Tag: iceland

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Volcanic and Geothermal Activity along 64° N, Iceland

Steingrimur Thorbjarnarson

The 64th parallel intersects some of Iceland’s most significant volcanic and geothermal centers, including Hekla, Landmannalaugar, and Öræfajökull, which line up remarkably well along that latitude, about 3° of longitude apart. Let’s now trace the 64th parallel north (64°00′ N) carefully from west to east.

Tracing 64° N, Iceland

1. Western Start — Reykjanes Peninsula (22°–21° W)

The 64th parallel enters Iceland at the southern Reykjanes Peninsula, intersecting the Reykjanes Volcanic Belt, the onshore continuation of the Mid-Atlantic Ridge.

  • Key systems: Reykjanes, Svartsengi, Krýsuvík–Trölladyngja, Brennisteinsfjöll.
  • Geothermal activity:
    • Svartsengi (Blue Lagoon) — high-temperature field exploited for power and bathing.
    • Krýsuvík — intense fumaroles and sulfur deposits along faulted rhyolite ridges near Lake Kleifarvatn.
  • Volcanism: Basaltic fissure eruptions, most recently the Fagradalsfjall events (2021–2024), lie within a few kilometers north of 64° N.

2. Hengill and Hveragerði Region — Western End of SISZ (21° W)

At 64° N, the parallel runs just north of Hveragerði and crosses the Hengill volcanic system, a major geothermal center and the western terminus of the South Iceland Seismic Zone (SISZ).

  • Geothermal:
    • Hellisheiði and Nesjavellir plants utilize the Hengill field; production wells reach >300 °C.
    • Surface features include fumaroles, silica terraces, and mud pots in Hveragerði valley.
  • Tectonics: The SISZ runs eastward from here to Hekla (~19.5° W), spanning roughly 1.5° of longitude, as you noted.
    • It’s a transform zone, accommodating lateral spreading between the Western and Eastern Volcanic Zones.

3. South Iceland Seismic Zone (SISZ) — Between Hveragerði and Hekla (21°–19.5° W)

At 64° N, the line traverses the seismically complex Hreppar microplate.

  • Numerous NNE–SSW strike-slip faults and en-échelon fissures characterize this belt.
  • Though volcanic activity is minimal, earthquakes (M 6–7 historically) are frequent.
  • Geothermal springs occur near Flúðir and Laugarvatn, used locally for heating and bathing.

4. Hekla Volcano (19.7° W)

At precisely 64.00° N, 19.7° W, lies Hekla, Iceland’s most active stratovolcano.

  • Type: Elongate ridge volcano, 1491 m high.
  • Eruptive behavior: Mixed basaltic-andesitic, with both explosive and effusive events; last eruption in 2000.
  • Structure: A central fissure system about 40 km long trending SW–NE.
  • Geothermal: Weak surface manifestation; heat flux mainly magmatic.
  • Relation to SISZ: Marks the eastern terminus of the seismic zone and transition into the Eastern Volcanic Zone (EVZ).

5. Landmannalaugar–Torfajökull Region (18.8°–18.5° W)

Still right at 64° N, this area sits within the Torfajökull volcanic system, a vast rhyolitic caldera overlapping the Fjallabak fissure swarm.

  • Geothermal:
    • Active hot springs, mud pots, and steam vents along the Laugahraun lava and Brennisteinsalda area.
    • Surface temperatures reach >100 °C; deep hydrothermal systems exceed 250 °C.
  • Volcanic features:
    • Rhyolitic domes (Brennisteinsalda, Bláhnjúkur).
    • Mixed eruptions between Torfajökull and Veiðivötn fissure systems (e.g., 1477 AD event).
  • Significance: It’s one of Iceland’s largest silicic geothermal regions, directly intersected by the 64th parallel.

6. Veiðivötn–Bárðarbunga Fissure Swarms (18°–16° W)

Crossing the central highlands, 64° N passes just south of Veiðivötn, part of the Bárðarbunga–Grímsvötn volcanic system.

  • Recent activity: 1477 AD Veiðivötn eruption produced >5 km³ of basaltic tephra; the fissure extends ~100 km.
  • Geothermal: Subsurface high-temperature zones exist beneath Holocene lava fields; limited surface expression due to remoteness.
  • Topography: Alternating lava plains and crater rows — a direct result of fissure rifting at the EVZ’s central axis.

7. Northwest Vatnajökull Margin – Hamarinn & Kverkfjöll (16°–15° W)

Approaching the Vatnajökull ice cap, 64° N crosses areas where subglacial volcanism dominates.

