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It can be useful to make a model. How do the two parts of Iceland drift apart? The system is double, but the main division line can be shown like this:

In this way, the role of the South Iceland Seismic Zone can be visualized more clearly.

During this decade, a few volcanic eruptions have been recorded under a glacier without breaking through the ice. It has occurred twice under Mýrdalsjökull in South Iceland, both in the year 2000 and 2011. These eruptions are comparatively small and last for a short time. The effect is usually limited to a flood, and in 2000 the bridge over Jökulsá River withstood the extra flow. On the contrary, the flood of 2011 took the bridge over Múlakvísl River.

The floods find their way under a glacier tongue, and this is a picture taken on the middle of Sólheimajökull where the flood of 2000 took place.

On the top, black basaltic sand and volcanic ash covers parts of the ice. The river Jökulsá flows peacefully down below.

The location of those two floods / eruptions are roughly pointed out on this map from Náttúrfræðistofnun of Iceland, with the convection cell grid added.

Knowing the position of convection rolls under Iceland, geological analysis becomes much easier. For our curiosity, we can examine the central points and find out which one is most central.

A few candidates appear. The Reykjanes Ridge has a central role for the Atlantic Ocean, but when it comes to Iceland the activity is transferred to the east. The large lower mantle convection rolls form a line from SW to NE under Hveragerði, and the relevant continuation of the circular path does also pass under Hveragerði, making it looking very centrally located. Still, the central role of the minipolygon near Hveravellir is exactly equadistance between Snæfell and Snæfellsjökull on the same latitude, and on the same longitude as Hekla and Eyjafjallajökull, giving it a special central role. The north part of the larger polygon is found to be the center of the Icelandic shelf, forming a surprisingly correct ellipse around the country.  Katla is a candidate for being most central compared to the tectonic drift vectors as measured with GPS technology.

Although the idea about hot spot is somehow challenged here, it can be mentioned that usually the hot spot of Iceland is thought to be underneath the western part of Vatnajökull Glacier. It really is a special area, where for instance Bárðarbunga has obviously a special role regarding forming dikes within the rift zone, along with Grímsvötn. The main volcanic zones connect there, so it plays a very central role.

For further reference:

A few different versions of central points 🙂

The two obvious volcanic spots of the globe, Hawaii and Iceland, are located on two of the main upwelling lines between convection rolls of the lower mantle.

On these small drawings it is pointed out how polygons along the main division lines are regarded as the center of the hot spots. Actually, the hot spots have to be understood by referring to the relevant division line between convection rolls.

Here it is shown that the lines of Hawaii and Iceland are exactly 120° apart.

The reason for the arch-like shape of the convection rolls is that moving objects can not flow directly on the rotating Earth. A moving particle travels along a circular path, as can be seen on weather maps. Now, when the mathematics of the relevant path of mantle currents are known, geology will never be the same again.

Actually, it has been noticed that compared with Earth’s center, Hawaii and Iceland form 90° angle.

On the division line between the N-American plate and the Eurasian plate lies the lake Laugarvatn in Southern Iceland. Baking bread in the sand at the side of the lake is an old tradition.

The bread has been in the boiling hot sand for 24 hours and is now fully baked.

The geothermal area is quite powerful. Look at the “border line” between the plates:

Clearly, this natural bakery is no usual place.

The “border line” with Laugarvatn.