Sete Cidades

Photo of this volcano
  • 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

Most Recent Bulletin Report: September 1998 (BGVN 23:09) Citation IconCite this Report


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.

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

Bulletin Reports - Index


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




Information is preliminary and subject to change. All times are local (unless otherwise noted)


September 1998 (BGVN 23:09) Citation IconCite this Report


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.

Eruptive History


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.

Photo Gallery


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).
See title for photo information.
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).
See title for photo information.
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).
See title for photo information.
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).
See title for photo information.
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).
See title for photo information.
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).
See title for photo information.

Smithsonian Sample Collections Database


There are no samples for Sete Cidades in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites