Iceland’s highest mountain, Öræfajökull at 2110 meters, and its deepest lake, Jökulsárlón reaching 284 meters, sit side by side on the island’s southeastern margin. Their striking proximity reflects more than coincidence: it reveals the intersection of several major geological boundaries that meet precisely at this location. The key to understanding this lies in two geographic lines—64°N and 16°40’30”W—which together frame a tectonic corner of Iceland.
The 64th parallel is an important structural boundary across Iceland. North of this line, the East Volcanic Zone is divergent, but south of 64°N the South Iceland Volcanic Belt is not. The South Iceland Seismic Zone is also found on on 64°N. This shift happens along the 64°N line, and Öræfajökull lies exactly upon this transition.
The meridian of 16°40’30”W forms another significant axis. This longitude aligns with the central line of the North Volcanic Zone farther north. When extended southward, this same line passes directly through Öræfajökull. In other words, the volcano sits on a southern continuation of one of Iceland’s major volcanic and tectonic axes, even though it lies east of the island’s main rift zones and firmly on the Eurasian Plate. Its position makes it a tectonic outlier—disconnected from the active rifts.
The relationship between Öræfajökull and the volcanic systems to the north further reveals the underlying structure. At the northern edge of Vatnajökull, the volcano Kverkfjöll stands at the southern end of the North Volcanic Zone, positioned at what can be seen as the northern corner of a polygon, as seen on the map. Öræfajökull sits directly south of Kverkfjöll along the same north–south axis, forming the southern corner of that same convection polygon.
At the 16°40’30”W line, the drift vectors diverge in different directions, and near 64°N, the vectors also change directions, from NE to NW. Where these shifting vectors meet, the crust experiences a twisting or hinging effect. Öræfajökull is located precisely at this corner where drift vectors split and rotate relative to each other.
This combination of structural transitions produces the unusual pairing of Iceland’s highest and lowest points. At Öræfajökull, all the division lines between convecton rolls are concentrated at one spot, and by the resistance of crustal blocks caught at the hinge of changing stress fields. Just a short distance away, the basin that now holds Jökulsárlón lies in a zone of subtle tectonic sag created by that same hinge. As the Breiðamerkurjökull glacier retreated, it carved this weakened zone even deeper, creating a basin that today reaches far below sea level. Thus, uplift and subsidence—opposing expressions of the same tectonic corner—appear literally side by side.
Öræfajökull, one of Iceland’s most powerful stratovolcanoes, and Jökulsárlón, carved into a structurally lowered basin at the foot of a retreating glacier, together mark a location where Iceland’s tectonics, mantle flow, and glacial history intersect. Their juxtaposition encapsulates the geological complexity of southeast Iceland: a place where the island’s major structural lines cross, where mantle convection shifts direction, and where the twisting of drift vectors produces both the highest land and the deepest lake in a single, dramatic landscape.
Magic Magma 