Reykjanes (The Steamy Peninsula) is the name of the south- westernmost tip of the country. The area is and looks very volcanically active and barren. The most conspicuous are the old shield volcanoes and the crater rows, which most probably were created in historic times.
There is much thermal activity and the nearby, powerful high temperature area has partially been harnessed to supply energy. The first lighthouse of the country was built on top of a low mountain in the area in 1778. It collapsed because of the sea erosion of its foundations and the present one was built in 1907-08.
A short distance off the coast a 52 m high rock pillar, called Karl (The Giant), protrudes from the ocean and further out stands the 77 m high rocky island Eldey, The Fire Island, with the world’s largest gannet colony (70.000 birds). In this area three islands have been created during submarine eruptions in historic times. They all disappeared soon after the eruptions ended. The distance from the capital is about 56 km
Its four (or five) volcanic regions are called: Fagradalsfjall area, Reykjanes-Grindavik-Vogar, Trolladyngja (often split into two regions), Krysuvik, Brennisteinsfjoll-Blafjoll and Hengill-Selvogur. The earthquake zone cuts through all four or five regions and is the source of frequent earthquakes and high temperature areas have been created within it, such as at Reykjanes (the heel of the peninsula), in the Eldvorp area, the Svartsengi area, the Krysuvik area and the Mt Brennisteinsfjoll area. All of those volcanic regions have delivered basaltic (tholoid) lavas to the surface during Holocene except the Hengill Area. Picrite is found in the old and smaller shield volcanoes and olivintholoid in the younger and larger ones. About 52% of the Reykjanes Area are covered with Holocene lava fields (43 km²). The structure of most mountains in the area is basaltic hyaloclastites. They were created during the latest cold epoch of the Ice Age.
The Reykjanes Zone is a so-called Rift Zone (thoelite). Earthquakes are frequent. About 16 lava fields have been created during historic times (875-1340) by 4-5 eruptions. The lava field near Lake Hlidarvatn dates back to 1340. The lava field Ogmundarhraun was created in 1150. The uppermost lava fields in the Blafjoll area were created shortly before the year 1000. The lava field Svinahraun could be the so-called Christianity Lava. The Svartahraun Lava, where the Blue Lagoon is situated, dates back to 1226. The Kapelluhraun Lava Field dates back to 1150. The Afstapa Lava Field was also created during historic times. The Stampa- and Arnarsetur Lava Fields were created in 1226.
The Fossvogur Strata are about 10 thousand years old. They depict sediments with fossilized seashells and conches from the second latest warm epoch of the Ice Age.
The Oskjuhlid hill in the capital depicts the geology of the latter part of the Ice Age. It was an island during higher sea levels 10 thousand years ago. Such traces are found 43 metres above the present sea level in the form of sea eroded moraines and boulders.
The Burfell Lava is about 7200 years old (C14), but could be somewhat younger because of the unknown inaccuracy of the C14 method.
The Thorsberg hill in Hafnarfiord is situated on an old coastline, which lies about at 38 m above the present sea level in the slopes of the hill Hvaleyrarholt, at about 48 m in the nearby town Gardabaer, and at 43 m in Oskjuhlid in the capital. These different sea levels were caused by the great weight of the ice shield. The Reykjanes Peninsula started rising earlier than the capital area because of the earlier retreat of the glaciation there.
The Kapellu- and Nyjahraun lava fields were created during the first part of the 11th century (1010-1020). In a lava stone ruin of a tiny chapel opposite the Aluminium Smelter a statuette of Holy Barbara was discovered. She is, among other things, the patron saint of travellers, geologists and alchemists. Large cold water spring areas are on both sides of the smelter.
Geologically interesting places and areas in the Southwest: Fagradalsfjall/Geldinadalir, Hengill Area, Svartsengi, Eldeyjarbodi, Festarfjall, Krysuvik, Reykjanes, Selatangar, Vatnsleysustrond, Thingvellir, Geirfuglasker, Breinnisteinsfjoll, Esja, Fossvogur strata, Island Videy, Blafjoll Area, Arnarseturshraun, Leitarhraun, Sulur, Raudamelur, Stapafell, Vogar, Seltjorn, Thrainsskjoldur, Hrutagjardyngjuhraun, Kapelluhraun, Nyjahraun, Trolladyngja, Ogmundarhraun, Oskjuhlid, Krysuvik.Craters Raudholar