Santo Tomás

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 14.71°N
  • 91.479°W

  • 3542 m
    11618 ft

  • 342800
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Santo Tomás.

The Global Volcanism Program has no Weekly Reports available for Santo Tomás.

The Global Volcanism Program has no Bulletin Reports available for Santo Tomás.

Volcán Santo Tomás (also known as Volcán Pecul) is a large eroded stratovolcano located across a valley SE of Santa María volcano. The summit of the volcano is capped by late-Quaternary andesitic tephra. A winding ridge connects Santo Tomás to Volcán de Zunil, 4.5 km to the NE, a 3542-m-high stratovolcano that forms the topographic high point of the Santo Tomás - Zunil complex. Volcán de Zunil is located on the SW rim of the 4-km-wide, 600-m-deep Tzanjuyub caldera, which is breached to the south by the Río Masa. Several dacitic-rhyolitic lava domes are located on the caldera's northern flank and the NW flank of Volcán de Zunil. The youngest dome, Cerro Zunil, was last active about 84,000 years ago (K-Ar dating). No Holocene eruptions are known from Santo Tomás, although it was included in the Catalog of Active Volcanoes of the World (Mooser et al., 1958) based on its geothermal activity. Solfataras and thermal springs are located on the west side of the ridge between Santo Tomás and Zunil.

The Global Volcanism Program is not aware of any Holocene eruptions from Santo Tomás. If this volcano has had large eruptions (VEI >= 4) prior to 10,000 years ago, information might be found on the Santo Tomás page in the LaMEVE (Large Magnitude Explosive Volcanic Eruptions) database, a part of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.



Synonyms
Pecul, Volcán | Santo Tomás - Zunil


Craters
Feature Name Feature Type Elevation Latitude Longitude
Tzanjuyub Pleistocene caldera 3542 m 14° 46' 0" N 91° 26' 0" W


Domes
Feature Name Feature Type Elevation Latitude Longitude
Chiucham, Cerro Dome 3278 m 14° 47' 2" N 91° 26' 6" W
Chonajtajuyub, Cerro Dome 2947 m 14° 46' 59" N 91° 26' 46" W
Jolom, Cerro Dome 2890 m 14° 47' 49" N 91° 26' 6" W
Zunil Dome 3542 m 14° 44' 20" N 91° 27' 0" W


Thermal
Feature Name Feature Type Elevation Latitude Longitude
Aguas Amargas Thermal
Volcán Santo Tomás is a Pleistocene stratovolcano with a large erosional caldera breached to the south. The complex volcano is seen here from the summit of Santa María volcano to its NW. Several lava domes are located on the volcano's flanks. No Holocene eruptions are known, although solfatara fields are located 3 km north and NW of the 3542-m-high summit of Volcán Zunil (right), which is located at the southern end of the volcanic complex. The volcano pairs of Tolimán-Atitlán and Acatenango-Fuego appear in the distance.

Photo by Lee Siebert, 1993 (Smithsonian Institution).
Volcán Santo Tomás (also known as Pecul) is the sharp peak on the right-center horizon rising above the Pacific coastal plain. A winding ridge connects Santo Tomás to Volcán de Zunil, 4.5 km to the NE, a 3542-m-high stratovolcano that forms the topographic high point of the complex at the extreme right. No Holocene eruptions are known from Santo Tomás, although there are active solfatara fields. An eruption plume rises from Santiaguito lava dome on the flank of conical Santa María volcano, across the Río Samalá to the west.

Photo by Lee Siebert, 1988 (Smithsonian Institution).
Conical Volcán Atitlán rises 3500 m above the flat-lying Pacific coastal plain of Guatemala. Atitlán's twin volcano to the north, Tolimán, forms the shoulder to the right of the summit. The volcanic highlands of Guatemala are seen here from the SE with Volcán Santo Tomás (Pecul) on the far left horizon, 35 km to the NW of Atitlán volcano.

Photo by Lee Siebert, 1988 (Smithsonian Institution).
The forested Cerro Quemado lava dome (left), seen here from Siete Orejas volcano, is one of a series of dacitic and rhyolitic lava domes constructed along the margin of the Almolonga caldera. The central dome complex of Cerro Quemado was erupted during the Holocene from at least 8 vents arranged in a circular pattern. One of these flank vents forms the low rounded ridge below the center horizon. Santa María volcano lies just out of view to the right, and the western side of the Santo Tomás (Pecul) volcanic complex forms the horizon.

