A mysterious set of standing stones in southwest England, lost since the 1990s, will remain missing a little longer. But thanks to the search for them, archaeologists have new data about the ancient landscape on which the stones were built, which may shed light on the culture that left them behind.

Sometime between 4,500 and 3,000 years ago, people living in southwest England near present-day Devon carefully arranged 18 small pieces of sandstone—each about a foot high and nine inches wide—in two parallel rows. The rows were 113 feet long, with six feet of space between the stones. Their ancient builders settled each stone into a carefully dug pit, and the stones stood for thousands of years on Isley Marsh, a low-lying stretch of land near the sea. But now no one has seen the stones in over 20 years.

The disappearing stones

A power station was built near the stones in the 20th century. Its construction had changed the flow of water and sediment through the Taw Estuary and Isley Marsh, but its operations helped keep the Taw Estuary's channel relatively clear of silt. When the power station shut down in the 1980s, the silt began flowing into the marsh with each incoming tide, slowly burying the ancient standing stones.

“The power-station closure resulting in less discharge into the sea and less lively current, allowing sediments to settle, is one suggested cause,” Charlotte Russell, a project officer at Heritage England, told Ars Technica. She added that other factors, like silting up of the estuary in the absence of shipping, changes to railway and flood-bank construction in the area, and changes in runoff from upstream may all have played a role. The stones began to disappear.

“Some people that I work with here in Lampeter used to take field trips down to the estuary to look at these stones in the early 1980s and early 1990s,” geoarchaeologist Martin Bates told Ars. “I’ve seen some of their photographs, so they were already being buried by the late 1980s, and only the larger stones were still visible in the early 1990s.” By the mid-1990s, the stones were buried, and today archaeologists estimate that they’re covered by about a foot of silt.

Conservation organization Historic England wanted to know if the stones were still down there—and what condition they were in. The site is protected as a “scheduled monument” in the UK, and that status depends, in part, on the stones still being intact. Over the last 20 years, storms, the construction of nearby flood banks, and other landscape-management activities could have damaged or disturbed the stones.

“It is even possible that military maneuvers could have done so, as the site is very close to military practice grounds where water-based, amphibious, and landing-craft and troop movements are all carried out,” Russell told Ars. “Since the [scheduled-monument] designation, they avoid the area. But prior to that, there may have been more activity.”

“Much of the importance of the designation resides in the level of survival and archaeological potential of any site. Potentially, if a site has been destroyed and proven to be so, it would be de-scheduled,” explained Russell. “If it is actively being damaged it may be recorded more fully [and] possibly excavated to ensure preservation by record. We would hope at least, then, to recover any archaeological information before the site was lost.”

But for the moment, archaeologists aren’t sure what kind of shape the stones are in—because the stones are turning out to be hard to find. A team led Bates (who’s at the University of Wales Trinity St. David) spent a few days in the field earlier this week without much luck, and now the team is back in the lab, poring over data and considering what to do next.

You can’t always get what you want

“Well, we haven’t managed to find the stone row,” Bates told Ars. “It's going to take some more processing of the data, thinking about it, and doing some lab work on the sediments to more thoroughly understand the geophysics. And then probably [archaeologists would need] to go back, maybe, to have another go at it.”

The archaeologists were searching for the stones with an electromagnetic survey, which uses differences in how materials conduct electricity to spot buried structures or artifacts. At Isley Marsh, they expected fine sediments laden with salt water to conduct electricity much more efficiently than chunks of sandstone, which should make the stones stand out against the background of marsh sediment. But the stones are sitting amid a layer of loose gravel, which includes large pieces almost the same size as the Yelland stones and which conduct electricity in much the same way.

“When we were doing the geophysics, [we] picked up a number of anomalies which might have been the stones, but they have proved, in the test pits that we’ve dug, to be spreads of natural gravel,” Bates told Ars. It’s much too early to tell how—or even if—the stones’ protected status will be impacted.

And it’s not clear whether Bates and his team will get to do another survey. There are no plans so far, and Isley Marsh is an ecological preserve, so archaeologists have to time their work carefully—not only to catch the lowest tides of the year to avoid being flooded out mid-dig, but also to avoid disturbing the local and migratory wading birds that call the marsh home. For the foreseeable future, the Yelland stones look like they will remain lost to time.

“You know, there's still a chance we're going to find it, but it’s pretty difficult going out there,” said Bates.

But even if archaeologists can’t put a finger on the stones at the moment, they’re safer beneath a foot of silt than exposed at the surface.

“Sandstone is potentially vulnerable to wetting and drying, which you get all the time in an intertidal zone when they're exposed,” explained Bates. “If you bury them in these sediments, they're going to stay wet all the time, and they're going to be protected from continual abrasion by gravel.”

Reconstructing an ancient landscape

And the sediment itself holds clues about the landscape on which the Yelland stones once stood. Researchers will analyze sediment samples from the test pits for traces of pollen and microfossils that might yield clues as to whether the stones were built in an intertidal marsh, a wooded area, or on farmland. They’ll also look at the structure of the sediment itself to understand the environment in which the sediment was deposited. The team will spend the next several months trying to tease out some answers for a report to be published later this year.

“The samples may confirm the setting and environment during the period of construction, which would help us map landscape and climate changes and may throw some light onto the living conditions of the population that constructed the monument,” Russell told Ars.

We don’t know for sure what Isley Marsh looked like 3,000 years ago, but Bates says the stones probably stood in the intertidal zone of the Taw Estuary even then, since England’s sea levels had reached their modern heights by 6,500 years ago. If that’s the case, then the ancient people of southwest England built these rows of stones in a place that would be covered by the sea twice a day, which makes the Yelland stones an unusual site.

“Most of our intertidal archaeology from this time period that we have around the British coast is there not because we built under those conditions, but the sea has flooded in after it’s been built and perhaps abandoned, because of changes in coastal geography and things like that,” Bates told Ars. And the Yelland Stone Row builders must have had a reason for that choice.

“I think the fact that it’s built in what I believe is an intertidal context must mean that people obviously had a relationship with the sea,” said Bates. “Maybe it was leading to the sea, maybe it was leading from the sea. [It’s] hard to say, but it opens a new window on these people’s lives: the fact that they are doing—for want of a better word, and I am not very keen on this word—ceremonial actvities in intertidal zones.”

Big questions remain unanswered

Of course, we may never know exactly what those activities were or what their significance was to the people who lived here during the Bronze Age. And we also don’t know—and may never—what else is down there beneath the silt and gravel of the marsh. Excavations in the 1930s found evidence of flint tools and other signs of occupation dating back to the Mesolithic period and stretching through the early Bronze Age near the site, but Bates says there’s less than he would have expected.

“Now, the question we’ve got to ask ourselves is ‘does that material exist, or has it been lost by erosion, or was it never at all?’” Bates told Ars. “Because obviously if it was never there at all, that’s very interesting, having an isolated stone structure like this in the middle of an intertidal zone.” He added that archaeologists in the 1930s, without modern survey methods, could simply have missed something.

Such artifacts, if they’re there and if they could ever be found, might shed some light on how ancient people used the stone rows. But Bates says there’s more to be learned from zooming out to look at the big picture: how the stones fit into the wider landscape, especially the two or three kilometers around the site. For instance, there’s a similar row of stones not far away at Oxmoor, which would have been visible from Yelland rows on a clear day, but archaeologists aren’t yet sure how or if the two sites are related.

“One of the big problems we have in both trying to understand what a site like this means, and indeed find it, is that we really need to understand the landscape it’s sitting in,” said Bates. “To really begin to get to grips with this site, we need to zoom out to a bigger scale and look at the site in its landscape context.” But for now, the answers, like the stones themselves, remain hidden in that very landscape.