The Ljósufjöll volcanic system at the eastern end of the Snaefellsnes Peninsula is composed of a group of alkali olivine basaltic cinder cones and lava flows along short fissures on a roughly 90-km-long WNW-ESE line.  The volcanic field is about 20-km wide at the eastern end and narrows to about 10-km width on the west.  The Ljósufjöll volcanic field contains the largest outcrops of silicic rhyolitic and trachytic rocks in the Snaefellsnes volcanic zone, erupted during the mid-to-late Pleistocene.  Youthful-looking cinder cones and lava flows with morphologically pristine surfaces as evidence of numerous eruptions during the Holocene.  The latest eruption at Ljósufjöll post-dated the settlement of Iceland, and took place about 1000 years ago.