Besides the parallel volcanic zones, WVZ and EVZ, and the NVZ, there are four volcanic zones outside rift zones, one of the extinct.
This map shows the drift direction, due to effect of layer 2, leading to rifting in Skagafjörður for a period of about 1 million years. Note the volcanic sites on the NS and EW axis. The two volcanic zones of Skagafjörður and Snæfellsnes became active around the same period of time, as the same drift mechanism to the SW caused enough tension in the areas for volcanic zones to develop. The drift vector is of course totally different than people are used to see, as the convection rolls system has hitherto not been known. Once taking the different factors into account, it becomes possible to understand the details of the tectonic drift history of Iceland and elsewhere.