Geologist Relies on GIS to Assist in Unraveling Complex Geology in Iceland
By Kevin P. Corbley

Skaftafell National Park in southeast Iceland may contain some of the most complex subglacially formed volcanic geology in that country-and possibly in the solar system. A geologist is unraveling the layers of volcanic eruptions and glaciation in the park with a combination of traditional field methods and GIS technology.
  Johann Helgason, president of Ekra Geological Consulting in Reykjavik, Iceland, began mapping the bedrock geology in the Hafrafell region of Skaftafell in 1987, primarily for the physical and scientific challenges it presented. The Iceland National Science Foundation eventually saw the value in having the geology interpreted at the popular park and provided three years of funding for the project.
      Since then, Helgason and an associate, Dr. Robert Duncan of Oregon State University in Corvalis, Ore., have made periodic trips to the rugged site to collect rock samples and traverse the lava formations. Over the years, they have accumulated thousands of pieces of data-GPS points, maps, sketches, samples, and images.
      With such a huge database to manage and manipulate Helgason turned to GIS technology in 1993, to assist in tracking the data and making sense of it. He considers the GIS software, TNTmips from MicroImages in Lincoln, Neb., to be effectively a black box into which he can deposit the disparate pieces of data, make his interpretations, and then produce an intelligible map on the output side.
      The geologic map of Skaftafell Park is scheduled for completion in Spring 2001. Helgason says production of the map would have taken much longer to accomplish due to the complexity of the rock formations and lithology if it weren't for the data storage, processing, and manipulation capabilities of the GIS software.

Geologic History Carved in Stone
Located about five hours by car from Reykjavik on the ring road that circles Iceland, Skaftafell has become a popular hiking and camping destination for families. The enormous Vatnajokull glacier, which flanks the park on three sides, and the Grimvotn and Oraefajokull volcanoes hidden beneath the ice, have together shaped the terrain that makes the park so intriguing to vacationers and geologists alike.
      In the last five million years, the processes of volcanism and glaciation have combined to write the area's natural history and preserve it in stone. Multiple eruptions triggered lava flows during alternating periods of ice coverage and non-glaciation, resulting in overlapping layers of lava rock with varying lithology and patterns of erosion.
      In this area, as in most of Iceland, rock layers typically alternate among three types of formations: lavas which flowed during ice-free eruptions, sediments which washed from beneath ice, and subglacial volcanics which resulted from eruptions under the ice. Each has a distinct appearance, making it possible to tell whether a formation dates from a glacial or an interglacial time.
      "We have recorded 18 different glacial phases in the past five million years, and 90 volcanic eruptions in the past 1.5 million years," said Helgason. "This makes deciphering the bedrock quite a challenge."
      Skaftafell also exhibits evidence of a rare geologic phenomenon called jokulhlaup, which occurs when volcanic eruptions take place beneath glacial ice. The heat of the eruption melts ice at the bottom of the ice sheet, and the meltwater remains trapped beneath the glacier. However, as the ice melts, the glacier begins to rise, eventually freeing the meltwater in a torrent.
      A major jokulhlaup event last occurred only four years ago in the park when an eruption broke out near Grimsvotn in the Vatnajokull ice sheet to the north. An estimated 55,000 cubic meters per second of melt water rushed from beneath the glacier into the park's lowlands, washing out all bridges and roads in its path.
     The jokulhlaup leaves behind a distinct pattern of sediment and erosion. Helgason mapped these features in Skaftafell and later identified similar morphology in NASA satellite images taken of the surface of Mars, lending further credibility to the theory that subglacial volcanism played a key role in forming parts of the Martian landscape.

Unraveling Formations with GIS
Ekra Geological Consulting is a small company that specializes in mapping bedrock geology in Iceland for clients planning and designing dam sites for hydroelectric power. This type of mapping is critical in these projects to ensure that no fissures exist in deep rock layers that might result in water seepage around and under the dams.
      Due to the size of his company, Helgason could not dedicate a staff position to that of an image-processing or GIS software specialist who could automate much of the mapping of Skaftafell and other projects. He reviewed commercially available packages based on user friendliness and their ability to run on a standard personal computer.
      "First and foremost, I am a geologist, not a computer specialist," said Helgason. "GIS is another geologic mapping tool that I wanted to use to my advantage, and so I chose TNTmips because it was easy for me to learn, and I could do everything I wanted with it."
      With so much data accumulating from the field work, Helgason obtained a topographic map to serve as his basemap. The map of southeast Iceland was created in 1951 by the U.S. military, which maintains a naval base on Iceland as a strategic position in the North Atlantic.
      Helgason scanned the map into TNTmips and then converted it to a vector file so he could use it as an overlay on other data sets. The software also enabled him to create three-dimensional views of the terrain based on the elevation data from the topographic map.
      Much of the geologic field work has involved walking traverses of the rugged Skaftafell landscape. In this process, the geologist walks in a straight line across an area of rock outcrops. He records the strike, dip and thickness of each formation, collecting samples if necessary to differentiate layers. This information is recorded and often sketched in a notebook.
      A few years into the project, Helgason obtained a GPS unit to record the positions of traverses and sample sites more accurately. When he returned from the field, he entered the GPS points into TNTmips. Rock samples were often sent to Oregon State University, where Dr. Duncan pinpointed their age using an Argon-Argon dating technique.
      In the field, formations were distinguished by their composition which, in many cases, was discernable to the naked eye. Helgason drew formation boundaries on aerial and ground photographs during field visits. A high percentage of the bedrock in the park is composed of one of three types of basalts characterized by grain size, and the presence or absence of crystals.
      Back in the office, Helgason drew stratigraphic profiles from his field notes and printed out portions of the terrain map with the points representing observation sites, traverse lines, and formation boundaries. Referring to his field notes, Helgason then connected boundary points for like formations exposed in different traverses, a complex version of connect-the-dots. Using this traditional geologic interpretation technique, he extrapolated layer positions throughout the project area.
      In instances where his field notes were incomplete, Helgason could manipulate the 3D view of the terrain in hopes that it would provide a clue to the sequence of formations and features. Often he would refer to a hardcopy aerial photograph of the region to fill gaps where the landscape had prohibited field visits.
      Helgason then scanned the geologic map into TNTmips and stored it as a raster file. As he built the map and added more information to it, Helgason displayed the topographic layer as an overlay on the geologic formations raster data. When new information enabled him to alter the interpretation, he used the CAD tools in the software to draw in the new formations, intrusive dikes, faults, and other features.

Applying Spatial Data to Park Management
When completed, the Skaftafell geologic map is expected to be used by staff members at the park as an information source they will rely upon in conveying geologic explanations to park visitors. With this in mind, Helgason is examining other spatial data sources to provide additional information for the final map.
      One of these data sources is a Landsat satellite image of the area acquired in July 1988, for the State Soil Reclamation in Iceland. Helgason imported the image into TNTmips and performed a supervised classification of the vegetation types in the park. Of special interest was growth in the park's lowland areas formed by outwash called sandur from the glaciers and jokulhlaups.
      "This region has gone through many phases of elevation and subsidence caused by fluctuations in glacial loading," said Helgason. "The increased load of inland ice elevates the coastal areas and vice versa, and the farmers are keen observers of such changes."
      He continued, "This has an impact on vegetation because when the land subsides, ground water is closer to the surface and the sandur plain supports more vigorous vegetation."
      Helgason plans to obtain another Landsat image to conduct a change detection between different dates to try and determine how vegetation was impacted by the great jokulhlaup of 1996. Such information could be valuable in deciding how to manage the land.
      "Soil erosion is a problem over most of Iceland, and the grazing of sheep on the vegetation contributes to the problem," he said. "If we find we can expect vegetation to increase in the fertile sandur area, then the farmers should be encouraged to graze the sheep there rather than in the more sensitive highland area where soil erosion is much more pronounced."

Preparing for Publication
The Skaftafell map was unveiled publicly for the first time in August 2000, at The Second International Conference on Mars Polar Science and Exploration conference held in Iceland. Helgason is putting the finishing touches on the legends, scale bars, and annotation for the final color version of the map, created entirely in TNTmips, for official release next spring.
      Use of GIS technology in creation of the geologic map makes it possible to store data in a digital format for use in other image processing and GIS systems. This ensures compatibility of the Skaftafell map with geologic mapping projects now underway in Iceland.

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