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The Dynamic Geology of Iceland

- Swedish PhD excursion to Iceland, 5-12/6 2005 -

NEW! Click here for a photo gallery from the excursion!

Welcome to the Swedish PhD excursion to Iceland, 5-12 June 2005. The satellite photo above (Image courtesy of MODIS Rapid Response Project at NASA/GSFC) shows southern and western Iceland, which will be the focus of our fieldtrip. Below you will find practical information on the excursion, the planned route, some geological highlights, litterature tips and useful web-links. I want to specially thank the distinguished photographer Mats Wibe Lund for giving me permission to use some of his excellent photographs of Icelandic landscapes, and refer people to his outstanding web-gallery at http://www.myndasafn.is/. Oddur Siguršsson also generously gave me permission to use some of his photos. Please do not download or otherwise distribute photos from this web page without written permission.

Geological map of Iceland
Geological map of Iceland, showing volcanic systems and bedrock formations. Source: Landmęlingar Ķslands.

Preliminary programme:

Sunday, 5th of June. Participants arrive in Reykjavķk. Lodging at the Reykjavķk Youth Hostel. This fine hostel is situated next-door to Laugardalslaug, one of the excellent outdoor swimming pools of Reykjavķk. Be sure to bring your swimming suite and bathing towel, we like to go for a swim every day. Easiest way to get to the Youth Hostel from Keflavik International airport is to take the airport bus. Tell the driver you will be lodged the Youth Hostel, and the shuttle will drop you off there. The current price for a one-way ticket is 1150 ISK (about 125 SKR). The ride from the airport takes about 1 hour. You will pass some beautiful lava fields on the way, and a number of volcanoes and hialoclastite ridges (formed by subglacial volcanism) form the mountain chain by the horizon south and east of the road to Reykjavik.

You will be met in the reception by Ólafur Ingólfsson, at ca. 19:00 on the 5th of June. We will take a walk (about 5 km) along the northern seashore of Reykjavik, downtown and to the Earth Science building at the University campus. There we will discuss the excursion programme, and have an introductory lecture on the geology and geography of Iceland.


Monday 6th of June. This day is devoted to rift tectonics and volcanism. We will head east from Reykjavķk, towards Nesjavellir geothermal area. It is located at the southern shore of Lake Thingvallavatn, close to the major central volcano Hengill. This is an active volcano complex, with at least one historical eruption. On the way we will make a couple of stops to look at products of subglacial volcanism and postglacial lavas. There is a major geothermal power plant at Nesjavellir, and we will have a guided tour through the plant. The route then goes along the shore of Lake Thingvallavatn to Thingvellir proper. The name means "Parliament Plains" and is the site of the old Icelandic legislative assembly, the Althing, first held in 930 AD. Thingvellir is a major rift valley, with extraordinary well developed rift-fissure systems that illustrate plate tectonics better than any textbook can. This is where the North American and Eurasian plates drift apart. The large and deep (114 m) lake is partly filled in by postglacial volcanism, and to the North we will have view of some spectacular glaciers and volcanoes, including the large Skjaldbreišur shield volcano. After a visit to a small Natural History exhibition, located at an overview site at the rim of the Thingvellir rift valley, we will walk down Almannagjį, one of the large faults at Thingvellir, and visit the Öxarįrfoss waterfall.


View across the western rim of the Thingvellir rift valley. Photo: Ólafur Ingólfsson, 2005

From Thingvellir, the route goes across a major shield volcano, Lyngdalsheiši, towards the Great Geysir area. On the way there are spectacular palagonite formations and lava fields - if the visibility is good, there is a clear view of the large highland ice cap Langjökull (an ice-capped volcanic complex, 1355 m), and the famous Mt Hekla (1491 m) volcano will dominate the south-eastern horizon. There are numerous fumerols and hot springs in the Great Geysir geothermal area. One hot spring, Strokkur, erupts every few minutes, but Great Geysir is presently dormant. This is one of the most active earthquake zones in Iceland, and large quakes sometimes wake up old Geysir. This happened in the summer of 2000, when the last major earthquake hit this part of Iceland.


Mt Hekla, southern Iceland. Photo: Hreggvišur Noršdahl, March 2005.

