It appears that these magma bodies exist beneath volcanoes over their whole lifetime, not just during an active state.' ...

These do not erupt violently and lava usually flows slowly out of them. Eruptions from volcanoes can be very dangerous. They can produce: Mount Fagradalsfjall in Iceland erupting. Magma ...

Instead, the lava there was likely dragged up directly from the mantle by a surge of hot, rocky material — known as a mantle plume — which created a reservoir of magma below the field.