A monogenetic volcanic fissure (2 km) with scoria and spatter craters, rugged lava formations (20 sq. km), lava tubes and remains of human activities. The eruption was an integral part of Reykjanes Fires, a volcano-tectonic episode in 1210-1240.

A large cluster of late Ice Age hyaloclastite mountains, including a prominent lava shield (Kistufell), lined with Holocene but prehistoric volcanic fissures. A high-temperature area is located in the northern part, where sulphur was mined around 1880.

Three lakes in the hylaoclastite Ice Age ridges Vesturháls and Sveifluháls, containing groundwater. Djúpavatn is partly a crater lake, close to Djúpavatnsleið road, Spákonuvatn crater lake to the Sog-geosite and Arnarvatn to a marked path across Sveifluháls.

The grassy field, Höskuldarvellir northwest of Grænadyngja and Trölladyngja is bordered in the northeast by a large, prehistoric monogenetic scoria and spatter cone. It has been utilized as a gravel mine, thus damaged. Steam vents line the surroundings.

A prehistoric, volcanic fissure cuts into the slopes of Geitafell, a hylaoclastite table mountain. Out of five craters, made of scoria but chiefly of spatter, one is by far the highest, with a prominent lava channel branching off to the east.

A 10-km-long row of scoria and spatter cones in off-set (en echelon) sections, with centrally placed geothermal features and a borehole. It dates from a volcano-tectonic episode in 1210-1240 (Reykjanes Fires). The lava flow covers 20 sq. km, with remains of human activities.

Steep hyaloclastite mountains west of Sog – geosite. Geothermal sites and younger volcanic fissures border them, associated with various lava flows, including Afstapahraun (aa type)

A long line of sheer sea lava cliffs south of the old fishing hamlet of Hafnir. Various marine birds nest at the cliffs. A walk to Hafnaberg is popular among hikers and bird watchers, along a marked path from the road to Reykjanes.

A small, flat lava shield with a large, 20 to 25-m-deep crater. At least 9,000 years old, it was formed during a highly effusive lava eruption. The basalt-type is a primitive deep-mantle derived picrite that contains much of the green mineral olivine.