• By Erik Klemett
• It wasn’t too long ago that Galeras was the only show in town in Colombia. After Nevado del Ruiz settled from its eruptions during the 1980s, there wasn’t much other volcanic activity in the South American nation than the ever-active Galeras near Pasto. However, now it seems that more volcanoes are getting the attention of the INGEOMINAS (the Colombian Geological Survey). With all this news of Colombian volcanoes, I thought I’d offer a brief tour of the action. Remember, Colombia has a few dozen potentially active volcanoes, so this activity shouldn’t be too surprising. You can check out this page to see what each of the INGEOMINAS alert status mean.

A webcam capture of the June 30, 2012 eruption of Nevado del Ruiz in Colombia. Most of the volcano is obscured by clouds, but the grey-brown ash plume spread ash across the countryside. Image courtesy of INGEOMINAS.

Nevado del Ruiz

After an almost 2o year slumber, Nevado del Ruiz has sprung back to life this year, with multiple small, ashy explosions (see above) and constant seismicity that might be leading to more vigorous eruptions (or might not). A few thousand people have needed to evacuate the slopes of the snow-covered volcanoes, mostly due to the threat of lahars generated by these explosions and rapid melting of snow and ice at the summit. Ash continues to fall on areas around the volcano as the activity waxes and wanes as well. The latest update from INGEOMINAS on the activity at Ruiz has the volcano at Orange Level II status, meaning eruptions should be expected in days to weeks.

Machín

Machín, a neighbor of Ruiz, has also seen elevated levels of seismicity over the past few years. Nothing has occurred beyond earthquakes that suggest rock fracturing  that could be hydrothermal or magma movement under the volcano. Machín hasn’t erupted in over 1100 years and not much is known about the dome complex that sits within a 3-km caldera. INGEOMINAS currently has the volcano at Yellow Alert III due to the continued seismicity.

Huila

After over 450 years of quiet, Nevado del Huila came back to life in 2008 with a series of small explosions that has produced ash falls, lahars and lava domes at the summit of the volcano (totally a VEI 3 eruption so far). The eruption is considered to be ongoing, although right now the volcano is merely steaming from fumaroles at the summit and experienced tens to hundreds of small earthquakes each week. Huila currently sits at Yellow Alert III.

The steaming summit of Cumbal seen on August 1, 2010. Fumarolic activity such as this is common at Cumbal, but increased seismicity has prompted an increase in the alert level. Image courtesy of INGEOMINAS.

Cumbal

The latest volcano to join the parade of elevated activity is Cumbal (see above), a composite volcano that last erupted in 1926. A report that was issued yesterday (July 11) from INGEOMINAS has raised the alert status to Yellow Alert III after noticing increases in earthquake swarms under the volcano, along with an increase in the temperature of fumaroles at the summit of Cumbal. There has also been reports of noises coming from the volcano in the past few week as well. Much like Machín, not much is known about Cumbal, with only one other known eruption (in 1877). However, Cumbal has rumbled before without producing any eruption.

Sotará

Even less is known about Sotará, a small volcano near Popayán. There have been no known historic eruptions of Sotará, however in late June, seismometers recorded a swarm of over 900 small earthquakes under the volcano. INGEOMINAS did not raise the alert status for Sotará after the swarm, and the swarm seems to be very transitory in nature – not much activity before and after the June 30 swarm.

Galeras

The southernmost volcano in Colombia, Galeras continues to sit at Yellow Alert III. The volcano has not been as eruptively active over the last few months than in recent years, but seismicity continues as does sulfur dioxide emissions. INGEOMINAS describes the current activity as “a reflection of an evolving process that initiated mainly by the intrusion of magmatic material that began to emerge in mid-March 2012″ – that suggests a period of slow dome growth at Galeras right now.

Does all this activity mean that volcanism is on the rise in Colombia? Probably not – in fact, this might be a great case on how increased volcano monitoring helps us become more aware of how restless volcanoes can be when they aren’t erupting or about to erupt. Many of the volcanoes on Yellow Alert III status, like Cumbal and Machin, are only experiencing earthquakes are no one on the surface would even notice. So before many of these volcanoes were wired with seismometers, they could have experienced activity like this and no one would notice. The same can be said for volcanoes worldwide – we can capture so much more subtle information about volcanic activity today than we could even 15 years ago. This can give that false impression that there is more volcanic activity, but rather, we’re just getting more information about what volcanoes do all the time.

from:    http://www.wired.com/wiredscience/2012/07/the-volcanoes-of-colombia-more-active-or-just-more-watched/#more-120011