But actually, the Svínahraun is composed of 3 lava layers, all from the same volcanic system, the Brennisteinsfjöll, but from different times. The lowermost layer is the 5000 year old Leitahraun, in between is a 2000 year old lava, more or less from the same time as the eruptions in the neighbouring Hengill system, and the uppermost layer is the Kristnitökuhraun or Svínahraunsbruni emitted by the small craters Nyðri and Syðri Eldborg in the year 1000..