The South Iceland Seismic Zone (SISZ) spans over 1.5° from the Reykjafell mountain at the side of Hveragerdi town in the west to the volcano Hekla in the east, along the 64th parallel. A sign at the side of the ring road (No 1) where a turn can be made to the Skeid area (road No 30). A sign is put up there with information about the SISZ and the earthquakes occurring there. The earthquake zone has been measured quite accurately and surprisingly many papers written about it https://www.researchgate.net/publication/290227094_Seismicity_Pattern_in_the_South_Iceland_Seismic_Zone.
If a seismic zone has two ends, some kind of framework must be causing it. The Southern Lowlands are trapped in between the North American Tectonic Plate and the Eurasian Tectonic Plate. A convection roll of the asthenosphere and upper mantle is found to span 1.5° from east to west, and the seismic zone fits into that pattern. Noticing this, was only the beginning of long-term studying, and now the shaping of the framework is quite clear. Convection rolls of different layers cross each other exactly at this location, forming division lines underneath. These divisions are actual in two ways, being affected by the rotation of the convection rolls below, and the horizontal pulling and pushing of the two large-scale tectonic plates.
The sign is important, and I wish more people could visit the site.
On the sign, it can be seen how the SISZ has a counterpart on the Reykjanes Peninsula. A lot can be learned from the SISZ, because its proportions can be exactly measured, and the results can then be used to understand the geology of other areas in Iceland and elsewhere.
Magic Magma 