  • Hamarinn (Loki): Central volcano beneath ice, source of jökulhlaups into the Tungnaá and Skaftá rivers.
  • Kverkfjöll (64.7° N, 16.7° W): Slightly north of the parallel but significant. Features:
    • One of Iceland’s most vigorous geothermal fields, extending under the ice margin.
    • Fumaroles, hot ice caves, and sulfur deposits at the ice edge.
    • Heat flow >1 W/m², indicating magmatic heat directly below.
  • Interaction: These subglacial systems release jökulhlaups, linking geothermal processes to glacial hydrology.

8. Öræfajökull Volcano (64.00° N, 16.65° W)

Exactly on the 64th parallel, Öræfajökull forms the southeastern corner of Vatnajökull.

  • Type: Stratovolcano; Iceland’s highest peak, Hvannadalshnúkur (2110 m).
  • Eruptive history: Catastrophic 1362 and 1727 eruptions, both explosive (VEI 5+), with ash fallout across Europe.
  • Geothermal activity:
    • Weak at the surface due to heavy glaciation, but meltwater and hydrothermal alteration indicate subglacial heat flow.
  • Structure: A large caldera, with geothermal vents beneath the ice—likely connected to a shallow intrusive complex.

9. Eastern Termination – Breiðamerkurjökull to Höfn (15°–14° W)

The 64th parallel exits Iceland across the southeast coastal plain and the Vatnajökull outlet glaciers.

  • Geothermal: Minimal visible activity; only low-temperature springs.
  • Volcanic: Ancient subglacial ridges and pillow lavas beneath the sands mark earlier Holocene eruptions under ice.

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Similarities between volcanic activity of Reykjanes and Snæfellsnes in Iceland

Steingrimur Thorbjarnarson

New seismic activity has been noticed at Snæfellsnes in Iceland. It can be compared with the present activity at Reykjanes where 10 eruptions have occurred since 2021.

The two volcanic sites, marked on the map, can be compared with the model of convection rolls related to the formation of the Reykjanes Ridge and Kolbeinsey Ridge. Together, they form the sections of the large Mid-Atlantic Ridge found south and north of Iceland. Within Iceland, several volcanic zones replace the mid-ocean ridge, and sometimes Iceland is described as a plateu on the top of the Mid-Atlantic Ridge. The largest volcanic zones, called the West Volcanic Zone, East Volcanic Zone and North Volcanic Zone, are not marked on the map.

Combining the ends of the said two ridge sections, it can be seen that the two volcanic sites have a similar position compared with the relevant line. The site of Snæfellsnes has not erupted yet, but it is known that magma intrusion is responsible for seismic activity there. The Icelandic Met Office has some information regarding the activity at the Snæfellsnes Peninsula:

.https://www.vedur.is/um-vi/frettir/jardskjalftavirkni-vid-grjotarvatn-aukist-undanfarna-manudi?fbclid=IwY2xjawH-bMdleHRuA2FlbQIxMAABHcDJq8FbbUQJgLtR-HuwIEBknE8PeNannviNIDSoX_yRzFvLqyz9J-HecQ_aem_rTwKR0cWgZa59dGwFw_gEg

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Reykjanes Eruption – where is the origin?

Steingrimur Thorbjarnarson

The tenth eruption on the Reykjanes Peninsula started suddenly on the Sundhnúkagígar fissure. All those eruptions are thought to be connected and considered to be one volcanic event, based on rather constant flow of magma from the interior. The model used here adds an explanation of the geophysical settings of the deep roots of the volcanic site. Two convection rolls division lines coincide under the point where the magma ascends. The lines cross the outer limits of the seismic zone at this location, providing a weakness in the crust.

Convection rolls model and site of ascending magma at Reykjanes Peninsula.

To understand how the system works according to the model, this drawning can be studied. The two layeres, with division lines between convection rolls found under the point of ascending magma, are marked here as source layer A and source layer B. Layer A is found at the depth of about 260 km, and layer B at 530 km depth (530-670 km). This means that magma of different types should be found, both from layer A and B. Besides that, the hot magma from below does partially melt the ductile part of the tectonic plate (commonly referred to as upper mantle found below the brittle crust).

The petrology of the lava should therefore be compared with these modelled preconditions of the eruptions. The three eruptions on Fagradalsfjall volcano and the seven eruptions on the Sundhnúkar fissure are originated from the same source, according to the findings in the article: The Fagradalsfjall and Sundhnúkur Fires of 2021–2024: A single magma reservoir under the Reykjanes Peninsula, Iceland? ( https://www.researchgate.net/publication/381756298_The_Fagradalsfjall_and_Sundhnukur_Fires_of_2021-2024_A_single_magma_reservoir_under_the_Reykjanes_Peninsula_Iceland

