Richard Bates: “When is a pile of stones not just a pile of stones?”

The geophysicist and archaeologist on uncovering Petra’s secrets.

Two weeks after a tomb containing 12 skeletons was found in the ancient city of Petra, Jordan, this autumn, geophysicist Richard Bates was sitting in a gift shop-cum-café near the site. When Pearce Paul Creasman, director of the American Center of Research in Jordan, came across him, he asked: “‘What do you think?’ I’m, like, ‘Well, I haven’t been in yet.’ And he just looked at me a little bit funny. I says, ‘Yeah, I’m just having a coffee.’”

At this point, as far as Bates was concerned, the tomb that had been found was like the two previously excavated, adjacent chambers: empty but for a few scattered bones and grave goods. He was pleased his calculations of where to dig had proved correct, but he was in no rush to see a “hole in the ground”. “Eventually I said, ‘OK, go on then, let’s go down and have a look.’ And I went down and I got into it and I was, like, ‘You never told me any of this!’ It was quite astounding.” (Since the find was announced, it has been claimed the existence of the tomb was already known. Bates said he did not know this at the time of his work at the site.)

Petra, a World Heritage Site, was carved into the rose-gold sandstone walls of a wadi, or valley, by the Nabataean people around 2,000 years ago. It is an extraordinary, imposing settlement, incorporating elements of Greek and Roman architecture, including an amphitheatre, and, at its height, was home to 20,000 people. Little is known about the Nabataean people – largely because, aside from rock inscriptions, no Nabataean literature survives. They are believed to have originated as one of the nomadic tribes that roamed the Arabian Desert, emerging as a distinct civilisation in the fourth century BC. Petra developed as a permanent settlement owing to its position on the Middle Eastern trade routes. It was annexed by the Romans in AD 106, damaged in an earthquake 200 years later, and declined as trading routes shifted. Petra was largely abandoned by the middle of the seventh century, “lost” – at least to the West – until the Swiss explorer Johann Ludwig Burckhardt “rediscovered” it in the 1800s.

Today, Petra is an arid place, but the Nabataean people built a water conduit system to harness ground and rainwater, making the city a green oasis in the middle of the desert. At its centre was a complex of pools and exotic gardens. It was water that brought Bates to the site earlier this spring. “Petra is getting more and more extreme flooding going through it with climate change, extreme weather events,” he told me when we met in his office at the University of St Andrews one swiftly darkening afternoon in November. “Some of the tombs are absolutely rammed full of sediment debris” from flash floods. Bates was asked to begin surveying the site, as any future work to try to control flooding will have to avoid damage to buried structures.

The team’s work brought them close to the Treasury building, or Al-Khazneh, made famous as the resting place of the Holy Grail in Indiana Jones and the Last Crusade. It is not known when the Treasury was built (dating when rock was exposed, rather than formed, is difficult), though it is believed Petra’s most significant structures were erected during the reign of King Aretas IV, between roughly 9 BC and AD 40. The Treasury is thought to have been constructed as a tomb, possibly for Aretas. Its name derives from local lore that a carved urn on its facade contained treasures belonging to Aretas, or a pharaoh. In fact, the urn is solid rock.

Estimates of how much of Petra has been archaeologically explored vary between 1 and 20 per cent. Bates suspects he and his team were only granted access to the Treasury because of the impact of the Gaza war on tourism. “There were times in the plaza where there was two or three people – compared to normal when there’s hundreds, if not thousands, coming through,” he said. “At that point I did say, ‘Hey, what’s the chance of… getting in and doing something in the Treasury?’” To Bates’s surprise, they were granted the “incredible opportunity” to explore the structure, documented for the Discovery Channel series Expedition Unknown.

Bates used electromagnetic conductivity and ground-penetrating radar to survey the interior chambers of the Treasury and the shelf outside. The tomb they found was unusual not just for its burials: “Most Nabataean tombs… are just rock-cut floors… But this [tomb] has four dividers.” The skeletons have yet to be fully analysed, but are believed to be a mix of children and adults, and “the dating tends to suggest that it was fairly well confined within a 200-year time period at the middle of the Nabataean [age]”. Grave goods were also found, including what turned out to be part of a broken jug, but seemed at first a humble carpenter’s cup.

Bates was born in Aberystwyth, Wales, to a geologist father and a teacher mother. “I suppose you could say it was inevitable, as a family kind of thing, you go around and you’re kicking up fossils… that we went into geo- something,” he said. Bates’s brother is a professor of geoarchaeology in Wales. The two often work together, including on the Happisburgh footprints, the oldest footprints found outside Africa, which they discovered on a fast-eroding stretch of beach in Norfolk. “To stand there and just put your foot in them…” Bates marvelled. “And then two weeks later… they’re completely lost to the sea.”

Bates studied geology at Edinburgh, then did a PhD in geophysics in Bangor, Wales, before moving to the US to work for a consulting geophysics company. The work was multi-application – groundwater, mining, oil and gas, environmental, “the whole gambit of geophysics” – and Bates has continued a cross-disciplinary approach in his nearly three decades at St Andrews.

As well as archaeology (despite initially having no interest, his brother won him over), Bates applies geophysics to environmental study: “Stuff with ice and glaciers and climate change, and stuff with biologists on sea mammals, habitat mapping and ocean floors.” He has used 3D sonar to measure the size of whales. Bates sees geophysics as being like a toolbox. “When somebody has a problem, I stop and think, ‘I can try one of those and two of those and three of that, and we’ll see if that gives us something.’ This crap in here” – Bates gestured to the shelves of tools and boxes that line his office walls – “is part of that story.” Geophysics is ultimately, he told me, about looking for patterns and working out which are natural – “and nature can be pretty weird” – and which are “anthropogenic”: “What’s a pile of stones and what’s not a pile of stones?”

During Bates’s career, geoarchaeology has “progressed from being: use geophysics to help the archaeologists go from a needle in a haystack to a needle in a small handful of hay” – in other words, identifying where to dig – to having a role in preservation. “In a digital world, a remote-sensing world, it’s often now: how do we record something, tangible heritage, that is going to be lost from climate change… or destroyed in a war?” After seeing the destruction by Islamic State of part of Palmyra, Syria, in 2015, for instance, Bates worked with Bradford and Durham universities to render a 3D reconstruction from hundreds of crowd-sourced photographs.

Next year, Richard Bates hopes to travel to the Arctic, to survey sites associated with John Franklin’s lost expedition, to the Great Lakes in North America, and to Dwarka, India, where there is believed to be a drowned city. At Petra, much remains to be discovered. The true base of the wadi it inhabits is buried in sediment; what is visible today is only the beginning. “There’ll be a base to the wadi, and the electromagnetic geophysics shows you where that base is… the solid rock.” How far down might it go? “There’s probably another 20 metres down, so there’s a lot of room for things to be down there.”