. |
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The Cuicocha volcano initiated its activity with intense eruptions and lahars (volcanic mud flows, mainly composed of ash and debris) some 4500 years ago and continued until some 1300 years B.P. with the caldera formation and dome collapses and subsequent pyroclastic flows (flows composed of hot gas, ash and rocks) some 3000 years ago as yielded by radiometric dating. As result of this activity massive pyroclastic deposits of the mentioned flows are distributed in the surroundings of the caldera, but mainly to the east sector of Cotacachi (fig 29a-c, 30). |
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The caldera of the Cuicocha volcano is filled up with water formed by the deglaciation of the neighbouring Cotacachi volcano, rainwater and hydrothermal water giving rise to a maximal lake depth of 148 meters and a total lake volume of some 0.28 km3 and a surface altitude of 3072 m.a.s.l.. There is no actual visible inflow and no direct outflow. The yearly water level decrease of some 12 mm is the result of a nearby spring served by the lake.
The caldera lake, which is divided into two different basins with different depths of 148 m to the eastern part of the caldera and 72 m to the western side of the islands respectively, is partially filled up with slope debris and some sediments from the catchment area before the water accumulation began. Post-volcanic activities are expressed by the emission of volcanic gases in different parts of the lake in form of gas bubbles and some dead vegetation as result of these gases in the northernmost side of the eastern volcanic island.
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