From Geysir there is only about 25 minutes drive to the magnificent waterfall of Gullfoss. Here, we will learn about the geology of the Hvķtį river canyon, and how rift tectonics control the river course and the morphological development. From Gullfoss the tour turns southwards, across the westernmost side of the Southern lowlands. En route there are beautiful landscapes shaped by subglacial volcanism, glacial erosion and postglacial volcanism. We will stop at Kerid, a water-filled explosion crater in a mid-Holocene lava field. From there we head towards Reykjavik, pass Mt Ingólfsfjall (with huge earthquake-generated rockfall-boulders littering the slope) and the town of Hveragerši. The town is situated in the middle of a large geothermal field, and is the centre of greenhouse-based growing of vegetables and flowers. Thanks to the geothermal water supply, greenhouses keep near-tropical temperatures through the year. They actually grow bananas in Hveragerši. On the final leg towards Reykjavik we will cross the northernmost part of the Reykjanes Peninsula south of the Hengill central volcano.  Where we cross, it is called the Hellisheidi highland, and is a beautiful landscape of extensive lava fields, active and extinct volcanoes and crater rows.

In the evening, if the weather is good and people feel up to it, we might take a city buss and visit a geological spot in Reykjavķk, either Fossvogur or Seltjarnarnes Peninsula. Both sites carry late glacial sediments and provide information on the deglaciation and relative sea level changes in the Reykjavik area. From Seltjarnarnes there is a spectacular view towards the conical central volcano of Snęfellsjökull across the Faxaflói bay.


View across University of Iceland campus in foreground and Seltjarnarnes Peninsula. Snęfellsjökull, a glaciated central volcano, at the horizon. Photo ©Mats Wibe Lund. Published to this web page with permission. http://www.myndasafn.is/

Tuesday 7th of June. Excursion to Hvalfjöršur and Borgarfjöršur fjords, western Iceleland. The focus of this excursion day is Plio-Pleistocene volcanism and glaciations, and last deglaciation and relative sea level changes. The route will pass below the slopes of Mt Esja (914 m), which dominates the horizon north of Reykjavik. Mt Esja is the result of Plio-Pleistocene volcanism, and contains basaltic lavas as well as gabbroic intrusions and rhyolite, numerous basltic dykes, clastic (volcanic and glacial sediments). The Esja succession covers about 1.3 million years, between 3.1-1.8 million years ago. We will visit a section at the base of Mt Esja, where clastic sediments of glacial or rockfall nature outcrop. Then the bus will drive along the Hvalfjöršur shore. This is a major ice-carved valley system, occupied by a large outlet glacier or ice stream during repeated glaciations.


Scenery from the inner part of Hvalfjöršur. Photo: Ó. Ingólfsson, 2005.

There will be a couple of stops on the way, to look at outcrops of Late Pliocene clastic rocks and the eroded remnants of a Late Tertiary major volcanic system, the Hvalfjöršur Volcanic Complex. These include dyke swarms, intrusion rocks and thick lava flows filling up an ancient caldera. Raised beaches formed by the end of the last glaciation will also be seen, as well as impressive signs of fairly young subglacial volcanism. After Hvalfjöršur the road will take us across the inner valleys of Hvalfjöršur to Skorradalur. Skorradalur is a glacially sculptured valley, occupied by a large and deep lake. Its surface is at 52 m a.s.l.


Skorradalur was a fjord by the end of the last glaciation, and some of the highest Lateglacial raised beaches in iceland occur where the valley opens into the larger Borgarfjöršur valley. These are from Bųlling times, ca. 12.6 ka BP. The best exposure is at Stóri Sandhóll, which is a marine terrace reaching 150 m a.s.l. It is a key location for understanding the dynamics of the last deglaciation of Iceland, illustrating very rapid ice retreat and isostatic rebound.


Stóri Sandhóll, a marine terrace of Bųlling age in Skorradalur. Behind, alpine scenery of the Skardsheiši massif. Photo: Ólafur Ingólfsson, 1998.

From Skorradalur, the route turns southwards, and the next stop will be the impressive end moraine ridge complex of Skorholtsmelar. They were formed at the terminus of a major outlet glacier coming down the large Borgarfjöršur valley. The moraine ridges reach about 100 m a.s.l., and carry both to the proximal and distal sides a well dveloped marine terrave at 60 m a.s.l.

Mt Akrafjall has divided ice streams coming from the east during the Pleistocene glaciations, and been an island during times of high relative sea levels by the end of the last glaciation. There are quite extensive flights of raised beaches and marine terraces along the mountain slopes, as well as beach cliff faces. We will visit a gravel pit in one of those beach deposits, and illustrate the high-energy beach environment there at the time of deposition.

