From the Field

Fire-And-Iceland

FROM A GEOLOGIC LABORATORY, INSIGHTS INTO CULTURE

By Martin E. Ross

Iceland, one of the most active volcanic centers on earth and the only point where the Mid-Atlantic Ridge rises above the sea, also is partially covered by several spectacular ice caps. For these reasons, Iceland is an outstanding natural geologic laboratory, making it an easy selection as the topic for a joint Geology/Honors Program course I and three other faculty members taught last spring to twenty undergraduates. The culmination of the course was a two-week field trip through the wilds of Iceland this September.

Our main purpose was to extend the students' learning experiences beyond the classroom by providing the opportunity to observe Iceland's unique volcanic, tectonic, and glacial features and processes. Our second objective was to learn about Icelandic history and culture, which have been so thoroughly influenced by geologic processes since the country was settled in the tenth century. I was joined in this formidable undertaking by philosophy professor Mike Lipton, director of the Honors Program and the co-organizer and co-leader of the course, and by William Newman and Patrick Colgan of the Department of Geology. Two University of Iceland geologists also served as co-leaders of the field trip. A guest professor of philosophy from the University of Iceland, Mikael Karlsson, taught the cultural/historical component of the course and led the trip's final portion, when we visited historic sites.

I also wanted to visit Iceland to further my own research in ancient basaltic volcanism, especially lava flows and the dikes (linear fissure vents) from which they erupt. Iceland, consisting almost entirely of such rocks and experiencing continued volcanic activity, offers a spectacular vantage from which to derive models for ancient basaltic volcanic features and processes. One problem I have been investigating is the nature and origin of chemical trends across individual basaltic dikes located within the North American continental crust. The trends that I have documented could be caused by a combination of magmatic processes and/or contamination of the basaltic magmas (containing less than fifty-two percent silica) with continental crustal material (containing greater than sixty-five percent silica). Since Icelandic magmas have not penetrated continental crust, I hope to compare chemical trends across individual dikes there with continental dikes.

Our first night was spent in Reykjavík, the capital, where we were greeted by the rector of the University of Iceland at a reception in our honor. The next morning we drove north along the shores of two large fjords, Havalfjordur and Borgarifjordur, carved by glaciers into the Tertiary period lavas forming most of the western portion of the country. These lava flows began erupting sixteen million years ago at what was then the center of a much smaller island. Continuous intrusion of dikes and eruption of basalt lavas have subsequently shouldered aside these older rocks to make way for the newly forming oceanic crust, a process that continues to this day in central Iceland. This central "neovolcanic zone" of postglacial volcanism and tectonism marks the boundary between the North American and Eurasian plates. Those continents were once joined but are now separated by the width of the Atlantic Ocean, and are continuing to move apart at the rate of about two centimeters per year. The rise of basaltic magma through dikes all along the Mid-Atlantic Ridge helps power this process of seafloor spreading. Besides being located along this ridge, Iceland is also positioned over a plume of hot mantle rock and magma, producing a "hot spot" at the surface. This double volcanic whammy results in prodigious production of lava and is why Iceland is piled above sea level.

As we wound our way eastward through the countryside over the next several days, we encountered progressively younger lavas upon entering the western neovolcanic zone. At one point we hiked across a 1,000-year-old lava flow (a mere infant geologically) and climbed down into a lava tube the diameter of the Callahan Tunnel. We examined frozen lava drops and the traces of old lava surfaces on the walls of the tube. About an hour later, we climbed out through a large opening where the ceiling had collapsed. The students learned that such lavas are able to remain molten and advance over tens or even hundreds of kilometers by flowing in lava tubes where they are insulated from the cold air and underlying ground.

Appropriately, the heart of the Icelandic political and cultural heritage is located at Thingvellir, right on a rift in the western neovolcanic zone. The Althing, the oldest operating parliament on earth, has gathered here almost continually since its inception in 930. Grievances were settled and the laws were spoken, entirely from memory, at the Law Rock, a knob of basalt lava located on the wall of a large, open fissure. It is believed that this site was selected for its fine acoustics provided by the basalt forming the vertical walls of the chasm. The legislature, though now located in Reykjavík, still meets at Thingvellir on special occasions. At Thingvellir, our students were able to appreciate how cultural development is often closely dependent on geologic conditions and events, a common theme in Icelandic history.

Even more direct is the connection between the very fabric of the Icelandic economy and its geologic surroundings. Iceland is blessed with abundant hydroelectric power due to its multitude of fast-flowing glacial streams and spectacular waterfalls. It is further blessed with hydrothermal energy stored at shallow depths in rocks and groundwater that are heated by magma chambers beneath. We saw evidence of these subterranean hot-water systems throughout our travels in the form of hot springs and geysers, both of which are sources of much income from tourism, Iceland's second-largest industry after fishing. At present, the nation is at a major crossroads, deciding between inviting in more power- and water-dependent heavy industries or shipping energy to Europe via yet-to-be-built cables on the ocean floor. Increased industry could mean less tourism if not controlled properly, and the idea of selling energy to European factories has much appeal.

By the eighth day of our trip, we had progressed to the moss-covered 1783 Laki basalt, the largest lava flow on the planet in recent history. In addition to burying many farms under lava, the eruption released tremendous volumes of poisonous gases (mostly sulfur dioxide) into the atmosphere and onto the soils. A bluish cloud of sulfuric acid droplets spread as far as Europe and western Asia. This event produced the Haze Famine of 1784 and 1785, during which twenty percent of Iceland's population and half of its livestock perished. Some Icelanders even speculate that the effects of the haze on crops in Europe contributed to political unrest and helped trigger the French Revolution.

We spent the next two days studying the remarkable ice caps in southeastern Iceland. Besides observing the deeply crevassed surfaces and the internal features of the glaciers, students saw firsthand the myriad deposits marking the prior extent of the ice. Once again the evidence of geologic impact on human activity was dramatic. We stood where, just a few months earlier, a subglacial volcanic eruption had produced a giant glacial outburst flood (jokulaup) which surged from Vatnajokull ice cap and tore a path of destruction across the sandy coastal plain that owes its existence to numerous prior jokulaups. The bridges have been rebuilt but the channels and deposits remain, pocked with kettle holes marking where numerous icebergs came to rest and melted on the outwash plain. At two places we were able to examine icebergs at close range. Over the centuries, these catastrophic floods have dictated the location of farms along much of the south coast of the country.

Soil erosion is occurring at an alarming rate throughout Iceland. This is due mainly to centuries of cutting forests for wood. The problem is compounded by the widespread grazing of sheep. Very little forest remains and current attempts at reforestation are losing ground, literally.

It is clear that this tour through one of earth's most amazing natural laboratories provided students with a unique and valuable learning experience. "My trip to Iceland showed me that there is more to academic life than just sitting in a class, that you can go out and discover things you once only read about," said David Velasco, a geology major. Dan Saulnier, a civil engineering major, told me, "The geology field trip was fantastic. All learning should be this fun."

Martin Ross is an associate professor of geology.