We relate the Reykjanes Peninsula to the Reykjanes Ridge. It is so obvious that the peninsula is a continuation of this part of the huge Mid-Ocean Ridge of the Atlantic. But looking below the crust, things become somewhat different. The convection rolls of Reykjanes are subducted by the Kolbeinsey Ridge Convection Rolls, and therefore the magma now flowing as lava at Fagradalsfjall is not the same as that of the main part of the Reykjanes Ridge.
The subduction can be shown graphically as here below:
The two systems of convection rolls intersect between 60.7°N and 67.3°N, and the northern rolls are found over the southern ones.