Njörður Caldera is found within the Reykjanes Ridge:
The Reykjanes Ridge resembles a volcanic zone, as we see in Iceland. The volcano is found at a special location, where the upper most polar convection rolls division line does approach the division line between the equatorial convection rolls, responsible for the southern half of the Reykjanes Ridge. The faults stretching northwards from the caldera enter a micropolygon, shaped by four convection rolls layers.
The Reykjanes Ridge Polar Upper Mantle Rolls Division Line is up-welling, and works agains the drift direction of the North American Tectonic Plate, resulting in similar rifting process as within the volcanic zones of Iceland.
The Large Scale Lower Mantle Rolls are found deeper below, that is at 410 km depth. The Polar Upper Mantle Rolls upper limit is at 120 km depth, where the tectonic plate (the ductile part of it) meets with the convecting mantle.