Háleyjabunga is a small picrite lava shield on SE Reykjanes. The main crater, sitting on top of Háleyjabunga, is circular in shape and 25 m deep. Picrite is a strongly porphyritic olivine-rich basalt. Abundant greenish olivine crystals are easily seen in hand specimens. Picrite lava shields on the Reykjanes peninslula are formed in early postglacial time, predating the more common olivine tholeiite lava shields.
Háleyjabunga is one of eight known picrite lava shields on the peninsula.
Magnús Á. Sigurgeirsson, 2010