Sete Cidades

Photo of this volcano
Google Earth icon
  Google Earth Placemark
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 37.87°N
  • 25.78°W

  • 856 m
    2808 ft

  • 382080
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

The Global Volcanism Program has no activity reports for Sete Cidades.

The Global Volcanism Program has no Weekly Reports available for Sete Cidades.

Index of Monthly Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

09/1998 (BGVN 23:09) Seismic swarm on submarine flank


Contents of Monthly Reports

All information contained in these reports is preliminary and subject to change.

All times are local (= UTC - 1 hour)

09/1998 (BGVN 23:09) Seismic swarm on submarine flank

Since June 1998, increasing seismic activity in the vicinity of Sete Cidades volcano has resulted in occasional seismic swarms. On the night of 2-3 August about 120 events were registered in 3 hours. During that period, five earthquakes were felt along the W coast, the strongest with a magnitude of 3.1 reached a maximum intensity of V (MM) at Ginetes e Varzea. Similarly, on 2 September in Sao Miguel more than 120 events occurred beneath the sea floor over a period of about 4 hours near shore between Ponta da Ferraria and Mosteiros. One of the five felt earthquakes during this period also reached an intensity of V (MM). There were no reports of injury or damage from any of these events.

Information Contacts: João Luis Gaspar (Email: jlgaspar@alf.uac.pt) and Nicolau Wallenstein (Email: nw@mail.telepac.pt), Departamento de Geociencias, Centro de Vulcanologia, Universidade dos Açores, Rua Mae de Deus, 9500 - Ponta Delgada, Sao Miguel, Açores, Portugal.

Sete Cidades volcano at the western end of Sao Miguel Island contains a 5-km-wide summit caldera, occupied by two caldera lakes, that is one of the scenic highlights of the Azores. The steep-walled, 500-m-deep caldera was formed about 22,000 years ago, and at least 22 post-caldera eruptions have occurred. A large group of Pleistocene post-caldera trachytic lava domes, lava flows, and pyroclastic-flow deposits is found on the western-to-northern flanks. A nearly circular ring of six Holocene pyroclastic cones occupies the caldera floor. These have been the source of a dozen trachytic pumice-fall deposits erupted during the past 5000 years. Sete Cidades is one of the most active Azorean volcanoes. Historical eruptions date back to the 15th century and have occurred from within the caldera and from submarine vents off the west coast.

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

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1880 Unknown Confirmed 0 Unknown Volcano Uncertain: submarine vent off Sao Miguel
1861 Unknown Confirmed 0 Unknown Volcano Uncertain: submarine vent off Sao Miguel
1811 Jun 14 1811 Jun 22 Confirmed 3 Historical Observations Submarine vent west of Sete Cidades
1811 Feb 1 1811 Feb 8 Confirmed 2 Historical Observations Submarine vent west of Sete Cidades
1713 Unknown Confirmed 2 Historical Observations West flank (Pico das Camarinhas)
1682 Dec 13 Unknown Confirmed 2 Historical Observations Submarine vent west of Sete Cidades
1638 Jul 3 1638 Jul 28 Confirmed 2 Historical Observations Submarine vent west of Sete Cidades
1444 (?) Unknown Confirmed 4 Historical Observations SW side of caldera (Caldeira Seca)
1110 ± 50 years Unknown Confirmed 2 Radiocarbon (uncorrected) West flank (Ponta de Ferraria)
0950 ± 100 years Unknown Confirmed 2 Radiocarbon (uncorrected) SE flank (Ferraria)
0670 ± 150 years Unknown Confirmed 3 Radiocarbon (uncorrected) SE flank (Carvao)
0380 ± 300 years Unknown Confirmed 4 Tephrochronology SE caldera floor (Lagoa Rasa)
0090 ± 100 years Unknown Confirmed 4 Radiocarbon (uncorrected) SE caldera floor (Lagoa de Santiago)
0750 BCE ± 300 years Unknown Confirmed   Radiocarbon (uncorrected) SE flank (Eguas)
2050 BCE ± 1000 years Unknown Confirmed   Tephrochronology Caldeira do Alfreres and NW flank
3050 BCE (?) Unknown Confirmed 4 Tephrochronology Seara Cerrado da Ladeira

