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Research about Nicaragua

Source-linked reports with geographic coverage including Nicaragua.

12 recordsLinked to original sources
USGS2012

Integrated geophysical and hydrothermal models of flank degassing and fluid flow at Masaya Volcano, Nicaragua

We investigate geologic controls on circulation in the shallow hydrothermal system of Masaya volcano, Nicaragua, and their relationship to surface diffuse degassing. On a local scale (~250 m), relatively impermeable normal faults dipping at ~60° control the flowpath of water vapor and other gases in the vadose zone. These shallow normal faults are identified by modeling of a NE-SW trending magnetic anomaly of up to 2300 nT that corresponds to a topographic offset. Elevated SP and CO2 to the NW of the faults and an absence of CO2 to the SE suggest that these faults are barriers to flow. TOUGH2 numerical models of fluid circulation show enhanced flow through the footwalls of the faults, and corresponding increased mass flow and temperature at the surface (diffuse degassing zones). On a larger scale, TOUGH2 modeling suggests that groundwater convection may be occurring in a 3-4 km radial fracture zone transecting the entire flank of the volcano. Hot water rising uniformly into the base of the model at 1 x 10-5 kg/m2s results in convection that focuses heat and fluid and can explain the three distinct diffuse degassing zones distributed along the fracture. Our data and models suggest that the unusually active surface degassing zones at Masaya volcano can result purely from uniform heat and fluid flux at depth that is complicated by groundwater convection and permeability variations in the upper few km. Therefore isolating the effects of subsurface geology is vital when trying to interpret diffuse degassing in light of volcanic activity.

Masaya Volcano↗
USGS2011

Integrating occupancy modeling and interview data for corridor identification: A case study for jaguars in Nicaragua

Corridors are critical elements in the long-term conservation of wide-ranging species like the jaguar ( Panthera onca ). Jaguar corridors across the range of the species were initially identified using a GIS-based least-cost corridor model. However, due to inherent errors in remotely sensed data and model uncertainties, these corridors warrant field verification before conservation efforts can begin. We developed a novel corridor assessment protocol based on interview data and site occupancy modeling. We divided our pilot study area, in southeastern Nicaragua, into 71, 6 × 6 km sampling units and conducted 160 structured interviews with local residents. Interviews were designed to collect data on jaguar and seven prey species so that detection/non-detection matrices could be constructed for each sampling unit. Jaguars were reportedly detected in 57% of the sampling units and had a detection probability of 28%. With the exception of white-lipped peccary, prey species were reportedly detected in 82–100% of the sampling units. Though the use of interview data may violate some assumptions of the occupancy modeling approach for determining ‘proportion of area occupied’, we countered these shortcomings through study design and interpreting the occupancy parameter, psi, as ‘probability of habitat used’. Probability of habitat use was modeled for each target species using single state or multistate models. A combination of the estimated probabilities of habitat use for jaguar and prey was selected to identify the final jaguar corridor. This protocol provides an efficient field methodology for identifying corridors for easily-identifiable species, across large study areas comprised of unprotected, private lands.

Biological Conservation↗
USGS2008

Rapid response of a hydrologic system to volcanic activity: Masaya volcano, Nicaragua

Hydrologic systems change in response to volcanic activity, and in turn may be sensitive indicators of volcanic activity. Here we investigate the coupled nature of magmatic and hydrologic systems using continuous multichannel time series of soil temperature collected on the flanks of Masaya volcano, Nicaragua, one of the most active volcanoes in Central America. The soil temperatures were measured in a low-temperature fumarole field located 3.5 km down the flanks of the volcano. Analysis of these time series reveals that they respond extremely rapidly, on a time scale of minutes, to changes in volcanic activity also manifested at the summit vent. These rapid temperature changes are caused by increased flow of water vapor through flank fumaroles during volcanism. The soil temperature response, ~5 °C, is repetitive and complex, with as many as 13 pulses during a single volcanic episode. Analysis of the frequency spectrum of these temperature time series shows that these anomalies are characterized by broad frequency content during volcanic activity. They are thus easily distinguished from seasonal trends, diurnal variations, or individual rainfall events, which triggered rapid transient increases in temperature during 5% of events. We suggest that the mechanism responsible for the distinctive temperature signals is rapid change in pore pressure in response to magmatism, a response that can be enhanced by meteoric water infiltration. Monitoring of distal fumaroles can therefore provide insight into coupled volcanic-hydrologic-meteorologic systems, and has potential as an inexpensive monitoring tool.

