Furnas

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  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 37.77°N
  • 25.32°W

  • 805 m
    2640 ft

  • 382100
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Furnas.

The Global Volcanism Program has no Weekly Reports available for Furnas.

The Global Volcanism Program has no Bulletin Reports available for Furnas.

Furnas volcano lies at the eastern end of Sao Miguel Island, immediately west of the older Nordeste shield volcano and its Povoaçao caldera. Furnas contains at least two calderas, a younger one that is 6-km wide and a larger older one that is less topographically distinct. The eastern wall of the 500-m-deep caldera of Furnas overlaps the western wall of the Povoaçao caldera of Nordeste volcano. Volcanic activity at Furnas dates back about 100,000 years. At least 11 trachytic pumice layers, all erupted during the past 5000 years, post-date the caldera. The most prominent post-caldera feature is the Pico do Gaspar lava dome, east of the Lagoa das Furnas caldera lake. A zone of late-Pleistocene to Holocene basaltic-to-trachytic cinder cones and lava domes is located between Furnas and Agua de Pau volcanoes. Two historical eruptions have occurred at Furnas, one sometime between 1439 and 1443 and the other in 1630. The latter was one of the largest Holocene explosive eruptions in the Azores and caused significant damage and fatalities.

Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1630 Sep 3 1630 Nov 2 Confirmed 5 Historical Observations South end of caldera (Pico da Areia)
1441 ± 2 years Unknown Confirmed 4 Historical Observations Center of caldera (Gaspar), Tephra layer I
1430 ± 100 years Unknown Confirmed 3 Radiocarbon (uncorrected) East caldera floor, Tephra layer H
1170 ± 100 years Unknown Confirmed 4 Radiocarbon (uncorrected) E caldera floor (Lake crater), Tephra layer G
0840 ± 100 years Unknown Confirmed 4 Radiocarbon (uncorrected) Center of caldera (Gaspar), Tephra layer F
0080 ± 100 years Unknown Confirmed 5 Radiocarbon (uncorrected) N floor of younger caldera, Tephra layer C
0360 BCE ± 150 years Unknown Confirmed   Radiocarbon (uncorrected) Tephra layer B
1670 BCE ± 1460 years Unknown Confirmed   Tephrochronology Tephra layer A
4570 BCE (in or before) Unknown Confirmed   Radiocarbon (uncorrected) East rim of caldera (Pico do Canário)

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.


Cones

Feature Name Feature Type Elevation Latitude Longitude
Azeitona, Pico da Cone 537 m
Canario, Pico de Pyroclastic cone 615 m 37° 46' 0" N 25° 17' 0" W
Gafanhoto Cone 715 m 37° 47' 0" N 25° 19' 0" W
Nordeste Shield volcano 1105 m 37° 47' 0" N 25° 13' 0" W
Senhora, Pica da Cone 455 m 37° 49' 0" N 25° 20' 0" W

Craters

Feature Name Feature Type Elevation Latitude Longitude
Povoacao Pleistocene caldera 1105 m 37° 46' 0" N 25° 15' 0" W

Domes

Feature Name Feature Type Elevation Latitude Longitude
Areia, Pico Da
    Cova Da Burra
Dome 495 m 37° 44' 0" N 25° 19' 0" W
Buraco, Pico do Dome 702 m
Ferro, Pico do Dome 544 m 37° 46' 0" N 25° 20' 0" W
Gaspar, Pico Do Dome 382 m 37° 45' 0" N 25° 19' 0" W
Marcondas, Pica das
    Murcondas, Pica das
Dome 398 m 37° 46' 0" N 25° 18' 0" W

