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The Eastern Volcanic Rift Zone is unique and shows the interplay between tectonic drift and rift process. The rifting is perpendicular to the tectonic drift.

The drift in the western half is slightly faster than in the eastern half. The drift vectors tend to be perpendicular to equatorial convection rolls, and thereby the vectors are aligned along the polar convection rolls. Information about the measurements of tectonic drift is found here: https://www.lmi.is/static/files/utgefid_efni/Maelingar/isnet_endurmael_2016_skyrsla.pdf

This picture is found on a sign in the middle of the Eldhraun Lava Field which did flow in the year 1783.

The Mývatn area is on the plate boundary of North Iceland. In addition, special stress from below is added by mantle currents. Steam leaks from the groun all around the road leading to the Mývatn Nature Baths.

Exceptional activity as found near Mývatn can be explained, as seen on the map below.

North-east of Mývatn is a geothermal wonderland, that can only be explained with this line of mantle convection underneath. The line is of double nature, because it both stands for division between small rolls of upper mantle, and also that of the large scale rolls of lower mantle. Mývatn is located directly over the big convection rolls responsible for creating the Atlantic Ocean.

Reykjanes Oblique Rift Zone is one of the most geologically complex areas in Iceland, because it has interwoven volcanic and seismic zone. The strike-slip faults of the seismic zone form due to pressure from SW and NE, whereas the volcanic fissures open when rifting occurs because of pulling from SE and NW. The polygon forming the main part of the Reykjanes Peninsula explains this. Therefore, we can see that different layers of convection rolls can affect the same area simultaneously.

A map from ISOR has been inserted at the lower right corner to show how the volcanic zones form perpendicular to the drift of the North American Tectonic Plate on one hand, and the opposite small scale effect of the eastern Reykjanes Ridge Convection Roll on the other hand.

The local rifting due to effect of opposite magma flow of the convection current below is found on bothe sides of the division line between N-America and Eurasia, drawn as curved black line through the polygon of Reykjanes Peninsula.

Red lines indicate up-welling division between convection rolls, blue lines are for down-welling.

The fjords in North Iceland are rather large and wide. They look at first as randomly distributed with various shape. Comparing with the convection currents underneath, the pattern is not random at all. The convection rolls division line extending from the Reykjanes Ridge marks the three eastern fjords of Eyjafjörður, Skjálfandi and Öxarfjörður. The crossings between that line and the other equator lines of the next layer below mark the estuary of the relevant rivers flowing into the fjords. The next division line north of the Reykjanes Ridge line works in the same way, marking Hrútafjörður, Húnafjörður and Skagafjörður. The result is a ladder-shaped pattern for the fjords, when compared with the mantle convection rolls underneath.

The two layers forming the surface in this way (with help from the glaciers above during the ice age) are actuallly the subducted convection rolls, at this latitude only found close to 410 km depth. How can the upper rolls be a secondary factor? Actually they also have their say. The lower set of convetion rolls at the north coast seem to have a certain degree of coupling, and therefore the Tjörnes Fracture Zone mainly follows the division lines of those lower layers. In the same way, the lower layers have this effect on large scale formation of topography of the North of Iceland.

One of the geological mysteries noticed is the Hudson Bay Arc. It is quite perfectly shaped, but the reason is not known. The edge of the Icelandic shelf platform is also an arc, but under the surface of the ocean, so it is less noticed on maps.

As can be seen on the maps, the arcs are identical. It does not necessarily mean that the two topographical / bathymetrical features are originally formed in the same way.

I have already examined the Icelandic Arc in detail in other posts. The Hudson Bay Arc is much more difficult to study, but this might be a clue for others to investigate further. https://magicmagma.com/2020/03/04/the-symmetry-of-iceland-around-the-reykjanes-ridge/

See also: https://www.mentalfloss.com/article/609355/geological-formations-baffle-scientists