Masaya Volcano↗
USGS2006

The A.D. 1835 eruption of Volcán Cosigüina, Nicaragua: A guide for assessing local volcanic hazards

The January 1835 eruption of Volcán Cosigüina in northwestern Nicaragua was one of the largest and most explosive in Central America since Spanish colonization. We report on the results of reconnaissance stratigraphic studies and laboratory work aimed at better defining the distribution and character of deposits emplaced by the eruption as a means of developing a preliminary hazards assessment for future eruptions. On the lower flanks of the volcano, a basal tephra-fall deposit comprises either ash and fine lithic lapilli or, locally, dacitic pumice. An overlying tephra-fall deposit forms an extensive blanket of brown to gray andesitic scoria that is 35–60 cm thick at 5–10 km from the summit-caldera rim, except southwest of the volcano, where it is considerably thinner. The scoria fall produced the most voluminous deposit of the eruption and underlies pyroclastic-surge and -flow deposits that chiefly comprise gray andesitic scoria. In northern and southeastern sectors of the volcano, these flowage deposits form broad fans and valley fills that locally reach the Gulf of Fonseca. An arcuate ridge 2 km west of the caldera rim and a low ridge east of the caldera deflected pyroclastic flows northward and southeastward. Pyroclastic flows did not reach the lower west and southwest flanks, which instead received thick, fine-grained, accretionary-lapilli–rich ashfall deposits that probably derived chiefly from ash clouds elutriated from pyroclastic flows. We estimate the total bulk volume of erupted deposits to be ∼6 km 3 . Following the eruption, lahars inundated large portions of the lower flanks, and erosion of deposits and creation of new channels triggered rapid alluviation. Pre-1835 eruptions are poorly dated; however, scoria-fall, pyroclastic-flow, and lahar deposits record a penultimate eruption of smaller magnitude than that of 1835. It occurred a few centuries earlier—perhaps in the fifteenth century. An undated sequence of thick tephra-fall deposits on the west flank of the volcano records tens of eruptions, some of which were greater in magnitude than that of 1835. Weathering evidence suggests this sequence is at least several thousand years old. The wide extent of pyroclastic flows and thick tephra fall during 1835, the greater magnitude of some previous Holocene eruptions, and the location of Cosigüina on a peninsula limit the options to reduce risk during future unrest and eruption.

GSA Special Papers↗
USGS2005

Comparative soil CO2 flux measurements and geostatistical estimation methods on Masaya volcano, Nicaragua

We present a comparative study of soil CO 2 flux ( F C O 2 "> F C O 2 ) measured by five groups (Groups 1–5) at the IAVCEI-CCVG Eighth Workshop on Volcanic Gases on Masaya volcano, Nicaragua. Groups 1–5 measured F C O 2 using the accumulation chamber method at 5-m spacing within a 900 m 2 grid during a morning (AM) period. These measurements were repeated by Groups 1–3 during an afternoon (PM) period. Measured F C O 2 ranged from 218 to 14,719 g m −2 day −1 . The variability of the five measurements made at each grid point ranged from ±5 to 167%. However, the arithmetic means of fluxes measured over the entire grid and associated total CO 2 emission rate estimates varied between groups by only ±22%. All three groups that made PM measurements reported an 8–19% increase in total emissions over the AM results. Based on a comparison of measurements made during AM and PM times, we argue that this change is due in large part to natural temporal variability of gas flow, rather than to measurement error. In order to estimate the mean and associated CO 2 emission rate of one data set and to map the spatial F C O 2 distribution, we compared six geostatistical methods: arithmetic and minimum variance unbiased estimator means of uninterpolated data, and arithmetic means of data interpolated by the multiquadric radial basis function, ordinary kriging, multi-Gaussian kriging, and sequential Gaussian simulation methods. While the total CO 2 emission rates estimated using the different techniques only varied by ±4.4%, the F C O 2 maps showed important differences. We suggest that the sequential Gaussian simulation method yields the most realistic representation of the spatial distribution of F C O 2 , but a variety of geostatistical methods are appropriate to estimate the total CO 2 emission rate from a study area, which is a primary goal in volcano monitoring research.

