Medieval ship found in Norway's biggest lake

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Resting at the bottom of Mjøsa, the largest lake in Norway, a shipwreck from hundreds of years ago is in almost perfect condition, frozen in time.

The vessel, with its unique stem posts and overlapped planks, reveals a moment in the lake's maritime history and is estimated to date between the 1300s and 1800s.

Researchers discovered the wreck during the execution of the Mission Mjøsa project, which aims to map the 140-square-mile (363-square-kilometer) lake bed using high-resolution sonar technology.

The Norwegian Defence Research Establishment led the mission two years after performing several remotely operated vehicle, or ROV, inspections of areas of the lake where large amounts of munitions had been dumped. The lake is a source of drinking water for about 100,000 people in Norway, according to the Norwegian University of Science and Technology, so the munitions posed health risks. The shipwreck was spotted during the survey of the lake.

"My expectation was that there could also be shipwrecks discovered while we were mapping dumped munitions — that turned out to be the case," said Øyvind Ødegård, a senior researcher in marine archaeology at the Norwegian University of Science and Technology and the mission's principal investigator. "It was just purely that the statistical chance of finding shipwrecks that were well preserved was considered to be fairly high."

The recently uncovered shipwreck is located at a depth of about 1,350 feet (411 meters) and was captured in sonar imagery, a system that uses sound pulses to detect and measure the area below the water's surface. The imagery revealed the ship measured 33 feet (10 meters) long.

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The freshwater environment and lack of wave activity at that depth had kept the vessel in pristine condition, except for corrosion of a few iron nails at each end of the ship. To Ødegård, the wearing away of the metal is a clear indication that the wreck has rested on the lake bed for quite some time, since corrosion would take hundreds of years to occur. Eventually, the ship may lose its structure when all of the nails disintegrate, he said.

In the stern section of the vessel, there are indications that there is a central rudder, a feature used for steering, which typically appeared no earlier than the late 13th century. Combining those two features, archaeologists were able to estimate the ship's construction as occurring no earlier than 1300 and no later than 1850.

The ship appears to have been built using a Norse technique, in which the planks of the body are overlapped with one another. This method was used during the Viking Age as a way to make the vessel lighter and stronger and is known as clinker construction.

Since the shipwreck was found in the middle of the lake, Ødegård believed the ship had gone down in bad weather. It's most likely that the ship used square-shaped sails, he added, that proved to be difficult to navigate for seafarers caught in extremely windy conditions.

The oldest vessel to be discovered in Norway's waters to date is the Sørum logboat, found in the Bingen Booms on the Glomma River and dated back to 170 BC. The nearly 2,200-year-old shipwreck was relatively well preserved for being thousands of years old.

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"Wooden shipwrecks can be very well preserved in freshwater, since they lack the organisms that usually eat wood that are found, for instance, in the ocean," Ødegård said. "I assume that if we are going to find intact Iron Age or medieval vehicles in Norway, then (Lake Mjøsa) would be the place to look, since it's big enough to have had its own distinct maritime history with a lot of seafaring and trade."

During the Viking Age, the lake served as a big trade route, although there are notable gaps in what is known before and during these times, according to Ødegård. "No matter what the age, any find will help us to understand better how the development in shipbuilding tradition was like in an inland lake, as compared to the Nordic countries."

To map the bottom of the lake, the research team used a state-of-the-art autonomous underwater vehicle named Hugin, from Norwegian technology company Kongsberg Maritime. This is the first time such equipment has been used in a freshwater environment, according to Ødegård, and it has not been used much in archaeology. He called Hugin's research application for this occasion a "rare treat."

On the final day of the exploration, the researchers had sent down an ROV in an attempt to capture footage of the wreck, but they had to abort the mission due to bad weather. Ødegård aims to return next year to try again.

Meanwhile, the researchers continue to map out the bottom of the lake. To date, they have only mapped 15 square miles (39 square kilometers) and have much more to go. Ødegård said he anticipated more shipwrecks would be discovered.

"We could find vessels from since the beginning of human activity in the area. They could be present, and in good condition," Ødegård said. "You can't rule out anything."