Thermal

Feature Name Feature Type Elevation Latitude Longitude
Caldieras Thermal
Ribiera Dos Tambores Thermal
The village of Furnas (right) lies in the center of Furnas caldera, whose northern rim forms the ridge in the background. The largest post-caldera Furnas tephra, layer C, originated from a vent where part of the village of Furnas is now located. The eruption was dated at about 2900 years before present. Plinian and sub-plinian eruptions deposited airfall-pumice and -ash, accompanied by local pyroclastic flows and late-stage mudflows.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
The low hill covered by fields (left-center) is Pico do Gaspar lava dome, which lies east of Lagoa das Furnas. Plinian eruptions about 1100 years ago including local pyroclastic flows accompanied formation of two nested pumice rings. An arcuate line of trees about halfway between the lake and the summit of the lava dome marks the rim of the northern pumice ring. The eruption concluded with emplacement of the Pico do Gaspar trachytic lava dome.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
Abundant thermal features exist at Furnas volcano. Some hot springs occur near the caldera lake. This hot spring in the town of Furnas is part of the main fumarole field, which is located in the eastern part of the caldera. The fumarole field contains boiling hot springs and mudpots and is associated with caldera-bounding faults and late-Holocene eruptive vents. A few other fumaroles are located along a gorge of the small river that drains the caldera and on the southern flank, near the coast.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
Furnas volcano, at the eastern end of Sao Miguel Island, contains at least two calderas. The younger 6-km-wide caldera is seen here from its northern rim. At least 11 trachytic pumice layers, all erupted during the past 5000 years, post-date the caldera. A zone of late-Pleistocene to Holocene basaltic-to-trachytic cinder cones and lava domes is located between Furnas and neighboring Agua de Pau volcano. The only historical eruption of Furnas volcano, during 1630, was one of the largest Holocene eruptions in the Azores.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).

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.

Booth B, Croasdale R, Walker G P L, 1978. A quantitative study of five thousand years of volcanism on Sao Miguel, Azores. Phil Trans Roy Soc London, Ser A, 288: 271-319.

Cole P D, Guest J E, Queiroz G, Wallenstein N, Pacheco J-M, Gaspar J L, Ferreira T, Duncan A M, 1999. Styles of volcanism and volcanic hazards on Furnas volcano, Sao Miguel, Azores. J Volc Geotherm Res, 92: 39-53.

Cole P D, Queiroz G, Wallenstein N, Gaspar J L, Duncan A M, Guest J E, 1995. A historic subplinian/phreatomagmatic eruption: the 1630 AD eruption of Furnas volcano, Sao Miguel, Azores. J Volc Geotherm Res, 69: 117-135.

Duncan A M, Queiroz G, Guest J E, Cole P D, Wallenstein N, Pacheco J M, 1999. The Povoacao Ignimbrite, Furnas volcano, Sao Miguel, Azores. J Volc Geotherm Res, 92: 55-65.

Ferreira T, Oskarsson N, 1999. Chemistry and isotopic composition of fumarole discharges of Furnas caldera. J Volc Geotherm Res, 92: 169-179.

Guest J E, Gaspar J L, Cole P D, Queiroz G, Duncan A M, Wallenstein N, Ferreira T, Pacheco J-M, 1999. Volcanic geology of Furnas volcano, Sao Miguel, Azores. J Volc Geotherm Res, 92: 1-29.

Martins J A, 1982. Excursion guide for field trip V1, Island of Sao Miguel. Proc Internatl Symp Activity Oceanic Volc, Archipelago Univ Azores, 3: 315-328.

Moore R B, 1990. Volcanic geology and eruption frequency, Sao Miguel, Azores. Bull Volc, 52: 602-614.

Moore R B, 1991. Geologic map of Sao Miguel, Azores. U S Geol Surv Map, I-2007.

Neumann van Padang M, Richards A F, Machado F, Bravo T, Baker P E, Le Maitre R W, 1967. Atlantic Ocean. Catalog of Active Volcanoes of the World and Solfatara Fields, Rome: IAVCEI, 21: 1-128.

Newhall C G, Dzurisin D, 1988. Historical unrest at large calderas of the world. U S Geol Surv Bull, 1855: 1108 p, 2 vol.

Zbyszewski G, Moitinho de Almeida F, Veiga Ferreira O da, Torre de Assuncao C, 1958. Geologic map of Sao Miguel (Azores). Servicos Geologicos Portugal, two 1:50,000 scale maps with 22 and 37 p texts (in Portuguese).

Volcano Types

Stratovolcano
Caldera(s)
Lava dome(s)
Pyroclastic cone(s)

Tectonic Setting

Rift zone
Oceanic crust (< 15 km)

Rock Types

Major
Trachyte / Trachyandesite
Basalt / Picro-Basalt
Trachybasalt / Tephrite Basanite
Trachyandesite / Basaltic trachy-andesite

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
1,333
7,310
87,865
153,182

Affiliated Databases

Large Eruptions of Furnas 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.