GNGTS 2017 - 36° Convegno Nazionale

202 GNGTS 2017 S essione 1.3 2010 - 2016 Geodetic Monitoring of Nevado del Ruiz, Colombia M. Ordóñez 1 , R. Adamo 2 , C.M. López 1 , M. Battaglia 2 1 Colombian Geological Survey, Volcanological and Seismological Observatory of Manizales, Colombia 2 Sapienza University of Rome, Italy Introduction. Ground deformations observed in volcanic areas reflect physics processes that develop at depth and are transmitted to the surface through the mechanical properties of the crust (Dzurisin, 2003). For this reason, monitoring of deformation by Global Positioning System (GPS) and its analysis - together with other geophysical and geochemical monitoring data - are essential to assess the volcanic hazard of a specific area. In this work we present the deformation data recorded at Nevado del Ruiz volcano (Colombia) from 2010 to present and their interpretation. The Nevado del Ruiz Volcanic Complex (NRVC) is part of the North Volcanic Segment of Colombia, a group of eleven volcanoes aligned N-S and extended for 137 km along the highest part of the Central Cordillera of Colombia (San Diego, El Escondido, Romeral, Cerro Bravo, Nevado del Ruiz, Paramillo del Cisne, Nevado de Santa Isabel, Paramillo del Quindio, Paramillo de Santa Rosa, Nevado del Tolima and Cerro Machin). The NRVC has 4 geological stages: the Pre Ruiz effusive volcano 1.8 m.y.b.p.; the 1 st Ruiz effusive stage 1.2 m.y.b.p. with the Rio Claro ignimbrite eruption and a caldera formation; the intermedium stage 89,000 y.b.p with the formation of the La Olleta, La Piraña and Nereidas volcanoes; and the actual Nevado del Ruiz stratovolcano 10,000 y.b.p. with explosive eruptions of a central vent that produced pyroclastic flows and surges, debris avalanches, ash falls and lahars (Martinez, et al. , 2014). Nevado del Ruiz is a 5321 m high dacitic stratovolcano, one of the most active volcanoes of the North Volcanic Complex of Colombia. It is located at 4°53’43”N, 75°19’21”W, near the limits of the departments of Caldas and Tolima, approximately 140 km NW of Bogotá (Capital of Colombia) and 28 km SE of Manizales. On its flat summit lies the main crater called “Arenas” (870 m in diameter and 250 m deep), crowned by an ice cap of about 12 km 2 from where are born the rivers Lagunilla, Azufrado, Guali and Recio that drain into the Magdalena river to the East, and the Molinos, Nereidas and Alfombrales that drain into the Cauca river to the West. Nevado del Ruiz is built on the complex intersection of four fault groups, where the most significant are the Palestine and Termales- Villamaría faults. Fig. 1 - The GPS monitoring network of Nevado del Ruiz Volcano is defined by eight stations (BIS, BLLR, GUAL, NERE, OLLE, RUBI, PIRA and SINN) located around the Volcano.