Last eruption
~1341 AD
Dormant but geothermally active.
Brennisteinsfjöll Volcanic System, Reykjanes Peninsula
A volcanic system on the Reykjanes Peninsula with active fumaroles and solfataras, just 20 km from Reykjavik, part of the peninsula's geothermally active volcanic belt.
Region
Reykjanes Peninsula
Near Reykjavik. Year-round access.
Brennisteinsfjöll ("Brimstone Mountains") is one of the volcanic systems lining the Reykjanes Peninsula, Iceland's most accessible volcanic region. Though its last eruption was around 1341, the area remains geothermally active with steaming fumaroles and sulfur-depositing solfataras. Its proximity to Reykjavik makes it an easy day trip for those interested in volcanic geology.
Sources and page update
Updated: 2026-09-10
This page is for trip planning, not emergency guidance. Stay on marked paths near geothermal features. Ground can be hot and unstable.
For sourcing standards and how to report an error, see the editorial policy.
Official sources to check
Features
Fumaroles & solfataras
Active steam vents and sulfur deposits.
Distance
~20 km from Reykjavik
One of the closest volcanic systems to the capital.
What to Expect
- Volcanic system classification: fissure swarm with multiple eruptive vents along the Reykjanes oblique rift
- Last eruption ~1341 AD: small basaltic lava flows; dormant for ~685 years but geothermally active
- Part of the Reykjanes volcanic belt now in a new eruptive cycle; Fagradalsfjall eruptions began in 2021 nearby
- Active fumaroles and solfataras with bright yellow sulfur deposits and strong sulfurous gas emissions
- Moss-covered medieval lava fields from historical eruptions visible along hiking trails
- Identify the exact walking route east of Kleifarvatn before travelling
- Visitors can observe the contrast between ancient lava flows and active geothermal venting
Nearby Attractions
- Blue Lagoon geothermal spa
- Kleifarvatn lake
- Krýsuvík geothermal area
- Fagradalsfjall recent eruption sites
- Reykjanes Geopark (UNESCO)
- Seltún hot springs and mud pools
How to Get There
- Choose the exact trail or volcanic feature, not only the broad system name
- Check the approach road, walking route and current weather together
- Kleifarvatn and Seltún are separate destinations; do not use their parking areas as an assumed route into Brennisteinsfjöll
Best Time to Visit
- Walking conditions depend on snow, visibility, wind and the precise route
- Use current road and land-manager information before setting out
- Historical eruption dates do not establish a present-day access status
A volcanic system, not a roadside summit
The Smithsonian profile places Brennisteinsfjöll east of Kleifarvatn and describes northeast–southwest crater rows and small shield volcanoes. Its catalogue lists the latest confirmed episode around 1341, with a one-year dating uncertainty.
The system name covers several features. A stop at Kleifarvatn or Seltún does not mean you have reached a Brennisteinsfjöll trailhead. Choose an exact walking objective and obtain a route map and current access advice before setting out.
Planning help
Brennisteinsfjöll FAQs
Quick answers with safety notes where it matters.
When did Brennisteinsfjöll last erupt?
Brennisteinsfjöll last erupted around 1341 AD, producing small lava flows. The volcanic system has been quiet since, but the Reykjanes Peninsula's recent volcanic reawakening has heightened interest in all volcanic systems in the area.
What are the fumaroles at Brennisteinsfjöll?
Fumaroles are vents where volcanic gases and steam escape from the ground. At Brennisteinsfjöll, active fumaroles and solfataras (sulfur-depositing vents) indicate ongoing geothermal activity beneath the surface, producing a distinctive sulfur smell.
Can you hike at Brennisteinsfjöll?
Yes, there are hiking trails in the Brennisteinsfjöll area, requiring a route chosen for the exact feature you want to visit. The terrain includes old lava fields, moss-covered rock, and geothermal areas. Stay on marked paths near thermal features.
How far is Brennisteinsfjöll from Reykjavik?
Brennisteinsfjöll is approximately 20 km southeast of Reykjavik, one of the closest volcanic systems to the capital. Distance from the capital does not establish access to a particular trail.
Is Brennisteinsfjöll connected to the Reykjanes eruptions?
Brennisteinsfjöll is one of several volcanic systems on the Reykjanes Peninsula. While the recent eruptions have been at Fagradalsfjall and nearby fissures, scientists monitor all Reykjanes systems as the peninsula enters a new volcanic period.
For a countrywide view of Iceland’s volcanic systems, explore our Iceland statistics.