Busy September for Costa Rican volcanoes

• By Erik Klemetti
• October 4, 2011 |
• 4:56 am

Hard to believe we’ve already entered October, eh?

Some news on volcanic rumblings from Costa Rica:

The summit region of Costa Rica's Rincón de la Vieja in an undated image.

We tend to talk about three volcanoes in Costa Rica: the ever-active Arenal, the renewed Turrialba and Poás. Now we can add another volcano to the watch list, that being Rincón de la Vieja (see above). Like the other Costa Rican volcanoes, it is a composite volcano with overlapping craters at its summit. It is a hulk of a volcano with a total volume of over 130 km³ – and I love that the Global Volcanism Programsummary refers to it as the “Colossus of Guanacaste”. Most of the volcanoes known eruptions have been in the VEI 1-3 range until we get back to ~1820 BC, when a VEI 4 eruption produced pyroclastic flows. The volcano has seen somewhat-persistent fumarolic activity since its last eruptive period in 1995-98 with tremors reported in 2008. However, last month Rincón de la Vieja produced phreatic eruptionsthrough the small lake at the summit crater (see below). During the middle of September, small explosions, ash falls and fish kills were reported at the summit area of Rincón de la Vieja and a visit to the area by OVSICORI scientists revealed 10-15 cm layers of ash – mostly accidental sediment spit back out of the crater lake (pdf in spanish) – in the surrounding area. This new activity has prompted the government to limit access to Rincón de la Vieja and set up a new seismometer north of the volcano.

The crater lake at the summit of Rincón de la Vieja seen in mid-September, 2011. The debris on the edges of the lake were deposited in phreatic (steam-driven) explosions). Image from OVSICORI.

Meanwhile, at Poás, thecrater lake at the summit of that volcano (spanish) has dried up due to the elevated temperatures at the summit fumaroles. When the wind is low, steam plumes from the vigorous fumaroles can be seen in the nearby valleys. There was also an incandescent dome spotted in the last month at the volcano.Turrialba has also seen increase in activity as well. It has been producing light ash falls near the volcano, but theconstant release of volcanic gases such as sulfur dioxide have produced corrosion up to a few kilometers from the vent. Surprisingly, the poster child for Costa Rican volcanoes, Arenal, has been very quite of late, but that doesn’t mean that you can’t find amazing pictures of the volcano, showing the denuded flanks on the volcano mixed with the lush vegetation of the area.

Want to check out some of the activity? There are multiple webcams run by OVSICORI for Arenal, however, it looks like the webcam for Turrialba is out of commission right now. If you know of any other Costa Rica volcano webcams, let us know in the comments below!

Erik Klemetti is an assistant professor of Geosciences at Denison University. His passion in geology is volcanoes, and he has studied them all over the world. You can follow Erik on Twitter, where you'll get volcano news and the occasional baseball comment.
Follow @eruptionsblog on Twitter.

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