Námafjall sulphur mountain in north Iceland

Several names are used for this area, sometimes as if they were interchangeable.

Námafjall is the mountain ridge. Its highest point reaches approximately 485 metres. Hverir, also known as Hverarönd, is the geothermal field immediately east of the mountain. This is the area of fumaroles, boiling mud pools and brightly altered ground beside Route 1. Námaskarð is the pass at the northern end of Námafjall through which the road crosses.

In ordinary use, Námafjall, Hverir and Námaskarð are often used for the same visitor destination. Geographically, however, they describe different parts of one landscape.

The distinction matters because the field does not exist in isolation. Hverir is the surface expression of heat and gases moving through fractured ground beneath Námafjall. The area belongs to the Krafla volcanic system, which extends northwards and includes some of Iceland’s most active volcanic and geothermal landscapes.

Krafla is frequently described through eruptions, fissures and lava fields. At Hverir, the same wider volcanic system expresses itself through chemical alteration.

A High-Temperature Geothermal System

Rain and groundwater descend through cracks and porous volcanic rock. At depth, the water encounters rock heated by the active volcanic system. It becomes extremely hot and rises again through fractures, carrying steam and dissolved gases towards the surface.

Pressure decreases as the water rises. Some of it boils before reaching the open air, producing the steam that escapes through fumaroles.

The sound can be as striking as the sight. Some vents release a continuous rush. Others hiss, pulse or roar as steam is forced through narrow openings. Wind changes the direction of the vapour and can suddenly carry an entire plume across the route.

The mud pools form through a related process. Geothermal fluids and acidic gases alter volcanic material, breaking minerals down and turning hard rock into clay. Gas rises through this wet clay, forming bubbles that swell and collapse at the surface.

The mud does not always behave in the same way. After wet weather, pools may appear more fluid. During drier periods, the mud can thicken and produce slower, heavier bubbles. Individual pools and vents also change as underground channels become blocked or new routes open.

Hverir is therefore not a fixed collection of permanent features. It is a changing surface above an active geothermal system.

Rock Transformed into Colour

The colours at Hverir are products of chemistry rather than decoration laid across otherwise ordinary ground.

Sulphur compounds contribute yellow tones. Oxidised iron produces reds and browns. Pale clay, dark mud and altered volcanic material create white, grey and almost black areas between them.

These colours change constantly with light and weather. Rain saturates the surface and strengthens the separation between red, yellow and grey ground. Dry conditions produce a paler and dustier landscape. Low sunlight reveals small ridges and erosion patterns, while flat light can reduce apparently intense colours to muted earth tones.

Steam changes them again. A plume can obscure the mountain and soften the entire field. Moments later, the wind may clear it and reveal every detail of the altered ground.

The characteristic smell comes primarily from hydrogen sulphide. It can be intense when wind carries steam directly across the route. Smell alone does not indicate a dangerous concentration; people can detect hydrogen sulphide at very low levels. Ordinary outdoor exposure at Hverir is part of the geothermal experience, but it can be uncomfortable for people with asthma or respiratory sensitivity. Anyone experiencing irritation, coughing, dizziness or nausea should move away from the plume rather than remain directly downwind.

Constructed Steam Vents

Some conspicuous features at Hverir resemble low stone cones from which steam escapes. They should not be mistaken for small natural volcanoes.

These are constructed features built around geothermal openings. They concentrate escaping steam through defined vents and have formed part of Hverir’s appearance for decades. Their exact shapes are human interventions, but the heat, pressure and vapour come from below.

They also show how easily geothermal activity can mislead. A dramatic steam column may appear to rise from a permanent, stable feature while the underlying system continues to change. Natural openings can weaken or become blocked, and new ones may form nearby. Ground is never made safe simply because visible steam has been channelled through a constructed vent.

Sulphur Before Tourism

The sulphur at Námafjall connected this remote geothermal area to trade far beyond Iceland.

Icelandic sulphur exports are recorded from at least the 13th century. Sulphur was valuable because it was an essential ingredient in gunpowder, alongside charcoal and saltpetre. As European demand for gunpowder increased, Icelandic deposits acquired political and commercial importance.

Sulphur was extracted at several geothermal locations around Mývatn, including ground east of Námafjall, on the mountain and north of it.

The work was difficult. Sulphur had to be collected or dug from geothermal ground, processed and transported across a country with few roads. From the Mývatn region, the material had to be carried north to the coast before export.

The trade became particularly important during the 16th century. Control over Icelandic sulphur attracted merchants and the Danish Crown, which sought to regulate and profit from production.

Mining here did not create deep shafts and extensive underground workings of the kind associated with metal mines elsewhere in Europe. The resource lay within altered geothermal ground. Extraction disturbed and reworked surface deposits, leaving traces far less durable than tunnels, stone buildings or large waste heaps.

Visitors should therefore not expect to find an obvious historic mine within Hverir. Almost no clearly recognisable remains survive. The name Námafjall preserves the history more visibly than the physical workings themselves.

Attempts to Revive the Industry

Efforts to increase sulphur production continued after the most important period of the trade had passed.

During the second half of the 18th century, sulphur was included in the Innréttingar programme, an attempt to develop organised industry in Iceland. This brought renewed interest in extraction and in methods of refining the raw material, but the results were limited.

By 1805, farmers throughout Skútustaðahreppur reportedly held rights to mine sulphur and sell it to the Danish king. They considered those rights of little value. Deposits had become depleted, and the long transport to Húsavík made the remaining sulphur difficult to exploit profitably.

