Intro: Iceland is a land of ice and fire. Not only is it one of the most breathtaking places in the world to visit, but it is also one of the most unique geological sites to study. I recently co-organized and participated in a field trip to Iceland and Sweden as part of our university’s Society of Economic Geologist Student Chapter (check out the video here!). In this multi-part series I will give a quick summary and self-guide on how to get the most out of a visit to Iceland by seeing the amazing country though the eyes of geologist in order to help you understand and appreciate just how (geologically) unique Iceland is! On our route we traveled clockwise around the island, and cut through the middle. Thus, the multi-part series is broken as follows.
Part 1: A Land of Ice and Fire*
(Intro to Iceland, Reykjavík, the Golden Circle, Snæfellsnes Peninsula)
Part 2: Volcanic Landscapes of the North
(Mývatn, Dimmuborgir, Krafla, Námafjall, and Askja)
Part 3: Glaciers and Volcanoes of the South
(Nornahraun 2014/15 lava field, Central Highlands, Landmannaluagar, Laki, Vík)
*Disclaimer; Yes I am a Game of Thrones fan, so the there may be some references to this within the post series, as they filmed a large portion of the show in Iceland.
Part 1: A Land of Ice and Fire
Brief geological setting of Iceland
The reason that Iceland is so unique is because it is centered on the Mid-Atlantic Ridge, which is an active spreading rift of two large continental plates; the North American Plate and the Eurasian Plate. As the tectonic plates move apart, magma rises up resulting in basaltic volcanism. The oldest rocks are 16 million year old (Ma), but most of rocks are less than 3 Ma (Moorbath et al., 1968).
From Reykjavík to the Golden Circle
The capital city of Iceland is Reykjavík, and from there the most accessible and popular destination is a tour of the Golden Circle. On the Golden Circle route is the impressive Gulfoss (foss = waterfall) and the geothermal field containing Geysir and Strokkur. This is actually where the word geyser comes from!
The water in the geothermal fields is alkaline, and the hot spring eruptions are driven by heat from a magma body ~ 2 to 3 km beneath the surface (Waltham, 2000). The hydrostatic pressure (i.e., pressure from the overlying water column) causes the water to boil at temperature over 100°C at depth, where it is converted to steam. The decreasing pressure with proximity to the surface results in flash production of steam from the superheated water which drives the explosive eruption every ~ 10 minutes!
Next along the Golden Circle is Þingvellir National Park. This is arguably the most famous geological place in Iceland, as it is the northeast-elongated graben that represents the Mid-Atlantic ridge. It is the only above-water expression of the Mid-Atlantic Ridge, i.e., the rift that is pulling apart Iceland to this day! This area has been extensively studied and provides exceptionally clear evidence for continental drift and plate tectonics. It is also makes as neat photo as here you can “stand on” part of North America and Europe.
The Snæfellsnes Peninsula
The Snæfellsnes Peninsula is the western section of what is known as the Snæfellsnes Volcanic Zone. This is an intriguing area of island, as it is west-striking zone of intraplate alkalic volcanism that is off-rift to the main north-striking central volcanic axial rift system (Sigurðsson, 1970). On our trip we were joined by the Icelandic volcanologist Haraldur Sigurðsson (head of the Volcano Museum in Stykkishólmur which is definitely worth a visit). There are many interesting geological features to see, so I will just highlight several prominent ones we visited as we drove from Stykkishólmur counterclockwise toward the western end of the Peninsula.
Heading west from Stykkishólmur, a famous (and well photographed) mountain is Kirkjufell mountain. Differing from the volcanoes, this mountain is actually intermixed with glacial and interglacial-stage sedimentary rocks full of fossils, as well as layers of lava (Thordarson and Höskuldsson, 2002; Denk et al., 2011).
At the western edge of the Snæfellsnes Peninsula resides Snæfellsjökull. Snæfellsjökull is a stratovolcano located on the western tip of the peninsula; an infamous volcano featured in Jules Vernes’ Journey to the Centre of the Earth. This stratovolcano is 1446 km high and capped by the Snæfellsjökull glacier. It has produced both felsic and mafic volcanics. Products of the volcano shape the landscape on the western end of the Snæfellsnes Peninsula. The volcano has had several large eruptions that dispersed rhyolitic tephra over parts of the Snæfellsnes Peninsula, and well as smaller basaltic flows from fissures related to parasitic vents at the foot of the volcano (Kokfelt et al., 2009).
Lastly, a visit near the Djúpalónssandur is necessary to see some “magical” and bizarre rock formations.
The lavas here are a great example of the unique alkali lavas that compose the Snæfellsnes Peninsula. Alkaline rocks have an excess amount of alkali content (i.e., Na2O and K2O) over silica (SiO2). They are rarer than their sub-alkaline counterparts, which are the dominate lavas that make up the rest of Iceland, and most other igneous rocks in the world. The rock types seem at Djúpalónssandur and Hellnar are mugearite and benmoreite. Due to their higher silica content, beautiful flow banding can be seen in the grey lava. The dark (black) rocks represented parts of the lava that cooled very fast and are glassy, and the red lava represents oxidized lava that interacted with water.
Final thoughts: From the moment you land in Iceland you can sense something is very special about this place. It is nice to be able to understand a bit more about the dramatic geological processes that shaped such a spectacular land. Because most people fly into Reykjavík, a tour along the Golden Circle is one of the easily accessible things to do, and definitely a good place to start your adventures in Iceland. The Snæfellsnes Peninsular is not too far away either (~2 hour drive north) and offers a beautiful landscape in the shadow of the mysterious Snæfellsjökull stratovolcano, and a landscape shaped by some odd geological processes compared to the rest of Iceland.
Next up in my “how to explore Iceland through the eyes of a geologist” series will be Part 2 – Volcanic Landscapes of the North. Here resides the youngest rocks in Iceland (i.e., < 1 year old), as well as a terrain that look truly out of this world!
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Table of Icelandic Geology Terms
|á (s) ár (pl), fljót (large river)||River|
|aur (glacial outwash)||Sandur|
|bjarg (s), björg (pl)||Cliffs/Rocks/Crags|
|borg (s), borgir (pl)||Rocky hill|
|eldborg (s), eldborgir (pl)||Lava ring|
|fjall (s), fjöll (pl)||Mountain|
|vatn (s), vötn (pl)||Lake|
|víti (also used for explosive volcanic craters or maars)||Hell|
|völlur (s), vellir (pl)||Field/plain|