Age: 2,800 years
Height: 660 ft (200 m)
Width: 1 mile (1.6 km)
Hverfjall, also known as Hverfell, is a striking tuff ring volcano located in northern Iceland, near the eastern shore of Lake Mývatn. This impressive geological feature is renowned for its near-perfect circular shape and dramatic black ash slopes, making it one of the most visually captivating craters in the world. Formed from a powerful explosive eruption around 2,500 to 2,800 years ago, it exemplifies Iceland's dynamic volcanic landscape and attracts hikers, geologists, and nature enthusiasts alike.
Hverfjall's origins trace back to a phreatomagmatic eruption
approximately 2,500 years before present (BP), occurring in the southern
section of the Krafla fissure swarm—a volcanically active rift zone in
Iceland. This type of eruption happens when rising magma interacts
explosively with groundwater or surface water, leading to the rapid
fragmentation of rock and the ejection of tephra (volcanic ash and
fragments). The event was particularly violent, building up the crater's
walls from layers of compacted ash and lapilli in a relatively short
time, possibly just a few days. Unlike typical stratovolcanoes,
Hverfjall is a tephra cone or tuff ring, characterized by its broad,
shallow crater formed solely from explosive debris rather than lava
flows.
The eruption's intensity scattered ash over a wide area,
contributing to the region's unique geology. Some sources date the
formation more precisely to around 2,800 years ago, highlighting the
interaction between basaltic magma and the wet environment near Lake
Mývatn as the key trigger. Today, the crater remains dormant, but its
location in the active Krafla system means the surrounding area
experiences ongoing geothermal activity, including fumaroles and hot
springs nearby.
The crater's most notable feature is its immense size and symmetry.
It measures about 1 kilometer (0.62 miles) in diameter, with the rim
rising to an elevation of approximately 452 meters (1,483 feet) above
sea level—roughly 200 meters (656 feet) above the surrounding terrain.
The interior bowl plunges to a depth of around 140 to 240 meters (459 to
787 feet), creating a bowl that's nearly as deep as the crater walls are
high, which is an unusual trait among similar formations. The slopes are
composed of dark, fine-grained tephra, giving the structure a stark,
almost lunar appearance with subtle ridges formed by erosion over
millennia.
From aerial views, Hverfjall appears as a massive,
bowl-shaped depression with steep inner walls and gentler outer slopes,
often dusted with patches of green vegetation at its base during summer.
The crater floor is flat and barren, occasionally hosting small ponds
after heavy rain, but it lacks any central vent or lava features typical
of other volcanoes.
Nestled in the Mývatn region, Hverfjall is part of a larger volcanic and geothermal wonderland that includes lava fields, pseudocraters, and the nearby Dimmuborgir rock formations. The area is rich in biodiversity, with Lake Mývatn supporting a thriving ecosystem of birds, insects, and aquatic life, despite the harsh volcanic soil. Vegetation around the crater is sparse, consisting mainly of hardy mosses, lichens, and grasses that have colonized the ash over time, adding subtle color contrasts to the black landscape. The proximity to geothermal sites like Hverir (with its boiling mud pots) enhances the sense of an otherworldly environment.
Accessing Hverfjall is straightforward, with a parking area at the
base connected by a short gravel road off Route 848. The primary
activity is hiking to the rim: a steep but well-maintained trail ascends
about 150-200 meters in elevation over roughly 1 kilometer, taking 20-45
minutes depending on fitness level. Once at the top, visitors can walk
the full 3.2-kilometer (2-mile) circumference of the rim path, offering
panoramic views of Lake Mývatn, distant mountains, and the volcanic
plains below. The trail is gravelly and exposed, so sturdy shoes,
weather-appropriate clothing, and caution in windy conditions are
recommended; descending into the crater is prohibited to prevent
erosion.
The site is free to visit year-round, though summer
(June-August) provides the best weather and midnight sun for extended
hikes. In winter, snow can make trails slippery, and access roads may
close. Nearby attractions like the Mývatn Nature Baths make it an ideal
stop on the Diamond Circle route.
Hverfjall holds cultural importance in Icelandic folklore and serves as a key site for studying phreatomagmatic volcanism, offering insights into similar formations worldwide. It's protected as part of the Mývatn-Laxá Conservation Area, emphasizing its role in preserving Iceland's natural heritage. For scientists, the crater's well-preserved layers provide a natural record of ancient eruptions, aiding research on volcanic hazards in rift zones.