Grímsvötn
Iceland's Most Frequently Erupting Volcano
Elevation
1,719 m
Last Eruption
2011
Type
Caldera
Country
Iceland
Location
Loading map...
Volcanic Hazards & Risk Assessment
Primary Hazards
- Pyroclastic flows and surges
- Large explosive eruptions (VEI 4+)
- Ash fall and tephra deposits
- Lahars and debris flows
Risk Level
Population at RiskHigh
Infrastructure RiskHigh
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
| Metric | Value | Global Ranking | Significance |
|---|---|---|---|
| Total Recorded Eruptions | Unknown | Low | Moderately active volcano |
| Maximum VEI | VEI Unknown | Minor | Local impact potential |
| Recent Activity | 15 years ago | Recent | Recently active |
Monitoring & Alert Status
Monitoring Networks
Global Volcanism Program
International eruption database
Current Status
Watch
Dormant but monitored. Capable of renewed activity.
Authority Sources
Other Volcanoes in Iceland
- Bárðarbunga
Stratovolcano (subglacial)
- Eyjafjallajökull
Stratovolcano
- Hekla
Stratovolcano
- Katla
Subglacial volcano (fissure vents)
Interesting Facts
🌋
The 1783 Laki fissure eruption — part of the Grímsvötn volcanic system — produced approximately 15 km³ of basaltic lava, the largest historical lava flow on Earth.
🌋
Grímsvötn's 85 recorded eruptions make it Iceland's most frequently erupting volcano, with an average recurrence interval of roughly 7 years since 1900.
🌋
The volcano's subglacial caldera lake sits beneath approximately 200 m of glacial ice, and intense geothermal heat melts roughly 0.5 km³ of ice per year.
🌋
The 1996 jökulhlaup from Grímsvötn reached a peak discharge of 45,000 m³/s — comparable to the average flow of the Amazon River — and destroyed Iceland's longest bridge.
🌋
Sulfuric emissions from the 1783 Laki eruption caused an estimated 23,000 excess deaths in England alone and contributed to crop failures across Europe.
🌋
The 2011 eruption produced approximately 0.7 km³ of tephra — roughly ten times the volume ejected by the more disruptive 2010 Eyjafjallajökull eruption.
🌋
Benjamin Franklin is credited as one of the first people to link the 1783 'dry fog' over Europe to volcanic activity, writing his observations from Paris.
🌋
Grímsvötn's earliest known eruption, around 8230 BCE, rated VEI 6 — the same scale as the 1883 Krakatoa and 1991 Pinatubo eruptions.
🌋
The Reverend Jón Steingrímsson's eyewitness account of the 1783 Laki eruption is considered one of the most detailed and scientifically valuable volcanic observations in history.
🌋
Grímsvötn lies within Vatnajökull National Park, which at approximately 14,000 km² is the largest national park in Europe.
🌋
The Laki eruption's atmospheric effects weakened the African and Indian monsoons, contributing to famine as far away as Egypt and Japan.
🌋
Only the southern caldera rim — the nunatak of Grímsfjall at 1,719 m — is visible above the ice surface; the rest of the 6 × 8 km caldera is completely buried.
Frequently Asked Questions
Is Grímsvötn still active?
Grímsvötn is one of the most active volcanoes on Earth and is classified as active by the Icelandic Meteorological Office. It last erupted in May 2011 in a VEI 4 event that sent an ash plume to 20 km altitude. Since then, the volcano has shown continuous geothermal activity, progressive seismic unrest, and measurable caldera inflation detected by GPS instruments. Volcanologists consider Grímsvötn to be in a late recharge phase, and its current repose period of over 13 years already exceeds the modern average interval of approximately 7 years between eruptions. Continuous monitoring detects precursory signals including seismicity, deformation, and gas emissions, providing advance warning of future eruptions.
When did Grímsvötn last erupt?
Grímsvötn's most recent eruption began on May 21, 2011, and lasted approximately one week until May 28. The eruption was rated VEI 4 and produced an ash plume reaching approximately 20 km (66,000 ft) into the stratosphere — the largest eruption in Iceland since Katla's 1918 event. The eruption generated about 0.7 km³ of tephra, caused the closure of Keflavík International Airport for 24 hours, and resulted in hundreds of cancelled flights across northern Europe. Despite its large size, the 2011 eruption caused far less aviation disruption than the smaller 2010 Eyjafjallajökull eruption because Grímsvötn's basaltic ash particles are coarser and settle from the atmosphere more rapidly.
What is a jökulhlaup?
A jökulhlaup (pronounced 'YUR-kul-hloip') is a glacial outburst flood caused by the sudden drainage of water stored beneath or within a glacier. At Grímsvötn, intense geothermal heat continuously melts the base of the overlying Vatnajökull icecap, filling a subglacial lake within the caldera. When the water level rises high enough to lift the ice dam — typically every 5–10 years — the lake drains catastrophically through subglacial channels, producing enormous floods across the Skeiðarársandur outwash plain to the south. The 1996 jökulhlaup reached a peak discharge of 45,000 m³/s, carrying house-sized ice blocks and destroying the Skeiðará bridge on Iceland's Route 1 ring road.
