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Sete Cidades

Photo of this volcano
  • Portugal
  • Atlantic Ocean
  • Stratovolcano
  • 1880 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 37.865°N
  • 25.785°W

  • 842 m
    2762 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 and Nicolau Wallenstein, 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 and Nicolau Wallenstein, Departamento de Geociencias, Centro de Vulcanologia, Universidade dos Açores, Rua Mae de Deus, 9500 - Ponta Delgada, Sao Miguel, Açores, Portugal.

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.

Eruptive History

There is data available for 16 Holocene eruptive periods.

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
Deformation History

There is no Deformation History data available for Sete Cidades.

Emission History

There is no Emissions History data available for Sete Cidades.

Photo Gallery

The 5-km-wide Sete Cidades caldera, seen from the southern rim, with lakes Lagoa Verde (foreground) and Lagoa Azul (background) that occupy much of the central caldera floor. To the east (right) and west (left) of these lakes are several pyroclastic cones that have formed in explosive eruptions during the last 5,000 years.

Photo by Rick Wunderman (Smithsonian Institution).
The summit caldera of Sete Cidades volcano at the western end of Sao Miguel Island contains two lakes and is one of the scenic highlights of the Azores. A nearly circular ring of six Holocene pyroclastic cones occupies the floor of the 5-km-wide caldera and has been the source of a dozen major explosive eruptions 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.

Copyrighted photo by Katia and Maurice Krafft, 1980.
A highway bridge spans the junction of Lagoa Verde (left) and Lagoa Azul (right) lakes on the floor of Sete Cidades caldera. The erosionally furrowed wall of Caldeira Seca, the youngest of a circular group of post-caldera pyroclastic cones constructed within 5-km-wide Sete Cidades caldera, rises beyond the two lakes. The town of Sete Cidades (upper right) occupies the caldera floor between Caldeira Seca and another youthful pumice cone, Caldeira do Alferes.

Copyrighted photo by Katia and Maurice Krafft, 1980.
This 19th-century sketch shows a submarine eruption during 1811 off the western coast of Sao Miguel Island in the Azores. Lightning flashes appear at the base of the eruption column, which consists of both a light-colored steam cloud and a darker, ash-laden eruption plume. Explosive eruptions took place February 1-8 and June 16-22, 1811 from the submarine vent. The June eruptions formed an ephemeral island named Sabrina that at its peak stage of growth was 2-km long and 90-m high.

From the collection of Maurice and Katia Krafft.
The western section of the Sete Cidades caldera is seen in this view from the southern caldera rim. Lagoa Verde (bottom right) and Lagoa Azul (center right) stretch across the center of the caldera, bounded to the east and west by pyroclastic cones. Here, three forested cones can be seen that formed during the past 5,000 years. These are the Caldeira Seca (left), Caldeira do Alferes (left center), and Seara (behind and to the right of Alferes). The broadly circular caldera forms the horizon in the background.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
The tree lined, approximately 500 x 700 m, Caldeira Seca pumice ring (center) on the floor of the Sete Cidades caldera, with Lagoa Azul and the northeast wall of the caldera in the background. The southeastern flank of the Calderia do Alferes is seen in the upper left. Caldeira Seca formed during a 15th-century phreatomagmatic eruption in which large amounts of pumice ash, lapilli and blocks were erupted.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
The SE floor of Sete Cidades caldera contains a large trachytic lava dome with two craters containing Lagoa de Santiago and Lagoa Rasa. The rim of Lagoa de Santiago crater is visible in the center. The visible lakes in this image are the Lagoa Verde (left foreground) and Lagoa Azul (left background), that occupy much of the caldera floor. Both explosive eruptions forming Santiago and Rasa occurred within the last 5,000 years.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
Caldeira do Alferes (center) is one of a group of pyroclastic cones constructed on the floor of Sete Cidades caldera. The adjacent cone of Seara is just visible in the background, right of Caldeira do Alferes in this view from the western caldera rim. The forested slope seen in the right foreground is Caldeira Seca. Explosive trachytic eruptions occurred at least 17 times in the past 5,000 years within the caldera.

Photo by Rick Wunderman, 1997 (Smithsonian Institution).
A small peninsula extends into Lagoa Azul ("Blue Lake"), one of two main lakes partially filling the floor of the summit caldera on Sete Cidades volcano at the western end of Sao Miguel Island. The 5-km-wide caldera was formed in three major eruptions at about 36,000, 29,000 and 16,000 years ago, and at least 17 eruptions have occurred here in the last 5,000 years. This view looks to the northwest from the rim of a post-caldera cone containing Lagoa Santiago. Two other post-caldera cones, Caldeira do Alferes and Seara, 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).
GVP Map Holdings

The Global Volcanism Program has no maps available for Sete Cidades.

Smithsonian Sample Collections Database

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

External Sites