On March 29th, 1875, a violent eruption in the Dyngjufjoll Mountains finally marked the end of the Askja eruptions. This explosive eruption formed the crater Viti, north of Askja Lake.

In a pure explosive eruption, molten rock material (magma) is forced to the earth's surface, shattering into volcanic fragments (tephra) when it comes into contact with groundwater in lava channels. Ash from powerful explosive eruptions can be dispersed long distances - including to other countries, depending on winds. On the other hand, if the eruption is weak, crater walls of partially or fully solidified fragments are built up around the vent.

Since the end of the eruption, water has collected in Viti. Because of geothermal heat, the water is warm and quite suitable for taking a dip. Viti is 500 ft. in diameter and there is a distance of almost 200 ft. from the rim down to the surface of the water at the bottom of the crater. The water itself is around 26 ft. deep.