How does Grímsvötn compare to Eyjafjallajökull?
Grímsvötn is far more active and powerful than Eyjafjallajökull. Grímsvötn has 85 recorded eruptions compared to Eyjafjallajökull's 6, and its maximum VEI of 6 dwarfs Eyjafjallajökull's maximum of VEI 4. The 2011 Grímsvötn eruption produced roughly ten times more tephra than the 2010 Eyjafjallajökull event. However, Eyjafjallajökull gained greater international fame because its fine-grained silicic ash lingered in the atmosphere for weeks, shutting down European airspace for six days and stranding approximately 10 million passengers. Grímsvötn's basaltic ash is coarser and settles faster, so despite producing larger eruptions, it tends to cause shorter-duration aviation disruption.
What was the Laki eruption?
The Laki eruption (1783–1784) was a catastrophic fissure eruption that occurred along the Skaftár Fires (Lakagígar) fissure, part of the Grímsvötn volcanic system, 25 km southwest of the Grímsvötn caldera. Over eight months, a 27-km-long fissure produced approximately 15 km³ of basaltic lava — the largest historical lava flow on Earth — and released 122 million tonnes of sulfur dioxide. The eruption killed roughly one-fifth of Iceland's population through famine and fluorine poisoning, caused an estimated 23,000 excess deaths in England, and lowered Northern Hemisphere temperatures by 1–3°C. It remains one of the deadliest and most climatically significant eruptions in recorded history.
Could Grímsvötn erupt again soon?
Volcanologists consider a near-term eruption of Grímsvötn to be likely. The volcano's average recurrence interval since 1900 is approximately 7 years, and the current repose period since the 2011 eruption has already exceeded 13 years as of early 2025. GPS monitoring has detected progressive caldera inflation indicating magma accumulation, seismic activity has increased since approximately 2017, and geothermal heat output remains elevated. While the precise timing of the next eruption cannot be predicted, the Icelandic Meteorological Office maintains continuous surveillance and has demonstrated the ability to detect precursory signals days to weeks before eruptions begin.
How tall is Grímsvötn?
Grímsvötn's summit elevation is officially 1,719 m (5,640 ft) above sea level, measured at the exposed southern caldera rim called Grímsfjall. However, this figure is somewhat misleading because the vast majority of the volcano is buried beneath the Vatnajökull icecap. The caldera floor sits considerably lower, and the subglacial caldera lake lies at approximately 1,400 m elevation. The caldera itself measures 6 × 8 km across, making it one of Iceland's largest calderas. By comparison, neighboring Bárðarbunga's summit reaches 2,009 m, and Öræfajökull — Iceland's tallest volcano — stands at 2,110 m, both also beneath Vatnajökull.
Can you visit Grímsvötn?
Grímsvötn is not accessible for casual tourism because it lies almost entirely beneath the Vatnajökull icecap, far from any road or trail. Reaching the caldera requires specialized glacier travel equipment and is restricted to scientific expeditions and extreme-adventure groups. However, visitors can explore the Grímsvötn volcanic system's dramatic features from more accessible locations: the Laki crater row (accessible via highland road F206 in summer), the Skeiðarársandur outwash plain (visible from Route 1), and the Skaftafell area of Vatnajökull National Park, which offers glacier hiking with views toward the icecap interior. The town of Kirkjubæjarklaustur, 70 km southwest, is the nearest base for exploration.
What type of volcano is Grímsvötn?
Grímsvötn is classified as a caldera volcano, meaning its central feature is a large collapse depression formed by repeated eruptions emptying the underlying magma chamber. The caldera measures 6 × 8 km and was shaped by multiple collapse events over thousands of years. Grímsvötn produces predominantly basaltic to picro-basaltic magma, typical of Iceland's rift zone volcanism. Its eruption style is primarily phreatomagmatic — highly explosive interactions between hot magma and glacial ice or meltwater — which generates prolific ash columns despite the typically low-viscosity basaltic composition. The broader Grímsvötn volcanic system also includes extensive NE–SW trending fissure swarms, including the 27-km Laki fissure that produced massive effusive eruptions.
Why does Grímsvötn erupt so often?
Grímsvötn's extraordinary eruption frequency stems from its position at the intersection of two powerful magmatic sources. It sits directly above the Iceland mantle plume — a column of abnormally hot rock rising from deep in Earth's mantle — and along the Mid-Atlantic Ridge, where the North American and Eurasian tectonic plates are pulling apart at approximately 2 cm per year. This combination delivers a sustained, high-volume supply of basaltic magma to shallow depths beneath the volcano. Additionally, the overlying Vatnajökull icecap plays a role: the weight of the ice acts as a pressure cap, and interactions between magma and glacial meltwater can trigger eruptions that might not occur under ice-free conditions.