Mýrdalsjökull and Katla: A Glacier with Secrets

Beneath the pristine white expanse of Mýrdalsjökull glacier lies one of Iceland's most volatile and feared volcanoes: Katla. This glacier-volcano system in southern Iceland represents one of nature's most intriguing partnerships—ice and fire locked in an eternal dance that has shaped both landscape and legend for centuries.

The Ice Cap Above

Mýrdalsjökull, Iceland's fourth-largest glacier, sprawls across 596 square kilometres of the Icelandic highlands, its ice reaching depths of up to 250 metres. The glacier sits at elevations ranging from 1,380 metres at its highest point down to sea level, creating a dramatic ice cap that dominates the horizon south of the Ring Road.

Unlike the more accessible Vatnajökull to the east, Mýrdalsjökull maintains an air of mystery and menace. Local folklore has long regarded it with suspicion—and for good reason. The glacier's name, meaning "marsh-dale glacier," belies the explosive potential that simmers beneath its frozen surface.

The ice cap feeds numerous outlet glaciers, including Sólheimajökull, which provides the most accessible window into this frozen world. From the car park at the end of Route 221, a 1.2-kilometre walk across black volcanic sand leads to the glacier's terminus, where visitors can witness the dramatic interplay between ice and the dark volcanic substrate below.

Katla: The Sleeping Giant

Beneath Mýrdalsjökull's ice lies Katla, a volcanic system with a caldera measuring 10 kilometres in diameter—one of the largest in Iceland. This subglacial volcano has earned its fearsome reputation through centuries of explosive eruptions, with historical records documenting major eruptions in 1625, 1660, 1721, 1755, 1823, 1860, and most recently in 1918.

Katla's eruptions follow a pattern that has kept volcanologists on edge: major eruptions typically occur every 40 to 80 years. With the last significant eruption occurring in 1918—over a century ago—the volcano is considered overdue by geological standards. This lengthy quiet period has only intensified scientific monitoring and public fascination with the sleeping giant.

The 1918 eruption demonstrated Katla's destructive potential. The explosion melted vast quantities of glacial ice, creating a massive jökulhlaup (glacial outburst flood) that swept across the Mýrdalssandur plain. The floodwaters carried icebergs weighing several tonnes and deposited so much sediment that Iceland's coastline extended by up to 5 kilometres in some areas.

The Science of Ice and Fire

The relationship between Mýrdalsjökull's ice and Katla's volcanic activity creates a unique and dangerous dynamic. The glacier's immense weight—estimated at approximately 20 billion tonnes of ice—acts as a pressure lid on the volcanic system below. This pressure affects how and when eruptions occur, often making them more explosive when they finally break through.

Geothermal activity beneath the glacier creates a complex system of ice caves, some accessible to experienced guides and visitors. These caves form when volcanic heat melts the ice from below, creating ethereal blue chambers that shift and change with the seasons. However, the unstable nature of these formations means access is strictly controlled and weather-dependent.

Recent scientific monitoring has detected increasing seismic activity and ground deformation around Katla, suggesting the volcanic system remains very much alive. The Icelandic Met Office maintains constant surveillance through a network of seismometers and GPS stations, providing early warning systems for any significant changes.

Exploring the Glacier's Edge

For visitors seeking to experience Mýrdalsjökull, several options provide safe access to this formidable landscape. Glacier hiking tours on Sólheimajökull operate year-round, with prices ranging from 9,900 ISK (€70) for basic glacier walks to 28,900 ISK (€205) for comprehensive ice climbing experiences.

The optimal visiting period extends from May through September, when daylight hours are longest and weather conditions most stable. Winter visits are possible but require greater preparation and flexibility due to Iceland's unpredictable weather patterns.

Professional glacier tours include necessary safety equipment: crampons, helmets, harnesses, and ice axes. The contrast between the glacier's pristine ice and the black volcanic ash embedded within creates otherworldly scenery that changes dramatically depending on recent volcanic activity elsewhere in Iceland.

Practical Considerations

Reaching Mýrdalsjökull requires careful planning. The glacier's main access points lie along Route 1 between Hvolsvöllur and Vík. The turn-off for Sólheimajökull (Route 221) is clearly marked and leads 4.5 kilometres to the glacier car park.

Independent exploration of the glacier is strongly discouraged without proper equipment and experience. Crevasses, unstable ice formations, and the constant threat of jökulhlaups make professional guidance essential. Several Reykjavík-based tour operators offer day trips combining glacier exploration with visits to nearby attractions like Seljalandsfoss and Skógafoss waterfalls.

Living with Uncertainty

The communities surrounding Mýrdalsjökull have learned to live with the constant presence of Katla. Vík, Iceland's southernmost village with 291 residents, maintains detailed evacuation plans and regular emergency drills. The village's elevated position and designated safe zones reflect centuries of local knowledge about Katla's behaviour.

This coexistence between human settlement and geological forces exemplifies Iceland's relationship with its dynamic landscape. Mýrdalsjökull and Katla represent both the beauty and danger inherent in volcanic islands, where fire and ice create landscapes of extraordinary power and haunting beauty.

The glacier continues to retreat in response to climate change, potentially affecting the delicate balance that has kept Katla dormant. As the ice thins, scientists debate whether reduced glacial pressure might influence future volcanic activity—adding another layer of complexity to an already fascinating geological system.

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