Nevado del Ruiz

Nevado del Ruiz, also known as La Mesa de Herveo, is an active stratovolcano that is located along the border of the Colombian territories, or departments, of Caldas and Tolima. It reaches an elevation of 17,457 and is shaped like a cone. This volcano is protected within Los Nevados National Natural Park, along with many other volcanoes, and it is a popular tourist destination. Winter activities like skiing are conducted here as well as hiking and fishing.

Nevado del Ruiz is part of the Andes mountains range and one of many volcanoes that comprise the Pacific Ring of Fire. The cone shaped structure of this volcano consists of many layers of tephra, like volcanic ash, and hardened lava and it contains lava made of an andesitic–dacitic mixture. This cone stretches across 77 square miles and holds five lava domes, as well as the Arenas crater, which is 790 feet in depth. Its summit is covered in glaciers that have been retreating since the last glacial maximum, due to atmospheric warming and eruptions. The thickest glaciers, reaching 620 feet in depth, are located on the southwestern slope of the volcano, while some glaciers on northern slopes and other areas only reach a depth of 100 feet. The water that melts off these glaciers feeds the Magdalena and Cauca Rivers and supports forty surrounding towns.

Higher elevations of Nevado del Ruiz hold little tree vegetation and forests become more dense as elevations decrease. Lower elevations hold mesic forests while other areas hold woody plants such as Leguminosa, Melastomataceae, and Lauraceae. Animals that live near the volcano include the rufous-fronted parakeet and the Herveo plump toad, as well as the mountain tapir and spectacled bear, both of which are listed as threatened.

The first eruption of Nevado del Ruiz is thought to have occurred 1.8 million years ago and it underwent three phases from this point known as ancestral, older and present. The present phase began about 150,000 years ago, after which time the current volcano shape was created. Recent eruptions are thought to have occurred between the years of 1570 and 1994, all of which included a central vent eruption and a phreatic (steam) explosion, among other occurrences.  This volcano has a history of causing lahars and pyroclastic flows.

Some of the lahars, or landslides, have been very destructive, including the 1595 lahar that killed over six hundred people and was the result of a major eruption. In 1985, another major eruption occurred that created four large lahars that traveled down the volcano to six river valleys, growing nearly four times their original size. These lahars were devastating, killing over 23,000 people and destroying the city of Armero. This eruption and subsequent mudslides were so destructive because scientists did not understand the volcano and because the chance of an eruption was not taken seriously by many residents and local governments.

Nevado del Ruiz is still active, with recent activity including increased seismic activity near the Arenas crater, phreatic eruptions, a release of sulfurous odors, and earthquakes thought to be pseudo-Tornillo events in 2010. In 2012, ash plumes began emitting from the volcano and after a number of earthquakes, it erupted. Nearby towns were evacuated before this eruption, which lasted until 2013. The biggest threat to over 500,000 inhabitants of the area in the case of another eruption come from landslides, which could be devastating if proper precautions are not taken.

Image Caption: Steam on the mountain in July 2007. Credit: Edgar/Wikipedia (CC BY-SA 2.0)