Four volcanoes in Colombia have been placed on raised yellow alert. The volcanoes are Machin, Galeras, Huila, andl Ruiz. Earthquakes increased at Machin volcano on 31st December 2010. Over 4 days 367 volcano-tectonic earthquakes were detected south and southwest of the main dome. The largest event occurred at 5:22 pm on 1st January 2011, with a magnitude 2.3 and a depth of 3.3 km. The earthquake was felt by residents in vicinity of the volcano and in the municipality of Cajamarca (Tolima). In the week from 22 to 28 December 2010, 363 seismic events occurred at Nevado del Huila volcano, of which 72 were related to fracturing of rock and 291 caused by fluid dynamics in volcanic conduits. Nevado del Ruiz and Galeras have showed elevated but stable activity.
Volcanoes of Colombia...