The authors of the article (Valentin R. Troll. Frances M. Deegan, Thor Thordarson, Ari Tryggvason, Lukáš Krmíček, William M. Moreland, Björn Lund, Ilya N. Bindeman,
Ármann Höskuldsson and James M. D. Day), come to this conclusion: “Whole rock and mineral geochemical data show that the
2023 SVL eruption produced lava compositions that, for the most
part, continue the trends established by the lavas of the late 2021 to
2023 Fagradalsfjall Fires (Figures 4 and 5). A first-order observation
is therefore that all of the recent FVL and SVL magmas are derived
from a similar magma source (excluding perhaps the early parts of
the 2021 Geldingadalir eruption), or a similar combination of sources,
which are different to the source(s) of previous magmas erupted on
the RP…”

Considering that, according to the model of convection rolls, it is quite likely that the uppermost division lines, oriented SW-NE, often provide magma from the mantle. This time it is probably not the case, as it seems likely that the source is from those deeper layers, because the relevant division lines are found exactly under the magma source location, which might explain different composition of the lava samples considered in the said article.

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The Eastern and Western Outposts of Icelandic Volcanoes – Snæfell and Snæfellsjökull

Steingrimur Thorbjarnarson

The two outposts of Icelandic volcanoes are both stratovolcanoes. They are outside the main volcanic zones, and do not fit with the most simplified version of Icelandic geology. One is too far to the west, the other too far to the east to match well with our most basic ideas about how Iceland is divided into its North American part and Eurasian part. The convection rolls model considered on this webpage is of course different, and according to the pattern emerging from the division lines between convection rolls, the positions become understandable. If there were no such reasons, such as convection rolls, the coincidence that those two mountains are exactly on the same latitude could not be explained. Of course it is easy just to ignore things like that, but these two volcanoes are both found on division lines between convection rolls, in a mirrored way.

It should also be mentioned that the distance from those two volcanoes to the main division line of the lower mantle, is exactly the same, when compared with the N-S axis of Hekla volcano. That means, of course, that the two Snæffells (Snæfellsjökull and Snæfell) are equidistant from Hekla. Such a coincidence can of course also be ignored, but according to this system of convection rolls, it is explainable, because Hekla does form on important crossings within the convection rolls division lines pattern. Different layers all have division lines under Hekla, four different convecting layers! The location of Hekla is therefore no coincidence, and the uppermost layer of mantle convection is upwelling underneath Hekla, making the location even more understandable. All over the world, countless similar patterns can be found, all in harmony with the convection rolls.

Snæfellsjökull, November 15th 2024.

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How volcanic and seismic zones interact in the Reykjanes eruptions

Steingrimur Thorbjarnarson

It is well known that the interplay between volcanic and seismic zones is at work on the Reykjanes Peninsula. The peninsula is being pulled apart by the same forces as shape the Mid-Atlantic Ridge, and that is by definition a divergent effect. This causes the volcanic fissures to open up, being aligned from SW to NE. The dykes responsible for the eruptions have the same alignment, being in the same direction as the model used here. It is important that a mathematical formula can be used to calculate alignment of volcanic dykes, and it also adds to the credibility of the theory that convection rolls are found underneath the tectonic plates.

The seismic area of Reykjanes is bent, but the seismic faults are oriented N-S within the bent area. In addition, the Reykjanes seismic area extends from the South Icelandic Seismic Zone. These two seismic zones are therefore connected, and the connection point is also the point connecting two polygons of the convection rolls model. The Reykjanes seismic zone is formed due to compression of the area, perpendicular to the extension due to the divergent effect of the Mid-Atlantic Ridge. These pressure vectors are quite comparable to those of the South Iceland Seismic Zone.

What makes the Reykjanes Seismic Zone special is the fact that it is bent, making it possible to connect the Reykjanes Ridge and the South Iceland Seismic Zone. The two different forces therefore become compatible, resulting in a wholistic and logical drift system.

Superimposed blue line, showning mantle divisions, crosses the seismic and volcanic areas on the Reykjanes Peninsula, pointed out with an arrow on the map. Volcanic systems on the Reykjanes peninsula are shown in pink. The red lines indicate the tectonic plate boundary, where earthquakes are common. Geothermal areas are marked in yellow. Black lines indicate fissure swarms. Modelled division lines and the outlines of seismic zones are superimposed on a map base from ISOR.

The main active areas are found within the southern half of the bent seismic area, as it extends from the South Iceland Seismic Zone.

Comparing the model with the basics of the Oblique Rift Zone of Reykjanes does not explain the present activity to a full extent. On the other hand, it shows that the present event brings into light the combined effect of several factors, mainly the volcanic fissure swarms, the seismic zone, and the mantle rolls division lines.

A scientific approach to these three combined factors would be to compare them with petrological and seismic evidence, along with other information available about surface movements. That could answer many questions.

Not much is known about the source of this magma. It is only possible to trace its history with some degree of accuracy from the time when it is already being accumulated somewhere within the tectonic plate. The energy necessary to provide the magma is only found below the tectonic plate, and therefore the flow should be traced all the way down to the depth where convection can take place.