Hverfjall also known as Hverfell is a tephra cone or tuff ring volcano in the east of Mývatn, it is a circular explosion crater it is around 1 km in diameter and 140 meters deep. It erupted in 2500 BP. In the southern part of the Krafla fissure swarm.
Tephra has been carried from Hverfjall all over the Lake Myvatn 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.
The rim of the crater is only accessible by two paths, from the northwest and south, it’s a fairly easy hike around 4oo meters climb. It is strictly forbidden to use other routes in ascent or descent.