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
Alferes, Caldeira do Cone 450 m 37° 52' 0" N 25° 48' 0" W
Boi, Pico do Cone 542 m 37° 49' 0" N 25° 43' 0" W
Camarinhas, Pico das Cone 219 m 37° 51' 0" N 25° 51' 0" W
Carvao Cone 815 m 37° 49' 0" N 25° 44' 0" W
Cavalo, Pico do Cone 215 m 37° 51' 0" N 25° 51' 0" W
Cedro, Pico do Cone 387 m 37° 49' 0" N 25° 42' 0" W
Cruz, Pico da Cone 850 m 37° 51' 0" N 25° 46' 0" W
Eguas Cone 873 m 37° 50' 0" N 25° 45' 0" W
Enforcado, Pico do Cone 338 m 37° 48' 0" N 25° 41' 0" W
Ferrarias Cone 37° 50' 0" N 25° 46' 0" W
Ilheu Dos Mosteiros Cone 37° 55' 0" N 25° 50' 0" W
Mafra, Pico de Cone 360 m
Mulata Cone 373 m 37° 48' 0" N 25° 42' 0" W
Pilar, Lagoa do Cone 332 m 37° 54' 0" N 25° 47' 0" W
Seara Cerrado de Ladeira Pumice cone 475 m 37° 52' 0" N 25° 48' 0" W
Varzea, Pico do Cone 275 m 37° 52' 0" N 25° 50' 0" W


Craters
Feature Name Feature Type Elevation Latitude Longitude
Alferes, Caldeira do Pumice ring 583 m 37° 52' 0" N 25° 48' 0" W
Canario, Lagoa do Maar 811 m 37° 50' 0" N 25° 46' 0" W
Rasa, Lagoa Pumice ring 625 m 37° 51' 0" N 25° 46' 0" W
Santiago, Lagoa de
    Sao Tiago, Lagoa de
Pumice ring 616 m 37° 51' 0" N 25° 46' 0" W
Scara Pit crater 37° 52' 0" N 25° 48' 0" W
Seca, Caldeira Pumice ring 375 m 37° 51' 0" N 25° 48' 0" W
Both Lagoa Verde (Green Lake) in the foreground and Lagoa Azul (Blue Lake) appear blue in color in this view from the southern rim of the 5-km-wide summit caldera of Sete Cidades volcano on Sao Miguel Island. A nearly circular ring of six Holocene pyroclastic cones occupies the caldera floor. Sete Cidades is one of the most active Azorean volcanoes. Historical eruptions date back to the 15th century and have occurred from within the caldera and from submarine vents off the west coast.

Photo by Rick Wunderman (Smithsonian Institution).
A nearly circular ring of six Holocene pyroclastic cones occupies the floor of 5-km-wide Sete Cidades caldera. These have been the source of a dozen trachytic pumice-fall deposits erupted during the past 5000 years. Three of these forested cones appear in this view from the southern caldera rim, Caldeira Seca (extreme left), Caldeira do Alferes (left-center), and Seara (right center). The cones were constructed on the caldera floor adjacent to the two lakes of Lagoa Azul (top right) and Lagoa Verde (bottom right).

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
The Caldeira Seca pumice ring (center) was formed during a 15th-century explosive eruption through the Sete Cidades caldera lake. A 1444 date is considered the most likely, although dates of 1439 and 1440 are sometimes listed. The Sete L tephra deposit originated from the 600-m-wide, 100-m-deep pumice ring, which is located on the SW floor of the Sete Cidades caldera, whose NE wall forms the horizon.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
The SE floor of Sete Cidades caldera contains a large trachytic lava dome that is cut by two lake-filled craters. The rim of Lagoa de Santiago crater is visible at the center, to the right of the Lagoa Azul and Lagoa Verde lakes occupying the caldera floor. The Lagoa Rasa crater rim appears at the extreme right, below the rim of Sete Cidades caldera. Lagoa de Santiago was the source of a major explosive eruption about 1900 years ago, and Lagoa Rasa erupted several centuries later.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
Caldeira do Alferes (center) is one of a group of six pyroclastic cones constructed on the floor of Sete Cidades caldera. The adjacent cone of Seara appears to the right of Caldeira do Alferes in this view from the western caldera rim. Strong eruptions of trachytic pumice occurred a dozen times during the past 5000 years from Sete Cidades, one of the most active volcanoes of the Azores.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
A small peninsula juts into Lagoa Azul ("Blue Lake"), one of two lakes partially filling the summit caldera on Sete Cidades volcano at the western end of Sao Miguel Island. The 5-km-wide caldera was formed about 22,000 years ago, and at least 22 post-caldera eruptions have occurred. This view looks to the NW from the rim of a post-caldera cone, Caldiera Grande. Two other post-caldera cones, Caldiera do Alfreres and Seara Cerrado da Ladeira, lie across the lake, behind and to the right of the town of Sete Cidades.

Photo by R.V. Fisher, 1980 (University of California Santa Barbara).

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.

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, 1983a. Preliminary geologic map of Sete Cidades volcano, Sao Miguel, Azores (1:18,000). U S Geol Surv Open-File Rpt, 83-742.

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
Pyroclastic cone(s)

Tectonic Setting

Rift zone
Oceanic crust (< 15 km)

Rock Types

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

Population

Within 5 km
Within 10 km
Within 30 km
Within 100 km
3,515
10,365
102,848
127,154

Affiliated Databases

Large Eruptions of Sete Cidades 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.