Magic Magma

Iceland is unique among nations because nearly all of its geothermal power production is located directly within an active plate boundary zone. The country stands astride the northern section of the Mid-Atlantic Ridge, where the North American Plate and Eurasian Plate slowly drift apart.

Within this environment, geothermal activity is not isolated. Instead, it forms part of a large interconnected tectonic and volcanic framework extending from the Reykjanes Ridge in the south to the volcanic systems of northeast Iceland.

The seven geothermal power stations producing electricity in Iceland are therefore much more than industrial facilities. Together they outline the geometry of the active volcanic belts of Iceland itself.

The Hengill Geothermal Complex

The largest concentration of geothermal power production in Iceland is found at Hengill, one of the most active volcanic systems in southwest Iceland.

Hellisheiði Power Station

Located on the southern side of the Hengill volcanic system, Hellisheiði Power Station is the largest geothermal power station in Iceland. It produces both electricity and hot water for the Reykjavík metropolitan area. Steam rises from wells drilled deep into fractured volcanic rocks directly above the active rift zone.

However, it is noticeable that Hellisheiði Power Station is not situated exactly above the tectonic division line between the plates, but slightly offset along the mantle convection rolls division lines interpreted in the area. These red upwelling lines, associated with the second and fourth convective layers, being rather evenly distributed between approximately 120 and 670 km below Earth’s surface, form the boundary between the Reykjanes Oblique Rift Zone and the West Volcanic Zone.

In this respect, the location of Hellisheiði resembles that of Svartsengi Power Station, as both are positioned along opposite sides of the same convection-roll framework.

Nesjavellir Geothermal Power Station

Situated near Þingvallavatn, Nesjavellir Geothermal Power Station occupies another section of the same tectonic environment. Together, Hellisheiði and Nesjavellir form the largest continuous geothermal utilization area in Europe. The two power stations largely make use of the same geothermal resources associated with the Hengill Volcanic System.

The location is highly significant geologically. The Hengill region lies exactly where volcanic activity, tectonic spreading, and large-scale fracture systems intersect.

Reykjanes Peninsula — Directly Above the Plate Boundary

The geothermal stations on the Reykjanes Peninsula are perhaps the clearest examples in the world of energy production directly tied to an exposed oceanic rift zone on land.

Svartsengi Power Station

Svartsengi Power Station became internationally known because of the nearby Blue Lagoon. However, geologically it is equally fascinating. The station extracts geothermal fluids from highly permeable volcanic formations created by repeated rifting episodes.

The intersections between the tectonic division line of Iceland and the interpreted convection-roll division lines are particularly apparent in this area.

Reykjanes Power Station

At the southwestern tip of Iceland, Reykjanes Power Station operates in one of the most tectonically active environments in the North Atlantic. Here, geothermal reservoirs are strongly influenced by seawater interaction and high-temperature magmatic systems beneath the peninsula.

The recent volcanic activity on Reykjanes has demonstrated how dynamic this part of Iceland remains.

Northeast Iceland — Rift Volcanism and High Heat Flow

The northeastern volcanic zone contains another cluster of geothermal power production associated with active crustal spreading.

Krafla Power Station

Krafla Power Station stands within one of Iceland’s most famous volcanic systems. The eruptions and rifting events of 1975–1984 transformed scientific understanding of how magma intrusions accompany plate spreading. A central hub, where several interpreted convection-roll division lines intersect within a comparatively small area, coincides with the geothermal activity associated with Krafla, Bjarnarflag Power Station, and Þeistareykir Power Station.

All of these three power stations are located slightly west of the tectonic division line, in apparent association with the mantle convection-roll division lines.

Bjarnarflag Power Station

Located near Mývatn, Bjarnarflag was one of Iceland’s earliest geothermal power stations. Though relatively small, it occupies an extremely important geological setting along the active rift.

Þeistareykir Power Station

Þeistareykir is one of Iceland’s newest geothermal developments. The area had long been known for extensive geothermal manifestations, but only in recent years has large-scale utilization become possible.

A Geological Pattern

What makes these seven power stations especially interesting is their apparent relationship both to the tectonic division line between the North American and Eurasian plates and to the interpreted divisions between the modeled mantle convection rolls mapped here. They are not randomly distributed across the country. Reykjanes Power Station and Svartsengi Power Station are found at the western end of the Reykjanes Peninsula, closely associated with the plate boundary zone itself.

In addition, Svartsengi appears to coincide with two downwelling lines associated with the second and fourth convective mantle layers. As mentioned before, these four modeled layers are interpreted as being rather evenly distributed between approximately 120 and 670 km below Earth’s surface.In many ways, the geothermal power stations themselves appear to reflect the tectonic framework of Iceland.

The pattern also illustrates a broader geological principle: geothermal energy is fundamentally linked to large-scale heat transport within Earth’s crust and upper mantle. Iceland simply exposes this relationship more clearly than almost anywhere else on Earth. For that reason, Iceland remains one of the world’s most remarkable natural laboratories for studying mantle processes, crustal spreading, volcanism, and geothermal systems.

