Fjallsárlón receives a tenth of the visitors that crowd Jökulsárlón, six kilometres to the east, yet its glacier tongue advances while its famous neighbour recedes. The lagoon formed in the 1970s as Fjallsjökull — a southern outlet of Vatnajökull, Europe's largest ice cap — began its retreat from the valley floor.
Unlike Jökulsárlón's broad, placid basin, Fjallsárlón remains narrow and steep-sided, its water a deeper turquoise fed by meltwater that has filtered through centuries-compacted ice. The glacier's lower reaches retain the blue ice formations and crevasse fields that make fjallsarlon glacier walk tours a cornerstone of Iceland's adventure tourism.
Vatnajökull covers eight percent of Iceland's landmass, its ice reaching depths of 950 metres in places. Fjallsjökull's terminus sits at the southern edge of this expanse, where volcanic bedrock forces the ice into sharp ridges and pressure waves. The glacier's surface records its history in layers: black tephra bands from the 1362 Öræfajökull eruption, ash seams from Grímsvötn's 2011 event, and the pale blue of compressed ice that has survived multiple melt-freeze cycles. Guided glacier treks depart from the lagoon's eastern shore, where crampons and ice axes are distributed before the climb onto the glacier's lower tongue.
The lagoon itself functions as a dynamic iceberg nursery. Calving events occur several times daily during summer months, sending house-sized blocks into water that rarely exceeds four degrees Celsius. Zodiac tours navigate between these icebergs, approaching the glacier face where seracs — vertical ice columns — lean precariously before collapsing. The lagoon's depth, reaching 200 metres in places, allows icebergs to drift in slow rotation, their submerged portions nine times the volume of what shows above the waterline. Seals haul out on the larger bergs, particularly in late summer when young pups practise diving in the protected waters.
Fjallsárlón's position within Vatnajökull National Park places it at the intersection of glacial geology and volcanic activity. The bedrock beneath the ice includes remnants of the Öræfajökull stratovolcano, Iceland's highest peak at 2,110 metres. When subglacial eruptions occur — the last in 1727 — meltwater surges through the ice, carving new drainage channels and altering the lagoon's morphology within hours. The glacier walk routes change seasonally as guides assess crevasse stability and ice thickness, ensuring that visitors traverse only the sections where the ice exceeds three metres in depth and surface melt has not compromised structural integrity.
15 hr
