four (or five) volcanic regions are called:
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
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:
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