Masaya↗
USGS2004

Lahar Hazards at Casita and San Cristóbal Volcanoes, Nicaragua

Casita and San Cristóbal volcanoes are part of a volcano complex situated at the eastern end of the Cordillera de los Maribios. Other centers of volcanism in the complex include El Chonco, Cerro Moyotepe, and La Pelona. At 1745 m, San Cristóbal is the highest and only historically active volcano of the complex. The volcano’s crater is 500 to 600 m across and elongate east to west; its western rim is more than 100 m higher than its eastern rim. The conical volcano is both steep and symmetrical. El Chonco, which lies west of San Cristóbal, is crudely conical but has been deeply dissected by streams. Cerro Moyotepe to the northeast of San Cristóbal is even more deeply incised by erosion than El Chonco, and its crater is breached by erosion. Casita volcano, about 5 km east of San Cristóbal volcano, comprises a broad ridge like form, elongate along an eastwest axis, that is deeply dissected. Nested along the ridge are two craters. The younger one, La Ollada crater, truncates an older smaller crater to the east near Casita’s summit (1430 m). La Ollada crater is about 1 km across and 100 m deep. Numerous small fumarole fields occur near the summit of Casita and on nearby slopes outside of the craters. Casita volcano overlaps the 3-km-wide crater of La Pelona to the east. Stream erosion has deeply incised the slopes of La Pelona, and it is likely the oldest center of the Casita-San Cristóbal volcano complex. In late October and early November 1998, torrential rains of Hurricane Mitch caused numerous slope failures in Central America. The most catastrophic occurred at Casita volcano, on October 30, 1998. At Casita, five days of heavy rain triggered a 1.6-million-cubic-meter rock and debris avalanche that generated an 2- to 4- million-cubic-meter debris flow that swept down the steep slopes of the volcano. The debris flow spread out across the volcano’s apron, destroyed two towns, and killed more than 2500 people. In prehistoric time, Casita erupted explosively to form ash-fall deposits (tephra), debris avalanches, lava flows, and hot flowing mixtures of ash and rock (called pyroclastic flows). The chronology of activity at Casita is rather poorly known. Its last documented eruption occurred 8300 years ago, and included a pyroclastic flow. Tephra deposits exposed in the east crater suggest the possibility of subsequent eruptions. Work prior to Hurricane Mitch suggested that a part of the volcano’s apron that included the area inundated during the 1998 event south of Casita was a lahar pathway. Erosion during Hurricane Mitch revealed that at least three large lahars descended this pathway to distances of up to 10 km. This report describes the hazards of landslides and lahars in general, and discusses potential hazards from future landslides and lahars at San Cristóbal and Casita volcanoes in particular. The report also shows, in the accompanying lahar hazard-zonation maps, which areas are likely to be at risk from future landslides and lahars at Casita and San Cristóbal.

Open-File Report↗
USGS2001

Lahar hazards at Mombacho Volcano, Nicaragua

Mombacho volcano, at 1,350 meters, is situated on the shores of Lake Nicaragua and about 12 kilometers south of Granada, a city of about 90,000 inhabitants. Many more people live a few kilometers southeast of Granada in 'las Isletas de Granada and the nearby 'Peninsula de Aseses. These areas are formed of deposits of a large debris avalanche (a fast moving avalanche of rock and debris) from Mombacho. Several smaller towns with population, in the range of 5,000 to 12,000 inhabitants are to the northwest and the southwest of Mombacho volcano. Though the volcano has apparently not been active in historical time, or about the last 500 years, it has the potential to produce landslides and debris flows (watery flows of mud, rock, and debris -- also known as lahars when they occur on a volcano) that could inundate these nearby populated areas. -- Vallance, et.al., 2001

Granada↗
USGS1981

Quiet zone within a seismic gap near western Nicaragua: Possible location of a future large earthquake

A 5700-square-kilometer quiet zone occurs in the midst of the locations of more than 4000 earthquakes off the Pacific coast of Nicaragua. The region is indicated by the seismic gap technique to be a likely location for an earthquake of magnitude larger than 7. The quiet zone has existed since at least 1950; the last large earthquake originating from this area occurred in 1898 and was of magnitude 7.5. A rough estimate indicates that the magnitude of an earthquake rupturing the entire quiet zone could be as large as that of the 1898 event. It is not yet possible to forecast a time frame for the occurrence of such an earthquake in the quiet zone.

western Nicaragua↗