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.

Concepción is currently the most active composite volcano in Nicaragua. Ash explosions of small to moderate size (volcano explosivity index 1–2) have occurred on a regular basis. Gravity data collected on and around the volcano between 2007 and 2010 confirm that a younger cone is built atop an older truncated edifice of denser material, predominantly lavas. The bulk density of the volcanic cone is 1764 kg m −3 (with an uncertainty of at least ±111 kg m −3 ), derived from gravity data. This estimated bulk density is significantly lower than densities (e.g., 2500 kg m −3 ) used in previous models of gravitational spreading of this volcano and suggests that the gravitational load of the edifice may be much lower than previously thought. The gravity data also revealed the existence of a possible northwest-southeast–oriented normal fault (parallel to the subduction zone). Episodic geodetic data gathered with dual-frequency global positioning system (GPS) instruments at five sites located around the volcano's base show no significant change in baseline length during 8 yr and 2 yr of observations along separate baselines. Structures deformed after the Tierra Blanca Plinian eruption ca. 19 ka, which significantly altered the form and bulk density of the volcano, may be due to the spreading of the volcano, but may also be related to volcano loading, magmatic intrusions and their subsequent evolution, and other volcano-tectonic processes, or a combination of any of these factors. A joint interpretation of our gravity and geodetic GPS data of Concepción suggests that this volcano is not spreading in a continuous fashion; if it is episodically spreading, it is driven by magma intrusion rather than gravity. These results have important implications for volcanic hazards associated with Concepción Volcano. Although during the last 15 yr tephra fallout and volcanic debris flows (lahars) have been the pervasive hazards at this volcano, earthquakes from an eventual slip of the fault on the east-northeast side of the volcano (delineated from our gravity measurements) should be considered as another important hazard, which may severely damage the infrastructures in the island, and conceivably trigger a volcano flank collapse.

Sulfate-rich mineral deposits have been discovered in many locations on Mars through observations by orbiters, landers, and roving spacecraft. It appears that in most cases, these minerals are produced by acid-sulfate weathering of igneous rocks, which may have been a widespread process for the first billion years on Mars. The origin of life on Earth may have occurred in iron-sulfur hydrothermal settings, and early Mars likely had similar environmental conditions. An excellent terrestrial analog for acid-sulfate weathering of Mars-like basalts exists at Cerro Negro, Nicaragua, where acidic sulfur-bearing gases interact with recently erupted basaltic ash in numerous active fumaroles. We investigated the chemistry and mineralogy of the pristine basalts and their chemically weathered products, and we studied the associated microbiological communities as an analog for potential early life on Mars. Measured pH values of condensed volcanic vapors range from −1 to 5, and near-surface temperatures in the fumaroles range from 40 to 400 °C. In a few years, fresh basalt can weather to amorphous silica and gypsum, along with lesser amounts of other sulfates (natroalunite and jarosite), Fe-hydroxides, and clays. Altered rocks have up to 35 wt% SO 3 equivalent, similar to the amounts of sulfur reported for Meridiani Planum bedrocks and inferred in other sulfate-bearing bedrock on Mars. Heavily weathered rocks have silica contents up to 80 wt%, similar to silica-rich soils at Gusev crater that possibly formed in hydrothermal environments. Here, we provide preliminary results of our studies and outline the logistics for a field excursion to this Mars analog system.