Authorities in Colombia have begun to evacuate communities within 15 km of Nevado del Ruiz, 5231 m stratovolcano (cone shaped volcano made up of layers of lava and ash) in the Los Nevados National Natural Park, at the northern end of the Ruiz-Tolima Volcanic Massif. No eruption has been observed on the volcano, but a series of Earthquakes have been recorded beneath it, which can be indicative of magma moving into chambers beneath a volcano, which is a prelude to many eruptions. Nevado del Ruiz is considered particularly dangerous as in 1985 it underwent an eruption which produced 35 million tonnes of volcanic material, including 700 000 tonnes of sulphur dioxide. This in turn triggered a series of lahars that swept to the northwest through a number of local communities, killing over 23 000 people.
The Ruiz-Tolima Volcanic Massif runs north-to-south parallel to the Parallel to the Pacific Coast of Columbia. It is fed by the subduction of the Nazca Plate beneath the South American Plate along the Peru-Chile Tench, which runs approximately parallel to the entire western coast of South America. As the Nazca Plate it sinks into the Earth's interior it is heated by the planet's interior heat. This melts minerals within the subducting plate, some of which then rise through the overlying South American Plate as magma, fueling volcanoes in the Andes along the full extent of the South American west coast.
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