The volcanic activity of the past two million years includes the Skagafjörður volcanic zone, active from 2 million years ago to about half a million years before present, but now extinct.
Árni Hjartarson wrote his PhD thesis about this area, and in his essay this map is shown:
file:///C:/Users/Lenovo/AppData/Local/Temp/Arni-Hjartarson-2003-PhD-heil-1.pdf
The form is in harmony with the other peripheric zones:
This line extending from the still active Hofsjökull caldera of the Central Icelandic Volcanic Zone, is found both by tracing the central axis of the outlines of the volcanic zone as drawn by Árni Hjartarson and the relevant points of the convection rolls grid.
Magic Magma 