Original Article Published on WashingtonPost.com
Cities buried beneath the jungle ground — it sounds like something out of an Indiana Jones film.
Yet Australian archaeologist Damian Evans has spent the past several years searching for them in the dense jungle land near Angkor Wat in Cambodia. During a phone interview early Monday morning, Evans told The Washington Post he and his team have mapped out more than 734 square miles of land, including “basically every modern temple complex in the entire country to some degree.” The findings offer new insight not only into the Khmer Empire, which reigned in what is now called Cambodia from around the 9th to the 15th centuries, but into the populations that lived in the area long before then.
Most dramatic among the findings is an entire medieval city for which Evans and his team had searched for almost 10 years before concluding it didn’t exist.
Evans also said this mapping proves, maybe for the first time, that human beings have terraformed the earth by diverting rivers and cutting down forests for thousands of years, since well before we had written records.
“The broad conclusion to draw from this is that we’ve underestimated how much humans have shaped their environments,” Evans said.
They’ll be presenting the findings in a paper set for release in the Journal of Archaeological Science and in a presentation Monday at the Royal Geographic Society in London.
The technology that made this possible would have made Indiana Jones’s job a lot easier, albeit less swashbuckling. Previously, archaeologists would have been forced to do this sort of topological mapping on foot, a slow and burdensome process, particularly in dense jungles like those of Cambodia. But advancements made in lidar — which stands for light detection and ranging — have made it possible to perform this sort of research from the air.
The technology was actually created in the 1960s, just after the laser was invented. It works a little like radar, which uses radio waves to find foreign objects. To put it simplistically, if a wave bounces back, then you know something is there. Lidar does the same, only it uses pulses of light, or lasers, to detect objects. It’s the same technology police use when hunting down speeding cars on the interstate.
But at its inception, lidar could only shoot about 2,000 pulses per second, which rendered it fairly useless for the sort of work Evans and his team do. At those levels, most of the pulses would merely bounce off treetops and the dense blanket of leaves under them, offering little to no insight as to what lay below. Modern lidar, though, can fire up to 600,000 shots per second. At that rate, enough lasers make it through the vegetation to offer information on what is underneath.