Mario Fernández

Fluid-volcano interaction in an active stratovolcano: the crater lake system of Poás volcano, Costa Rica

Rowe, G.L. Jr., Brantley, S.L., Fernandez, M., Fernandez, J.F., Borgia, A. and Barquero, J., 1992. Fluid-volcano interaction in an active stratovolcano: the crater lake system of Po~is volcano, Costa Rica. J. Volcanol. Geotherm. Res., 49: 2351. Seismic and geochemical data collected at Po~is volcano, Costa Rica, since 1978 suggest that temperature and chemical variations recorded in subaerial fumaroles and the crater lake are related to episodic release of heat and volatiles associated with hydrofracturing of the upper margin of the shallow magma body. Power outputs associated with these events approach 600 MW and are superimposed on a baseline energy flux of approximately 200 MW. The baseline heat flux suggests a magma solidification rate of 0.012 km3/yr and background volatile release rates of 1000 t/d H20, 66 t/d, S, 13 t/d CI, and 0.5 t/d F. These fluxes are comparable to fluxes of F, C1 and S exiting the magmatic/hydrothermal system through acidic flank springs and are about a factor of five less than estimated volatile fluxes through summit fumaroles during the high-temperature event of 1981-1983. Mass balance considerations suggest that heat released at the lake surface is primarily supplied by the ascent of heated brines supplemented by condensation of fumarolic steam. Calculated average seepage rates out of the lake ( ~ 450 kg/s) indicate rapid convection of acidic lake brine through underlying lake sediments and pyroclastic deposits. Circulation of the extremely corrosive lake brine through the volcanoclastic material beneath the lake may enhance subsurface permeabilities. Fluxes of rock-forming elements observed in the Rio Agrio basin on the northwest flank of Po~is suggest that dissolution and removal of volcano-elastic material occurs at a rate of approximately 1650 m3/yr. However, estimated sulfur fluxes from the cooling magma body suggest that porosity created by this dissolution could quickly be filled by the deposition of native sulfur. Finally,analysis of heat and water budgets for the crater lake over the period 1978-1989 indicates that the recent decline and disappearance of the lake was caused by variations in summit rainfall combined with an increase in subsurface heat flow to the lake in 1987-1988. The increase in heat flow is related to continued degassing of high-temperature volatiles following a hydrofracturing/magma ascent episode that occurred in 1986.

Tsunamis and Tsunami Hazards in Central America

A tsunami catalogue for Central America is compiledcontaining 49 tsunamis for the period 1539–1996,thirty seven of them are in the Pacific and twelve inthe Caribbean. The number of known tsunamis increaseddramatically after the middle of the nineteenth century,since 43 events occurred between 1850 and 1996. This isprobably a consequence of the lack of populationliving near the coast in earlier times.The preliminary regionalization of the earthquakessources related to reported tsunamis shows that, inthe Pacific, most events were generated by theCocos-Caribbean Subduction Zone (CO-CA). At theCaribbean side, 5 events are related with the NorthAmerican-Caribbean Plate Boundary (NA-CA) and 7 withthe North Panama Deformed Belt (NPDB).There are ten local tsunamis with a specific damagereport, seven in the Pacific and the rest in theCaribbean. The total number of casualties due to localtsunamis is less than 455 but this number could behigher. The damages reported range from coastal andship damage to destruction of small towns, and theredoes not exist a quantification of them.A preliminary empirical estimation of tsunami hazardindicates that 43% of the large earthquakes (Ms ≥7.0) along the Pacific Coast of Central America and100% along the Caribbean, generate tsunamis. On thePacific, the Guatemala–Nicaragua coastal segment hasa 32% probability of generating tsunamis after largeearthquakes while the probability is 67% for theCosta Rica–Panama segment. Sixty population centers onthe Pacific Coast and 44 on the Caribbean are exposedto the impact of tsunamis. This estimation alsosuggests that areas with higher tsunami potential inthe Pacific are the coasts from Nicaragua to Guatemalaand Central Costa Rica; on the Caribbean side, Golfode Honduras Zone and the coasts of Panama and CostaRica have major hazard. Earthquakes of magnitudelarger than 7 with epicenters offshore or onshore(close to the coastline) could trigger tsunamis thatwould impact those zones.

Characterization of a photosynthetic Euglena strain isolated from an acidic hot mud pool of a volcanic area of Costa Rica.

Abstract Conspicuous green patches on the surface of an acidic hot mud pool located near the Rincón de la Vieja volcano (northwestern Costa Rica) consisted of apparently unialgal populations of a chloroplast-bearing euglenoid. Morphological and physiological studies showed that it is a non-flagellated photosynthetic Euglena strain able to grow in defined mineral media at temperatures up to 40 degrees C and exhibiting higher thermotolerance than Euglena gracilis SAG 5/15 in photosynthetic activity analyses. Molecular phylogeny studies using 18S rDNA and GapC genes indicated that this strain is closely related to Euglena mutabilis, another acid-tolerant photosynthetic euglenoid, forming a clade deeply rooted in the Euglenales lineage. To our knowledge this is the most thermotolerant euglenoid described so far and the first Euglenozoan strain reported to inhabit acidic hot aquatic habitats.

Tsunami hazard in Central America: history and future

Abstract Central America is a small and culturally homogeneous region that, since the 1990s, has experienced economic and political integration of its six countries, which share the same threats of volcanic eruptions, disastrous earthquakes and tsunamis. The Pacific coastline of 1700 km is common for Guatemala, El Salvador, Honduras, Nicaragua, Costa Rica and Panama, and the Pacific subduction zone has the potential for creating huge tsunamis that threaten this coast. In addition to the natural hazard, the growing tourist industry is expanding its infrastructure along the Pacific beaches, which again enhances the exposure and tsunami risk. Even though the 1992 tsunami disaster in Nicaragua did not severely hit the tourist beaches, it raised the risk awareness, and special attention is now given to ‘slow’ earthquakes that may be modest in shaking while still having a large tsunami potential. The tsunami hazard mapping is well advanced in Nicaragua, Costa Rica and El Salvador, and initiatives are ongoing to improve the mapping in all countries. National systems for early warning were established in Nicaragua and El Salvador, while the other four countries rely on rapid information from the Pacific Tsunami Warning Center. Mitigation measures and information campaigns are presently conducted on a national basis in all countries, but a regional centre for early tsunami warning and coordinated information campaigns (CATAC) is expected to become operational in the near future.

Psychosocial Support to People Affected by the September 5, 2012, Costa Rica Earthquake

The Brigade for psychosocial support in disasters of the University of Costa Rica visited the Nicoya Peninsula (the peninsula where the city of Nicoya is) in September 2012 to give psychosocial support to inhabitants of the area. The population was emotionally affected by an earthquake that took place on September 5 and had traumas, many fears and anguish. The objective of the intervention was to dispel fears and rumors of the population and contribute to the management of the emotions generated by the earthquake. The work included technical presentations on earthquakes and tsunamis, individual support and workshops with children. Found fears include the occurrence of another earthquake, a tsunami, giant landslides and the emergence of an underwater volcano. The communities requested a permanent work of the Brigade in the zone.