On the way back to Reykjavķk, the road goes via tunnel under Hvalfjöršur. This tunnel is interesting, because of the high geothermal gradient associated with old dyke systems of the Plio-Pleistocene volcanic activity, rock temperatures at the lowermost point in the tunnel is +60°C. This warms the air and causes it to rise. In this way cold air is sucked in through the northern end of the tunnel and vented out at the southern entrance. A natural air conditioning system, in other words.

Wednesday 8th of June. The trip goes towards southern Iceland. Key sites here include the Bśši end moraine system of Younger Dryas and Preboreal age and associated raised beaches. Looming on the horizon will be the large central volcanoes of Mt Hekla, Tindfjöll, Eyjafjallajökull and Mżrdalsjökull. The trip will take us south of the Eyjafjallajökull and Mżrdalsjökull ice caps, to the Sólheimajökull outlet glacier, where we will study proglacial sandur outwash, neoglacial moraines, and recently (since 1995) deglaciated glacier forefield with flutes, drumlins and retreat moraines. Remnants of a minor jökulhlaup in 1999 (pitted outwash) as well as megaripples associated with major Holocene jökulhlaups in connection with large eruptions in the subglacial Katla caldera will be studied. The trip ends at Drangshlid farm, where we will be lodged for the next three days.


Sólheimajökull, an outlet glacier from Mżrdalsjökull ice cap. Photo: Oddur Siguršsson, 30. October 1985.

Thursday 9th of June. This day will be devoted to the area north of Eyjafjallajökull, towards Žórsmörk. We will visit Seljalandsfoss, a beautiful waterfall that comes of a marine cliff carved during higher sea level around 10 ka BP. The first major stop during the day will be at Gķgjökull. It is a very good site to study diverse dead-ice processes, sediments and landforms. The glacier, which is an ice-fall glacier that descends very rapidly from the top crater of the Eyjafjallajökull glacier/central volcano, is in retreat. A glacial lake occupies the proglacial basin, inside very large, ice cored moraines. The Eyjafjallajökull central volcanoe is relatively young, built-up during the past ca. 200 ka. During the last glaciation considerable amounts of intermediate and acid lavas were erupted. Only two eruptions are known in Eyjafjallajökull in historical times, both rather small. The first eruption occurred in 1612 AD, and the latter in 1821. During that eruption, a jökulhlaup came down the Gķgjökull channel.


Gķgjökull drains the Eyjafjallajökull caldera towards north. Photo:
Ólafur Ingólfsson, 2005

After a couple of hours stop at the Gķgjökull site, we will cross the Steinholtsį glacal river and go towards Steinholtsjökull glacier. A major rockfall in 1969, where the mountain slope above the glacier collapsed, has left spectacular rockfall debris.

The final destination for the day will be Žórsmörk. This is an oasis of vegetation and beautiful glacial and volcanic landforms, in a rain shadow behind the ice caps of Mżrdalsjökull and Eyjafjallajökull. Žórsmörk is surrounded by huge glacier/volcanic complexes: to the south is Eyjafjallajökull, to the east is Mżrdalsjökull, and to the north is Tindfjöll. Among geological highlights here is the Žórsmörk Ignimbrite. It was formed by a major eruption in Tindfjöll some 200-250 ka BP.


Žórsmörk scenery. Mżrdalsjökull in the background. Photo: Ó. Ingólfsson, 2005

Friday 10th of June. This will be a long day, with the easternmost destination of our trip at Skaftafell National Park, below the great Vatnajökull, and Breišamerkurlón. We will start the day by travelling east along the southern margins of one of the mightiest volcanos in Iceland, Katla, whose great caldera is buried below the Mżrdalsjökull ice cap. In Katla, there has been intensive volcanic activity with at least 17 eruptions in historical times. The number of pre-historical eruptions are not known but may approach 100. It has been estimated that as much as 30-35 km3 of tephra may have been produced from this area during the post-glacial time. Associated with the subglacial eruptions are enormous catastrophic jökulhlaups, which may reach water volumes of >300.000 m3 per second (for comparison, top discharge from Icelandic glacal rivers during summer melt rarely exceeds 500 m3 per second). During Katlas last major eruption in 1918, the shear volumes of debris carried by the jökulhlaup caused the coastline to move more than 4 km outwards. We will cross Mżrdalssandur, the huge outwash plane in front of Mżrdalsjökull, and see some of fingerprints of this enormous jökulhlaup (including Kötlubjarg (below) and large levee-formations..


