Sometimes it seems as if one of the Search Party finds just as soon as I land at a new volcano..sometimes even before the little stars stop circling my throbbing head. (LI’l Volcanoheads are aerodynamically designed for headfirst descent, but not built quite tough enough to fully withstand sudden stop at fight’s-end). Luckily I have a week-off ahead of me and might actually spend it at home being dormant. A little more on that..but first perhaps you wonder where I’ve been.
This is Galeras, a 4,276 m high stratovolcano in Colombia located just west of the town of Pasto. It has been active for more than a million years and is still one of Colombia’s most active volcanoes. In the late Pleistocene, a pair of caldera collapsing eruptions took place. Those were followed later on by several collapses of the caldera wall, possibly resulting from instability caused by hydrothermal activity, leaving a horseshoe-shaped caldera which partially encloses a younger cone.
Galeras’ frequent eruptions and proximity to the densely populated city of Pasto earned it a place on the list of Decade Volcanoes in 1991. The purpose of the Decade Volcano program was to raise awareness of some of the world’s most dangerous volcanoes and also raise funds for studying their behaviour and developing plans for mitigating disasters. In a sad and ironic twist of fate, it was at one of the Decade Volcano workshops in Pasto in 1993 that a team of scientists ascended to the volcano’s summit despite predictions that the volcano might erupt. The prediction proved accurate, and most of the scientific team were killed.
Observation of Galeras’ behaviour before eruptions has led to at least one interesting discovery. Seismographs recorded peculiar wave patterns that seemed to last several minutes. These waves, unlike regular volcanic tremor, initiate at a higher amplitude, and then decrease in amplitude as the event runs its course. The signatures resemble the profiles of screws and thus are called tornillos after the Spanish word for screw. The frequency of tornillo events as well as size of tornillos not only warns of impending eruption but also seens to correlate to size of explosive eruption.
Also, I have located at least one Galeras webcam.
Congratulations, Jonet “Zola” for finding me so quickly, and also to Jesper for following after her..as well as newcomer George who hopefully will be returning to the Search Party often.
Next week, LI’l Volcanohead will be taking a much-needed rest and a valiant stand-in has offered to lead you all on a special guest-quest. Tune in this coming Monday evening when “Madame Zolcanohead” takes you all (and perhaps me too) on a new adventure at a new volcano.