[2] It forms the northernmost offset of the Bláfjöll mountain massif and is situated on top of the fissure system of Brennisteinsfjöll.

(Ari Trausti Gudmundsson, 2004),[4] whereas other scientists talk about the small plateau under the summit where the uppermost layers as basalt lavas.

[3] "Vífilsfell directly overlies" a tuya, called "Northern Bláfjöll" by Hamilton "and encompasses a conical mound of palagonite with isolated welded scoria, volcanic bombs, dikes with pillowed surfaces, and peripheral slump deposit".

The last eruptions in the Hengill system took place about 2000 years ago,[9] but the youngest lava field, the Svínahraunsbruni (Brennisteinsfjöll volcanic system) dates from the year 1000 and was also called Kristnitökuhraun, because at the time of the eruption, the Icelandic vikings had a dispute in Þingvellir about the question, if they should become Christians, to which, in the end, they acquiesced.

[3] One theory about their origin is, that during the last stages of Vífilsfell's eruptions, subaerial lavas had emerged up on the mountain, degassed there and then run into a deep lake or the sea.