Jónas Hallgrímsson, one of Iceland’s most important poets and natural scientists, examined the sulphur mines and processing methods in 1839. His involvement belongs to his scientific work and reflects the continuing hope that Iceland’s natural resources could support practical industry.

Most traditional sulphur extraction ended during the 19th century. The story nevertheless received one final industrial chapter at nearby Bjarnarflag.

A sulphur-processing factory was built there in 1938. It burned in 1939 and was subsequently rebuilt, but the renewed attempt was short-lived. Although outside the present Hverir walking area, it belongs to the same history. It was a modern effort to obtain commercial value from the geothermal resources that had given Námafjall its name centuries earlier.

Sulphur mining around the mountain never became a permanent large-scale industry. Its importance lies in connecting geothermal ground in northern Iceland to European commerce, warfare and state control. It was also among the closest Iceland came to mineral-based heavy industry before the 20th century.

Visiting Hverir Safely

Hverir lies immediately beside Route 1 and can be reached without a long walk. Its accessibility can create a false sense of security.

This is active geothermal ground. Marked routes are not merely intended to prevent erosion or organise the visit. They keep people away from surfaces that may conceal boiling water, hot mud, steam openings and softened ground.

A pale, dry-looking crust may be thin and unstable. No one should step beyond the established route to test the ground, approach a vent or obtain an unobstructed photograph. Water and mud must never be touched, regardless of whether a pool appears to be boiling vigorously.

Children require close supervision.

The ground-level route through the principal field is suitable for most ordinary visitors, although the surface is natural, uneven and sometimes muddy. Footwear should suit the conditions. Geothermal clay and mineral-rich water may stain shoes and clothing.

Steam direction can change without warning. A route that is clear when entered may be crossed by a dense plume moments later. Visibility normally returns quickly, but visitors should move carefully rather than rush through steam they cannot see beyond.

The main geothermal field can be understood from its marked routes. There is no need to leave them to experience its sound, smell, colour and activity.

The Námafjall Ridge and a Landscape Changed by Weather

A route leads onto the Námafjall ridge and provides a wider view over Hverir and the surrounding volcanic landscape. This is not simply an elevated continuation of the easy ground-level visit.

The route is steep and loose. It requires more care, stronger footwear and conditions suitable for an exposed climb. The descent can be particularly uncomfortable for visitors unused to unstable volcanic material, and wind can be much stronger on the ridge than in the field below.

The walk should not be presented as a routine activity for every visitor stopping at Hverir. It is a separate undertaking that must be judged according to weather, ability and route conditions.

There is no single season or type of weather in which Hverir becomes its definitive self. Every change produces a different field.

Rain darkens the clay, strengthens its colours and changes the consistency of the mud. Dry weather makes the ground lighter and dustier. Cold air makes steam appear denser. Wind may lift vapour into columns or drive it close to the ground, hiding vents, people and parts of the route.

Snow covers many subtle mineral colours while increasing the contrast between white ground, dark mud and rising steam. Thin snow may melt around warm areas and reveal irregular patterns of heat at the surface.

Low cloud can enclose Hverir and separate it from the surrounding mountains. Clear weather places the field beneath Námafjall and within the larger Mývatn–Krafla landscape.

Even a short visit may contain several versions of the same place. The steam never remains still long enough for the view to become permanent.

Protection and Responsible Access

Geothermal landscapes can appear barren, but that does not make them resistant to damage.

The clay surface is soft, easily marked and slow to recover. Footprints beyond the paths can remain visible long after the visitor has gone. Repeated shortcuts widen into unofficial tracks and encourage others to follow.

Leaving the marked route creates two risks: it damages the geothermal surface and places the visitor above ground that may be dangerously hot or unstable.

Drones must be used according to current regulations and local restrictions. Even where flying is permitted, wind, steam and other visitors make Hverir a difficult environment. A drone disappearing into a plume may lose visual contact at the same moment wind pushes it towards people or geothermal features.

Equipment, tripods and clothing must also remain on the established route. The absence of vegetation does not mean there is nothing to protect. Hverir is a visible section of an active system, and the altered ground itself is the subject.

• • Námafjall means “Mine Mountain,” a name derived from historic sulphur extraction.
  • Námafjall is the ridge; Hverir, also called Hverarönd, is the geothermal field east of it; Námaskarð is the pass at its northern end.
  • Námafjall reaches approximately 485 metres.
  • The area belongs to the Krafla volcanic system.
  • Fumaroles form where steam and gases escape through openings in the ground.
  • Mud pools develop where geothermal alteration has transformed volcanic rock into clay and gas rises through the wet material.
  • Sulphur compounds, oxidised iron and altered rock contribute to the yellow, red, white, brown and grey colours.
  • The characteristic smell is primarily caused by hydrogen sulphide.
  • Some prominent stone-covered steam outlets are constructed vent features rather than natural volcanic cones.
  • Icelandic sulphur exports are recorded from at least the 13th century.
  • Sulphur was important in gunpowder and became a valuable export commodity.
  • Mining took place east of, on and north of Námafjall, but few obvious physical remains survive.
  • Renewed production was attempted through the Innréttingar programme in the 18th century.
  • Jónas Hallgrímsson examined the mines and processing methods in 1839.
  • A sulphur factory was built at Bjarnarflag in 1938, burned in 1939 and was rebuilt, but production was short-lived.
  • Hverir changes visibly with rain, dry weather, wind, temperature, snow and steam direction.
  • The ground-level route suits most visitors, but the ridge is a separate, steep walk over loose ground.