OVSICORI-UNA reports the return of Laguna Caliente, the hyper-acidic crater lake of Poás volcano, Costa Rica, as shown in the web-cam view below (top picture, http://www.ovsicori.una.ac.cr/index.php/vulcanologia/camaras-volcanes/crater-v-poas).
The crater lake had disappeared after culmination of the 2006-2016 phreatic eruption cycle into phreatomagmatic and magmatic eruptions, activity that started in April 2017. The southern part of the basin of Laguna Caliente (front of the top picture below) was newly formed after the 2017 magmatic eruptions that destroyed the dome, emplaced during the last major magmatic eruption cycle of 1953-1955 (lower picture).
It is no surprise that Laguna Caliente reformed, as the large volume magmatic-hydrothermal system underlying the lake was probably only temporarily and partially disturbed by the magmatic eruptions in 2017.
A recent paper by Terada and Hashimoto (2017) (Variety and sustainability of volcanic lakes: Response to subaqueous thermal activity predicted by a numerical model, J Geophys Res Solid Earth 122.doi:10.1002/2017JB14387) explains that neither a high rate of precipitation nor an impermeable layer at the lake bottom are necessary constraints to sustain/reform an active crater lake; a sufficiently high ratio between input rate at the lake bottom of a high enthalpy fluid and the lake surface can cause the re-appearance of a crater lake.
The adequate lake basin, abundant rain fall, and high fluid input from below are all factors favoring lake formation. As such, the Poás crater has returned to its most characteristic “wet” nature, hosting Laguna Caliente. The new peanut-shaped “window” into the magmatic-hydrothermal will be a useful tool for future monitoring efforts. OVSICORI and RSN-UCR will follow up the monitoring of Laguna Caliente with remote sensing techniques, direct measurements and lake and fumarole sampling, following internal safety protocols.
20 January 2018 (OVSICORI web-cam: http://www.ovsicori.una.ac.cr/index.php/vulcanologia/camaras-volcanes/crater-v-poas)
April 2007 (D. Rouwet)
The state of activity during the past year can be tracked on http://www.ovsicori.una.ac.cr/index.php/vulcanologia/grafica-de-los-volcanes, or http://www.rsn.ucr.ac.cr/actividad-volcanica/reportes-volcanicos#
FURTHER READING on arguably the most studied crater lake on Earth:
Recent publications on the 2006-2016 phreatic eruption cycle are:
- de Moor JM, Aiuppa A, Pacheco J, Avard G, Kern C, Liuzzo M, Martínez M, Giudice G, Fischer TP (2016) Short-period volcanic gas precursors to phreatic eruptions: Insights from Poás Volcano, Costa Rica. Earth Planet Sci Lett 442:218-227.doi:10.1016/J.epsl.2016-02-056
- Fischer TP, Ramírez C, Mora-Amador RA, Hilton DR, Barnes JD, Sharp ZD, de Moor JM, Barry PH, Füri E, Shaw AM (2015) Temporal variations in fumarole gas chemistry at Poás volcano, Costa Rica. J Volcanol Geotherm Res 294:56-70.doi:10.1016/j.volgeores.2015.02.002
- Rouwet D, Mora-Amador R, Ramírez CJ, González G, Inguaggiato S (2016) Dynamic fluid recycling at Laguna Caliente (Poás, Costa Rica) before and during the 2006-ongoing phreatic eruption cuycle. Geological Society of London Special Publications 437, Geochemistry and Geophysics of Volcanic Lakes. Eds. Caudron C, Capaccioni B, Ohba T.doi:10.1144/SP437.11
Poás’ Laguna Caliente on 22 January 2018 (picture by Carlos Cordero).
IAVCEI Commission on Volcanic lakes 