Hverfjall has a large, circular explosion crater, about 140 metres deep and with a diameter of 1,000 metres. Hverfjall is one of Iceland’s most beautiful and symmetrical explosion craters, besides being one of the largest of its kind in the world. It is considered certain that the crater was created during a volcanic explosion, and its age is estimated to be around 2800 – 2900 years.
Tephra has been carried from Hverfjall all over the lake 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.
Hiking to the top of Hverfjall mountain is a popular activity. There are two paths up, one from the northwest and the other from south. It is strictly forbidden to use other routes or leave the paths, due to fragility of the nature. The hike up to the rim takes about 20 minutes, and once on top you will be rewarded with a beautiful view over Lake Myvatn, Dimmuborgir and the surrounding lava fields, especially when the sky is clear.