Kötlubjarg, a large boulder carried by the jökulhlaup of 1981. Mżrdalsjökull and Katla in the background. Photo: Ólafur Ingólfsson, 2004.

Key sites on the way to Skaftafell National Park include Kirkjubęjarklaustur, where we will see some beautiful columnar lavas, and the great Eldhraun lava. It was produced in 1783 by an enormous eruption along the Laki crater row. In all, the lava covers about 599 km2, and is the most extensive lava field in the world resulting from a single eruption during historical times. The amount of eruptives (lava, pumice, ash, gases) has been estimated to be about 15 km3 during the 8 months of eruption. The volcanic pollution caused livestock to die, and there followed a famine that killed about 1/4th of the Icelandic population at the time. The pollution caused haze over most of northern Europe.

Pressing eastwards, we will enter the great Skeidarįrsandur, in front of Skeišarįrjökull. There we will have the opportunity to see some signs of the great jökulhlaup that occurred in connection with an eruption in Grķmsvötn, in Vatnajökull, in 1996. When we enter the Skaftafell National Park, we can choose to visit either of two outlet glaciers that terminate in the park, Skaftafellsjökull or Svķnafellsjökull.


Svķnafelljökull in the Skaftafell National Park. Photo: Ó. Ingólfsson, 2005.

We vill also visit Svķnafellslögin, a sediment sequence in the root of the great Öręfajökull volcano. It is about 700 ka old, and contains fossils (primarily leaves) that tell a story about the ever increasing harschness of the climate on Iceland through Pleistocene. Here, elements of the decidious broad-leave forest that characterized the Tertiary flora of Iceland occur for the last time in Icelands geological history.

Alternatively, we will visit Breidamerkurlón, the glacial lake in front of Breišamerkurjökuill, and make a stop at the large neoglacial/Little Ice Age moraines at Kvķįrjökull.

Öręfajökull is the largest active post-glacial volcano in Iceland. Its north-western rim is Hvannadalshnukur,the highest peak in Iceland. Its crater is 5 km wide and it has a rim averaging 1,850 m high.   Öręfajökull has erupted twice in historical times, in 1362 and again in 1727. The 1362 eruption was explosive and in regards to the amount of tephra produced, was the largest in Icelandic historical time. This eruption completely destroyed the district of Herad with jökulhlaup floods and tephra fall. By the 1400's a new settlement had sprung up again in this area under the name of Öręfi meaning "wasteland" in Icelandic. In 1727 Oraefajokull erupted again explosively with similar affects, but the eruption was smaller than the one in 1362.
 

Saturday 11th of June. This will be the last day of the excursion. We will take a route across the lowlands of southern Iceland, and out to the south coast of the Reykjanes Peninsula. The day will be devoted to various volcanic landscape elements, rugged terraines of subglacial volcanism, explosion-craters, crater rows, rift-fissure systems etc. We plan to be back at the Youth Hostel in Reykjavķk by 17:00. End of the excursion.

Sunday 12th of June. Check out from Youth Hostel.

 

Pdf library, with papers on Iceland geology:

Geology and Geodynamics of Iceland

Maizels on Jökulhlaup

The 1996 eruption in Vatnajökull

The Heimaey Eruption 1972

Björck et al, Preboreal oscillation

Reykjanes Ridge rift tectonics

Jökulhlaups and floodplain development

Reykjanes Ridge fault tectonics

Iceland Hotspot discussion

Ingólfsson et al, Pleistocene-Holocene transition on Iceland

Jennings et al, deglaciation of the Iceland shelf

Kjęr and Krüger, dead-ice develoment

Knudsen et al, Lateglacial development off N Iceland

Rundgren and Ingólfsson, Plant survival over a glacial cycle

Björnsson, subglacial lakes and jökulhlaups

Erik Sturkell, Islands Geologi

 

Additional information and useful web links:

For knowing a little bit more about the Icelandic glaciers, click here

Information on Icelandic climate, click here

Everything you ever need to know about Iceland (and more), click here

Iceland volcanism and volcanoes

More on volcanoes

Hey, check this one out: The rock band Led Zeppelin was seriously influenced by their 1970 visit to Iceland

 

 

 


A geological map of Iceland, with a sense of topography. Source: http://www.union.edu/PUBLIC/GEODEPT/COURSES/petrology/labs/iceland/iceland.htm