Report on Momotombo (Nicaragua) — April 1995
Bulletin of the Global Volcanism Network, vol. 20, no. 4 (April 1995)
Managing Editor: Richard Wunderman
Momotombo (Nicaragua) Fumarole chemistry and temperature data for 1983 and 1995
Please cite this report as:
Global Volcanism Program, 1995. Report on Momotombo (Nicaragua). In: Wunderman, R (ed.), Bulletin of the Global Volcanism Network, 20:4. Smithsonian Institution. http://dx.doi.org/10.5479/si.GVP.BGVN199504-344090.
12.422°N, 86.54°W; summit elev. 1297 m
All times are local (unless otherwise noted)
On 25 February 1995 Lucano Giannini and Orlando Vaselli (University of Florence) visited the crater of Momotombo to collect fumarolic gas samples. The chemical composition of the gases at the highest observed temperature is shown on table 4. Also shown for comparison are values obtained in 1983, when seismic activity, ground deformation, and subsurface basaltic magma emplacement took place. The temperature decrease and gas compositional changes were thought to mainly reflect the twelve years of cooling.
Table 4. Chemical analyses on Momotombo fumaroles, 1983 and 1995. Courtesy of Marino Martini, University of Florence.
|H2O (volume %)||94.00||91.18|
|CO2 (dry gas %)||56.95||72.79|
|SO2 (dry gas %)||22.33||8.72|
|H2S (dry gas %)||5.00||3.87|
|HCl (dry gas %)||5.83||6.25|
|HF (dry gas %)||0.30||0.36|
|B (dry gas %)||0.081||0.018|
|Br (dry gas %)||0.0088||0.0073|
|NH4 (dry gas %)||0.0088||0.0038|
|H2 (dry gas %)||8.47||5.12|
|N2 (dry gas %)||0.78||2.73|
|CO (dry gas %)||0.25||0.12|
Geologic Background. Momotombo is a young, 1297-m-high stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows from Momotombo have flowed down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms a 391-m-high island offshore in Lake Managua. Momotombo has a long record of strombolian eruptions, punctuated by occasional larger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after an April 10, 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the southern flank of the volcano.
Information Contacts: Marino Martini, University of Florence, Italy.