Geological Society of America

236 Volcanology (Posters)

Wednesday, 7 November 2012
9:00 AM - 6:00 PM
Hall B

REACTIVATION OF THE DORMANT CUICOCHA CALDERA LAKE, NORTHERN ECUADORIAN ANDES

Paper number: 236-9
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Theofilos Toulkeridis Presenting Author
Escuela Politécnica del Ejército, Quito, N/A
Melián Rodríguez
Instituto Tecnológico y de Energías Renovables (ITER), Tenerife, N/A
Hernández Martín
Instituto Tecnológico y de Energías Renovables (ITER), Tenerife, N/A
N. Perez
Instituto Tecnológico y de Energías Renovables (ITER), Tenerife, N/A
R. Buchwaldt
Massachusetts Institute of Technology, Cambridge, MA

Abstract

The volcano Cuicocha is a relatively young lake-filled caldera system, which is situated in the western volcanic cordillera of the Ecuadorian Andes. A series of eruptions and collapses (VEI=6) led to its present morphology leaving five andesitic-dacitic lava domes. Four of the domes making up two islands in the center of the 3.2 km wide elliptic shaped caldera. After main magmatic activity culminated some 1300 years ago, a lake developed. The lake was filled with some melting water from the now disappeared glacier located on the juxtaposed Pleistocene Cotacachi volcano, and some hydrothermal and rain water. Cuicocha has been the focus of various limnological, geological and volcanological studies. A constant of all studies is the steady and permanent presence of CO₂emissions, detected either by sonar in deeper lake levels, or seen as smaller bubbles in various parts of the lake surface. To assess the potential reactivation permanent monitoring of the geophysical, and geochemical changes of this volcano was carried out.

Since the end of 2011 till the beginning of 2012 a few minor seismic events have been felt by the public living close to the caldera. The official position indicated that all seismic movements where the result of active geological fault with seismic intensities of 1.5-2 Mw around 5 km below the caldera, and was not related to any magmatic activity of the volcano. Even more, it was officially stated that gas and water samples had been taken of the caldera lake before and after the seismic events indicating no changes of the volcanic activity, tranquilizing the public and press. In contrast our recent geochemical survey of the Cuicocha volcanic lake demonstrates an alternative view. We performed in July 2006 and in July 2012 an extensive soil and lake CO₂ efflux survey noticing tremendous changes between the two expeditions. While caldera rim and lava dome data remain practically unchanged (average g m^-2d^-1 = 4 and 8 for rim and domes respectively), lake data differ by an average of up to 20 times higher values. This evidences a certain elevated state of activity of the Cuicocha volcanic caldera lake based either on a single shake of the caldera lake bound gas due to the seismic activity or by a reactivation of the volcano by a magmatic pulse.