Researchers from INETER and FIU visited Telica on 7 March 1994; Mike Conway submitted the following report. In late 1993, INETER deployed a seismic station about 500 m E of the crater, on the crest of an E-W trending ridge. Since the seismic station was deployed, the number of daily seismic events has ranged from 200 to 300. The unusually high seismicity led to concern that Telica was returning to an active phase.

Fumaroles feeding the plume rising from the Telica crater were inaccessible. A small field of passive fumaroles, situated in the E-W trending ridge wall almost immediately below the seismic station, yielded 78-84°C temperatures. These temperatures are similar to the 85°C temperature reported in September for the same fumaroles (BGVN 18:09). Mass flux from the fumaroles, however, appears to have decreased since September 1993. The change in mass flux may be related to seasonal variation in rainfall; the dry season in Nicaragua extends from November through March. Researchers at Telica are currently developing a program to study diffuse gases in soil.

San Jacinto Hot Springs. At the small village of San Jacinto there exist a number of boiling mud pots. San Jacinto is located along Nicaragua Highway 26, about 9 km NE of the town of Telica and 2 km E of Santa Clara volcano. Based on a 9 March 1994 visit by FIU researchers, Mike Conway submitted the following report.

The active mud-pot field measured about 35 x 100 m, elongate N to S. Alteration of basaltic lava flows to the E suggests that the geothermal field was much larger at one time, and probably equidimensional (225 x 225 m).

Individual mud pots ranged in size from 1 m to as much as 3-4 m in diameter. Many of the mud pots were actively spewing mud, and one, located at the SW corner of the field, had, according to local villagers, constructed a mud volcano (to 1-m height) during February-March 1994. For individual mud pots the ratio of mud or muddy water to relatively mud-free water varied. Mud-water temperatures throughout the field, however, were consistent and ranged from 98 to 100°C. These 100°C temperatures were similar to those measured in January 1988 (SEAN 13:01).

Eight soil gas samples, from sites distributed throughout the field, were analyzed for CO₂ using a Hewlett Packard chromatograph. Soil gas CO₂ ranged from 0.04 to 0.09 vol. %, with a mean value of 0.058 vol. % (standard deviation, 0.0184), well within the normal background range of about 0.04-0.1 vol. % typically found in many non-volcanic areas.

Geological Summary. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: Cristian Lugo and Martha Navarro, INETER; Michael Conway, Andrew Macfarlane, and Peter LaFemina, Florida International Univ (FIU); John B. Murray, Ben van Wyk de Vries, and Adam Maciejewski, Open Univ.