It erupted in 2500 BP in the southern part of the Krafla fissure swarm.[1] The crater is approximately 1 km in diameter.[2]
Tephra has been carried from Hverfjall all over the Mývatn area. A landslide apparently occurred in the south part of the crater during the eruption, which accounts for the disruption to the round shape of the mountain.[citation needed] During the Age of Settlement, lava flowed from Svörtuborgir [ˈsvœr̥tʏˌpɔrcɪr̥], at the southern end of Námafjall [ˈnauːmaˌfjatl̥], around Hverfjall, which was nearly engulfed by the lava. At the same time an eruption occurred in the slopes above the valley of Hlíðardalur [ˈl̥iːðarˌtaːlʏr̥].[citation needed]
The rim of the crater is only accessible by two paths, from the northwest and south. It is strictly forbidden to use other routes in ascent or descent.
