Here's a site with information on where the lava is coming from.

https://www.volcanocafe.org/the-reykjanes-eruption-a-look-underground/

I've been wondering about the source of the lava, since the Mid-Atlantic Ridge is to the east. So is this new volcano the result of a hot spot, or what? The article explains.

The DH and I have been to north central Iceland, where tiny cinder cones about 15 feet high dot the landscape. It is an eerie place. In that place, Iceland is being split apart by the Mid-ATlantic spreading center.