Author: Steingrimur Thorbjarnarson

Looking at the grid formed by the division lines of the convection rolls, together with the division boundary within the tectonic plate itself, we can identify crossings located precisely where uplift is occurring.

Crossings Between Tectonic Division Boundaries and Mantle-Roll Boundaries on the Reykjanes Peninsula

The broad curvature of the tectonic division boundary extending from Hveragerði to the Reykjanes Ridge is mirrored around a point near the Blue Lagoon and Grindavík. This is also the area where the recent uplift center has developed.

Geologists have discussed why the uplift center is located close to the geothermal power plant, west of the Sundhnúkur crater row and the associated dyke intrusion system. Current observations indicate that magma initially flows eastward from the deeper reservoir before entering a dyke system aligned NE–SW.

However, when the mantle-roll division boundaries are included in the model, the geometry becomes easier to visualize. In this interpretation, one of the deeper mantle division lines is aligned NW–SE beneath the area. This alignment may provide a structural pathway guiding magma movement upward and slightly toward the southeast. After reaching shallower crustal levels, the magma flow then makes an approximately 90° turn and enters the NE–SW-oriented dyke system associated with the Sundhnúkur eruptions.

This arrangement suggests that the magma transport system may reflect the interaction of two different structural controls:

1. the deeper mantle convection-roll boundary system, influencing the initial ascent and lateral transport of magma, and
2. the shallower tectonic rift geometry of the Reykjanes Peninsula, which controls the orientation of the dyke swarm and eruptive fissures.

Seen this way, the location of the uplift center west of the crater row is not necessarily anomalous. Instead, it may represent the point where these two structural systems intersect most effectively, concentrating magma accumulation and crustal deformation in a predictable geometrical position.

The regular bow of tectonic division line from Hveragerdi to the Reykjans Ridge is mirrored around the point close to the Blue Lagoon and Grindavik. The point of uplift is therefore central to the system, connecting the Reykjanes Ridge and the so-called South Iceland Seismic Zone.

In the mantle there is a layer that explains the heat anomaly found under the glacier of Greenland. It has been calculated and is shown here above.

The lines are obviously approximately the same. Usually geologists regard Vatnajökull as the site of hot spot, so therefore someone has drawn the line over Iceland a little bit eastwards of the calculated division line between convection rolls.

https://nasaviz.gsfc.nasa.gov/cgi-bin/details.cgi?aid=13128&button=recent&fbclid=IwAR0BXeq2CQ8LUoDsCPqY84TGRg8Nq8X_o6lery_z1lEPcyVBcYpM-nSRyDY

Look at this site 🙂 and how it resembles the line.

This line represents the main division of the second row of convection rolls counted from above.

The National Geodetic Network of Iceland (ISNET) was measured for the third time in 2016. It shows how Iceland really drifts towards NW and NE.

To introduce this is quite important, as understanding tectonic drift is important to understand geology in general. The result is very clear and I recommend people to read the report carefully. Still, very few geologists seem to realize the new results, found after GPS measurements were used to find this out. Most geologists still think that the drift vectors are mainly to the east and west.

The report: https://www.lmi.is/wp-content/uploads/2019/09/skyrsla.pdf

This report is written both in Icelandic and English.

It is obvious that some kind of harmony is found between the rolls and vectors. When outside the rift zones, the match as close as it can get.

What is really noticeable, is the fact that the vectors of the eastern part have exactly the same deviation from nort as the vectors of the western part of Iceland. This mathematical mirroring around a NS-axis is fundamental, and is in harmony with the model of the convection currents of the mantle.

There are a few hotsprings in Iceland named Geysir. One is world famous and its name became used in general for spouting hot springs. The hot spring area of Geysir in Haukadalur of SW Iceland shows resemblance of Geysir at Hveravellir in the NE.

Here is a picture of the hot spring Strokkur in the area of Haukadalur.

Both Geysers are located close to the main division line of lower mantle.

The geothermal areas are known to have a distribution from SW to NE. The mantle division lines pattern is not known to almost everyone, so therefore this symmetry compared to the convectin rolls is shown here.

Near Mývatn are the high temperature areas of Krafla, Námaskarð and Bjarnarflag. At Bjarnarflag the Nature Baths are found.

The reason is a complicated network of division lines between convection rolls of different layear below the area.

At Námaskarð, very special formations are found like this one: