"Vikings Unearthed" in Iceland

One of the joys of writing my book The Far Traveler was joining an archaeological crew in northern Iceland for six weeks in 2005. There I worked with Doug Bolender, who is featured on the NOVA TV program "Vikings Unearthed" airing tonight (April 6, 2016) on PBS.

The summer I joined them, Doug and his colleague John Steinberg, both now at the University of Massachusetts-Boston, were testing a new protocol that has since proved to be a very powerful way to locate ancient structures buried beneath the soil--without having to dig. Their method centered on a ground-penetrating radar (GPR) device: a sealed plastic box full of electronics, which sent pulses of microwaves into the ground and picked up their echoes; these were then read by sophisticated computer algorithms and compiled into detailed maps of the density and other characteristics of the earth at certain depths. The archaeologists spent weeks dragging the GPR box over the ground above a suspected Viking Age house. My contribution was to hold one end of a 100-meter tape measure so they would walk in a straight line.

John Steinberg and team doing GPR in Iceland in 2005.

Paired with this high-tech gadget was a more primitive tool: a soil-corer, a steel T made of tubing, with a narrow opening the length of the shaft. But the method, as I learned one day, was just as precise and equally tedious.

Following a mental grid Doug had set over the field using GPS, we took a sample every 50 meters (165 feet) along a certain north-south line, then turned east and took another line. For each core, we chose a place between þúfur—the knee-high grassy hummocks caused by frost-heaving. Þúfur is one of the first Icelandic words you learn out on the farms. They make walking through an Icelandic pasture an obstacle course, taxing the ankles and straining the knees. Once I misstepped, my attention caught by a pretty palomino stallion in the next field, and fell full-length on top of a þúfa—it was like a belly-flop onto a medicine ball.

While I floundered, Doug had found a grid-point between two thufur and plucked away the grass. Once I’d found my feet, he handed me the coring tube with a flourish. Attempting to regain my dignity as well, I punched it through the turf and pulled out and discarded the root-plug, as he had instructed. Then I pushed the instrument straight down, stomping on the foot pedal, which, like usual, slipped from its groove, leaving me stomping air and jarring my back. Doug laughed and took over: He had a special wiggle that made the pedal work.

Archaeologist Doug Bolender working in Iceland in 2015.

When the corer was fully buried, he stepped aside again to let me redeem myself. “Don’t twist it,” he warned. I crouched, set my feet well under the handle, hooked my elbows under the cross-bar, and lifted up with my thighs, not my (already tender) back. The tube slowly slid from the earth, full of soil. Doug sliced his pocketknife across the narrow opening to reveal the strata of that 50-centimeter (20-inch) sample: layers of deep red, black, shiny white, then brown, rust-red, tan, and honey-yellow. Some of the strata had been swirled around, either by flooding or by what Doug called “cryoturbation”: freeze-thawing, the same process that makes the þúfur, which inspired one member of the team to rename it thufurization.

The core was beautiful. “You could make upholstery out of that one,” Doug said.

A sample soil core from the SCASS blog.

I took up the clipboard to log in the color and depth of each soil layer and measure the location of the volcanic tephra lines. The honey-yellow line near the bottom of the core was tephra from an eruption of Mount Hekla nearly 3,000 years ago. It marked prehistoric soil, telling us we’d drilled deep enough. The shiny white tephra was more interesting: the distinctive marker left by Hekla’s eruption in 1104. In between there should have been—but I couldn’t see it—a thin dark gray layer. This tephra has been dated, by comparing its chemistry to dust found in the Greenland ice cores, to 871 (plus or minus two years). The date is remarkably close to when Iceland’s first historian, Ari the Learned, says Iceland was settled: 874. Archaeologists call this tephra the Landnám or Settlement Layer. Another, lighter greenish-gray tephra—also, unfortunately, not visible in this core—dates to the year 1000. Layers from 1300 and 1766, likewise conveniently color-coded, can also be found in Skagafjord cores.

Tephra line in a turf wall in Iceland.

The volcanoes from which this tephra spewed are clear across Iceland, near the south coast. The wind direction during the eruption, and the ground cover where the tephra landed, determined if a core will have a tephra line or not: bushes and thick grass trapped tephra, while on bare gravel and rock it washed away. Skagafjord is a good spot for archaeologists because the wind generally did bring tephra from these historically important eruptions north.

Using this handy vulcanological dating method, if you take enough soil samples (and for his Ph.D. dissertation on medieval farming practices, Doug collected approximately 16,000), you can see a “massive jump” in phosphorous levels, due to animal manure, in farmers’ fields between 870 and 1100. You can also, if your grid is tight enough, find and date the farmers’ houses and garbage middens by the position in the soil cores of charcoal, bone, peat ash, or chunks of turf.

It's not an easy job to get 16,000 soil cores. There are surprising dangers.

One day, two members of our team, Susan and Tara, were coring in a fenced field. The farmer had told them it contained a herd of “calves.” One came over and pissed on the leather corer bag. The next day, it came up to them and let them scratch its nose. It stood beside them, grazing, while they recorded the last soil core.

Skagafjörður, Iceland, where we were coring.

When they were ready to leave, they decided it wasn’t a good idea to get between him and the rest of the herd, so they walked directly away from the "calf." He snorted and champed and charged after them, suddenly morphed into a raging bull. They ran, dodging thufur, clutching their instruments.

Up ahead Tara saw a drainage ditch—This way!—she leaped into the ditch and sank up to her thighs in muck. Susan followed. The bull tried to get under the fence and into the ditch. He went under head and shoulders. They dropped the corers on the bank and slogged up the ditch away from him until they could get up the bank and under the far fence.  Leaping up the bank out of the ditch, Tara cradled the $300 GPS monitor, Susan the soil-coring data sheet. They waited until the bull lost interest and went away before going back into the ditch to retrieve the rest of their equipment.

Watch the PBS special "Vikings Unearthed" online here: http://www.pbs.org/wgbh/nova/ancient/vikings-unearthed.html. For more on my book The Far Traveler, see my website at: https://www.nasw.org/users/nmb/books.html#FT. For more on Doug Bolender's work at UMass-Boston, see the blog of the Skagafjörður Church and Settlement Survey here: http://blogs.umb.edu/scass/2016/04/02/doug-bolender-stars-on-vikings-unearthed/.