Photo by Bill Rose, 1975 (Michigan Technological University).
Volcán Santo Tomás (also known as Volcán Pecul) is a large eroded stratovolcano that rises here to the east across the valley of the Río Samalá from the Zunil geothermal site. A winding ridge connects Santo Tomás to Volcán de Zunil, 4.5 km to the NE, a 3542-m-high stratovolcano that forms the topographic high point of the complex. No Holocene eruptions are known from Santo Tomás, although solfatara fields are located on the NW flank and 3 km north along the ridge to Zunil.

Photo by Bill Rose, 1981 (Michigan Technological University).
This view looks to the south from near the summit of Volcán de Zunil towards Volcán Santo Tomás (Pecul). Solfatara fields are located along the ridge between Santo Tomás and Zunil. Volcán de Zunil is located on the SW rim of the 4-km-wide, 600-m-deep Tzanjuyub caldera, which is breached to the south by the Río Masa.

Photo by Bill Rose, 1977(Michigan Technological University).
The light-colored, furrowed area at the top-center is the 4-km-wide, 600-m-deep Tzanjuyub caldera, which is breached to the south by the Río Masa. At the SW side of the Pleistocene caldera is Volcán Zunil, which is connected by an irregular ridge to Volcán Santo Tomás, a large eroded stratovolcano above the clouds at the bottom of the image. Santa María volcano (far left-center) lies across the Río Samalá to the east. Solfataras and thermal springs are located on the west side of the ridge between Santo Tomás and Zunil.

NASA Landsat image, 2000 (courtesy of Loren Siebert, University of Akron).

The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.

Carr M J, Rose W I Jr, 1987. CENTAM; a database of Central American volcanic rocks. J Volc Geotherm Res, 33: 239-240.

Hughes J M, 1978. Geology and petrology of the Caldera Tzanjuyub, western Guatemala. Unpublished Master's thesis, Dartmouth College, 123 p.

Hughes J M, Stoiber R E, Ide G M, Maynard S R, Mackay A M, 1980. Quaternary volcanism east of the Zunil Fault Zone, west Guatemala (abs). Eos, Trans Amer Geophys Union, 61: 69.

Katsui Y (ed), 1971. List of the World Active Volcanoes. Volc Soc Japan draft ms, (limited circulation), 160 p.

Mooser F, Meyer-Abich H, McBirney A R, 1958. Central America. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 6: 1-146.

Newhall C G, 1987. Geology of the Lake Atitlan region, western Guatemala. J Volc Geotherm Res, 33: 23-55.

Rose W I, 1987b. Volcanic activity at Santiaguito volcano, 1976-1984. Geol Soc Amer Spec Pap, 212: 17-27.

Williams H, Meyer-Abich H, 1955. Volcanism in the southern part of El Salvador with particular reference to the collapse basins of Lakes Coatepeque and Ilopango. Univ Calif Pub Geol Sci, 32: 1-64.

Volcano Types

Stratovolcano(es)
Caldera
Lava dome(s)

Tectonic Setting

Subduction zone
Continental crust (> 25 km)

Affiliated Databases

Large Eruptions of Santo Tomás Information about large Quaternary eruptions (VEI >= 4) is cataloged in the Large Magnitude Explosive Volcanic Eruptions (LaMEVE) database of the Volcano Global Risk Identification and Analysis Project (VOGRIPA).
WOVOdat WOVOdat is a database of volcanic unrest; instrumentally and visually recorded changes in seismicity, ground deformation, gas emission, and other parameters from their normal baselines. It is sponsored by the World Organization of Volcano Observatories (WOVO) and presently hosted at the Earth Observatory of Singapore.
EarthChem EarthChem develops and maintains databases, software, and services that support the preservation, discovery, access and analysis of geochemical data, and facilitate their integration with the broad array of other available earth science parameters. EarthChem is operated by a joint team of disciplinary scientists, data scientists, data managers and information technology developers who are part of the NSF-funded data facility Integrated Earth Data Applications (IEDA). IEDA is a collaborative effort of EarthChem and the Marine Geoscience Data System (MGDS).
Smithsonian Collections Search the Smithsonian's NMNH Department of Mineral Sciences collections database. Go to the "Search Rocks and Ores" tab and use the Volcano Name drop-down to find samples.