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To Clarify: Mantle Convection Rolls and the Geological Framework of Iceland

May 11, 2026 Steingrimur Thorbjarnarson

Here is a good way to take a first look at how the mantle convection-roll system beneath Iceland works:

The convection rolls, once incorporated into a model of Iceland and the layers below it, appear to explain much of the country’s main geological framework. It is easiest to begin with the uppermost layers, since they likely have the most direct influence on the tectonic plate above. Here, a section is shown with reference points A and B. We can then focus on four distinct convection-roll sections.

The first roll, extending from the Kolbeinsey Ridge, corresponds closely with the West Volcanic Zone and the Reykjanes Volcanic Zone, eventually meeting the Reykjanes Ridge system of rolls at the southwestern corner of the country.

The second roll passes beneath the northern part of the North Volcanic Zone and extends toward the center of Iceland, framing the Central Volcanic Zone. It also aligns well with the South Iceland Seismic Zone.

The third convection roll is situated beneath the complex formed by the southern part of the North Volcanic Zone, the East Volcanic Zone, the South Iceland Volcanic Belt, and the Westman Islands volcanic system.

The fourth roll, located near point B, appears to provide the conditions necessary for the Öræfajökull Volcanic Belt.

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The Geologically N-American Part of Iceland

May 10, 2026 Steingrimur Thorbjarnarson

The tectonically N-American part of Iceland. Different aspects of seismic and volcanic activity explained.

The volcanic activity of Iceland can be examined by emphasizing the role of the North American side of the plate boundary system. In general, the North American Plate lies west of the mid-ocean ridges, the Kolbeinsey Ridge north of Iceland and the Reykjanes Ridge south of it. Iceland, however, is different, because two regions appear to transfer the volcanic activity eastwards. This is commonly explained simply by referring to a mantle hotspot beneath Vatnajökull, but here the process is interpreted somewhat differently.

According to this interpretation, convection rolls in the mantle layers beneath the tectonic plate contain both upwelling and downwelling sides. At the latitude of Iceland, the volcanic activity shifts eastwards from one side of the convection rolls to the other. Instead of forming a simple linear ridge, volcanic zones develop because the convection-roll structure interacts with the tectonic forces associated with the overall westward drift of the North American Plate. This interaction results in a broader rifting process and the formation of distinct volcanic and seismic zones across Iceland.

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The Symmetry of the Equatorial Mid-Atlantic Ridge

May 9, 2026May 9, 2026 Steingrimur Thorbjarnarson

The equatorial symmetry of the Mid-Atlantic Ridge

What is special about the equatorial section of the Mid-Atlantic Ridge? This segment extends across roughly one third of the distance between South America and Africa along the equator — approximately 20° of longitude within the roughly 60°-wide Atlantic Ocean at equatorial latitudes. The geometrical midpoint of the Atlantic at the equator therefore lies near 21°W, with about 30° extending westward to the coast of South America near 51°W and about 30° eastward to the African coast near 9°E.

When examining the zigzag geometry of this section of the Mid-Atlantic Ridge, an additional symmetry appears. The major deviations toward more northerly and southerly alignments occur at approximately equal distances from this central point, around 9° to either side. If one considers a basic upper-mantle convection-roll width of roughly 1.5°, together with a broader large-scale equatorial spacing pattern of about 30°, the geometry becomes particularly intriguing.

Naturally, this section of the Mid-Atlantic Ridge has been studied extensively using the full range of modern marine geophysical methods. The individual segments and fracture zones are well mapped and documented. Two of the most prominent equatorial fracture zones are the St. Paul Fracture Zone and the Romanche Fracture Zone, which together form a striking en-echelon pattern along the equatorial Atlantic.

To realize the importance of the equator, the most basic map of convection rolls division lines can be added:

Basic convection rolls system – main lower mantle upwelling lines

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Seven Geological Chapters Along the Northern Half of Iceland

May 9, 2026May 9, 2026 Steingrimur Thorbjarnarson

We can describe the route across North Iceland with reference to the map and its division lines. Note that the convection roll leading from Reykjanes Ridge main section is slightly coloured with yellow. Imagine setting out from Borgarnes in polygon 1 and driving up across Holtavörðuheiði. The road runs parallel to the division line until reaching the center of polygon 2, where it then turns directly north into Hrútafjörður. From there, the route bends toward the northeast, following the division line until arriving at the northern corner of polygon 3, where the road turns toward Blönduós.

The road onward into Skagafjörður curves repeatedly before turning inland, eventually entering Öxnadalur precisely at the boundary line adjoining polygon 5, the same line that defines the principal axis of the Reykjanes Ridge, continuing all the way to Akureyri.

From Akureyri to Mývatn, the main direction once again runs parallel to a division line, crossing one polygon, and thereby the other convection roll of the Reykjanes Ridge, from one side to the other (no. 6). To continue from Mývatn toward East Iceland, the route first heads directly east across a small polygon that appears to exert a major influence on the geology of the region. Beyond this point, the road follows the boundary of polygon 7 (the next convetion roll) until reaching the highlands of East Iceland.

Roads are, of course, constructed independently of geology or geological principles. Nevertheless, the landscape itself strongly influences where it is most practical to build them. If the boundaries formed by mantle convection rolls are indeed real, then they reveal themselves in various ways across the terrain. With this in mind, one may consider, while travelling from one region to another, which geological processes and structural influences may have shaped the environment within each individual section of the journey.