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Sete Cidades Massif

Sete Cidades

Stratovolcano · Portugal · 842m

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.
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: Photo by R.V. Fisher, 1980 (University of California Santa Barbara). · Wikimedia Commons
Type
Stratovolcano
Country
Portugal
Region
Atlantic Ocean Volcanic Regions / Azores-Terceira Rift Volcanic Province
Elevation
842m
Coordinates
37.865, -25.785
Last eruption
1880
Tectonic setting
Rift zone / Oceanic crust (< 15 km)
Landform
Composite
Major rock type
Trachyte / Trachydacite
Geological summary

Sete Cidades volcano at the western end of Sao Miguel Island contains a 5-km-wide summit caldera occupied by two caldera lakes. 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 on the caldera floor have been the source of a dozen trachytic pumice-fall deposits erupted during the past 5,000 years. Recorded eruptions date back to the 15th century and have occurred both within the caldera and from submarine vents off the west coast.

From Wikipedia

Sete Cidades Massif is a stratovolcanic complex, referring to a polygenetic volcano and caldera, located in western part of the island of São Miguel, in the Portuguese archipelago of the Azores. More recognizable for the Lagoa das Sete Cidades at its centre, the volcanic complex includes centuries of geomorphological structures that include lava domes, cones, lava flows and maar geomorphology that have marked its history.

Wikipedia · CC BY-SA · Read full article →

Eruption history

Summary (VEI over time)
Click a bar to see individual eruptions
3050 BCE~2853 BCE · 1 eruptions · max VEI 42064 BCE~1867 BCE · 1 eruptions · max VEI ?881 BCE~684 BCE · 1 eruptions · max VEI ?92 BCE~105 · 1 eruptions · max VEI 4302~500 · 1 eruptions · max VEI 4500~697 · 1 eruptions · max VEI 3894~1091 · 1 eruptions · max VEI 21091~1288 · 1 eruptions · max VEI 21288~1486 · 1 eruptions · max VEI 41486~1683 · 2 eruptions · max VEI 21683~1880 · 5 eruptions · max VEI 33050 BCE1867 BCE684 BCE5001683

Detailed timeline

  1. 1880VEI 0Geological estimate
    1880 – Ongoing
    Volcano Uncertain: submarine vent off Sao Miguel
  2. 1861VEI 0Geological estimate
    1861 – Ongoing
    Volcano Uncertain: submarine vent off Sao Miguel
  3. 1811VEI 2Observed
    1811-02-01 – 1811-02-08
    Submarine vent west of Sete Cidades
  4. 1811VEI 3Observed
    1811-06-14 – 1811-06-22
    Submarine vent west of Sete Cidades
  5. 1713VEI 2Observed
    1713 – Ongoing
    West flank (Pico das Camarinhas)
  6. 1682VEI 2Observed
    1682-12-13 – Ongoing
    Submarine vent west of Sete Cidades
  7. 1638VEI 2Observed
    1638-07-03 – 1638-07-28
    Submarine vent west of Sete Cidades
  8. 1444VEI 4Observed
    1444 – Ongoing
    SW side of caldera (Caldeira Seca)
  9. 1110 (±50 yrs)VEI 2Geological estimate
    1110 – Ongoing
    West flank (Ponta de Ferraria)
  10. 950 (±100 yrs)VEI 2Geological estimate
    950 – Ongoing
    SE flank (Ferraria)
  11. 670 (±150 yrs)VEI 3Geological estimate
    670 – Ongoing
    SE flank (Carvao)
  12. 380 (±300 yrs)VEI 4Geological estimate
    380 – Ongoing
    SE caldera floor (Lagoa Rasa)
  13. 90 (±100 yrs)VEI 4Geological estimate
    90 – Ongoing
    SE caldera floor (Lagoa de Santiago)
  14. 750 BCE (±300 yrs)VEI ?Geological estimate
    BCE 750 – Ongoing
    SE flank (Eguas)
  15. 2050 BCE (±1000 yrs)VEI ?Geological estimate
    BCE 2050 – Ongoing
    Caldeira do Alfreres and NW flank
  16. 3050 BCEVEI 4Geological estimate
    BCE 3050 – Ongoing
    Seara Cerrado da Ladeira

External links

⚠ For reference only. Not for emergency response.