🌋VolcanoAtlas

Furnas

The Boiling Heart of the Azores

Elevation

805 m

Last Eruption

1630

Type

Stratovolcano

Country

Portugal

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskLow
Infrastructure RiskModerate
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity396 years agoHistoricalHistorically active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Normal
No recent activity. Routine monitoring continues.
aerial photo of body of water

Nuno Antunes

via Unsplash

Other Volcanoes in Portugal

Interesting Facts

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The 1630 eruption of Furnas killed approximately 200 people — the deadliest volcanic event in Azorean history.

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Furnas has produced two VEI 5 eruptions (~80 CE and 1630 CE), the same explosive magnitude as Vesuvius's 79 AD eruption.

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The traditional cozido das Furnas stew is cooked by burying pots in geothermally heated ground for 6–7 hours.

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Approximately 1,500 people live in Furnas village, directly on the caldera floor surrounded by active fumaroles.

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Terra Nostra Park's iron-rich thermal pool maintains a natural temperature of 35–40°C year-round.

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At least 11 trachytic pumice layers deposited over 5,000 years testify to Furnas' persistent explosive activity.

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Diffuse CO₂ degassing from the caldera floor has caused livestock deaths in low-lying areas.

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The 395-year repose since 1630 is the longest in Furnas' post-80 CE record.

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Furnas' caldera walls rise ~500 m above the floor, creating a bowl that would trap pyroclastic flows.

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Azorean geothermal energy, concentrated at volcanoes like Furnas, supplies ~42% of São Miguel's electricity.

Frequently Asked Questions

Is Furnas an active volcano?
Yes, Furnas is classified as active by the Smithsonian Global Volcanism Program. Although it last erupted in 1630, its vigorous hydrothermal activity — boiling fumaroles, hot springs exceeding 100°C, diffuse CO₂ degassing — confirms an active magmatic system. CIVISA monitors continuously. With two VEI 5 eruptions and a 395-year repose exceeding average intervals, future activity is considered highly probable.
What is cozido das Furnas?
Cozido das Furnas is a traditional Azorean stew cooked using volcanic geothermal heat. Pots of meat, sausages, vegetables, and potatoes are lowered into holes in the geothermally heated ground beside Lagoa das Furnas, slow-cooking for 6–7 hours at over 100°C. It is the signature dish of the Azores and a major tourist draw.
Can you swim in the hot springs at Furnas?
Yes. Terra Nostra Park features an iron-rich thermal pool at 35–40°C surrounded by a botanical garden. Poça da Dona Beija offers pools at varying temperatures. Both charge admission. The lakeside caldeiras are too hot to bathe in.
How dangerous is Furnas?
Furnas poses significant hazard. Two VEI 5 eruptions demonstrate capacity for Plinian explosions, and ~5,000 people live within the caldera. A repeat of 1630 would generate pyroclastic flows, thick pumice falls, and lahars. Chronic CO₂ degassing is also a concern.
When did Furnas last erupt?
Furnas last erupted September 3, 1630, in a VEI 5 Plinian event that killed ~200 people — the deadliest eruption in Azorean history. The 395-year repose since is the longest gap in the post-80 CE record.
Is it safe to visit Furnas?
Furnas is safe to visit under current conditions. CIVISA monitors continuously and no signs of imminent eruption exist. Stay on marked paths near fumaroles. Tens of thousands visit annually without incident.