Technology reveals ancient cultural secrets from beneath the jungle canopy

UNIVERSITY PARK, Pa. — As a grad student, Tim Murtha loved trekking through the rain forest deep in the heart of Mesoamerica. Backpack loaded with an assortment of survey equipment, he’d cut a swath through the brush, sensing adventure around each bend of the trail.

The excitement would mount as he began to notice clues in the moisture-laden forest around him. Seconds later, an ancient Mayan wall or stone edifice would come into view, draped in vines and barely decipherable in the cacophony of rainforest vegetation.

Though he’s a long way from the jungle today, Murtha says those breathtaking moments of discovery still happen to him as he sits with his students in his Penn State laboratory, peering at intricate software simulations and red, green and orange-hued 3-D maps on his desktop computer.

“Truth is, I’m a weird archaeologist,” he says, smiling broadly. “I love the material record, and I’m passionate about landscape archaeology — but I’m also a geek.”

Murtha’s choice of profession — an associate professor of landscape architecture who also happens to be an archaeologist — illustrates how mapping technologies have come to dominate the field of anthropology today. In fact, current archaeological excavation has become so technology infused, a modern-day Indiana Jones might need a laptop, smart phone, digital watch and high-performance cluster to beat the Nazis as well as he did 30 years ago in the classic adventure film "Raiders of the Lost Ark."

“The story of the rise and fall of ancient civilizations — how they lived, who they were, how they took care of their environment and how they interacted with others — is something we need to learn from to inform the modern practices of today. All these technologies are helping us see that picture in full detail.”

— Tim Murtha, associate professor

of landscape architecture

Murtha explains his passion for survey techniques in his field days led him to look more closely at the dynamics that brought about the rise and fall of the Maya through “the lens of the landscape they lived in” — and this approach helped him dive into the profusion of mapping technologies many archaeologists embrace today.

“Not only are these tools giving us incredibly detailed 3-D maps to investigate ancient cities, they help us look at settlement and ecological features such as erosion, farming, deforestation, water and soil,” he says. "But the amazing thing is how much technology is speeding up the interpretation process.”

With a conspiratorial nod, Murtha flips open his laptop. “Notice the color and the variation of smoothness and texture," he says, pointing to the glowing infrared relief on the page. "This tells us about the vegetation. And these clusters with the small white dots indicate Mayan ruins — probably walls," he explains. “Imagine if you were surveying or reconnoitering this area 20 or 30 years ago. You could be standing right next to these ancient walls, but with the profusion of vegetation in a tropical forest, you would never know it. It might take 50 years of painstaking grid-by-grid survey and excavation to find them.”

As the principal investigator of a recent multi-year National Science Foundation grant awarded to study 3,000 years of Mayan cultural evolution in Tikal National Park in Guatemala, Murtha says two remote sensing technologies are among the hottest commodities in archaeology today: NIR infrared and a system called lidar — a remote-sensing tool that combines laser, imaging, detection and ranging technologies.

NIR infrared involves satellite-generated infrared light using varying wavelengths to penetrate the Earth’s surface and search for objects. Murtha has been using images from NASA’s well-known landSAT satellite to create 3-D infrared-based maps of regions around the ancient city of Tikal by scanning for any man-made structures beneath the soil and patterns of vegetation that can’t be seen by the naked eye.

According to Penn State doctoral student Claire Ebert, the aerial technology lidar, on the other hand, may hold even higher promise for rainforest excavation because it enables scientists to see underneath thick, remote, tropical forest canopies, allowing them to find structures, temples and even whole cities no one ever knew were there.

A highly sensitive type of remote sensing technology, lidar uses lasers to create intricate relief data that can be examined in layers (something like peeling an onion). By mounting lidar systems on propeller planes or helicopters, archaeologists use the technology to uncover rainforest settlements and features that might have remained hidden from satellite imaging or ground surveys under the jungle canopy for decades.

“When I first saw the lidar for the region I had been studying, I was astonished,” Ebert says, “because it showed me there actually were large structures within a couple meters of the places where I had been doing excavations earlier. These structures had been totally invisible to me at the time.”

To help her understand the intricacies of Mayan society, Ebert has been studying how household histories evolve through time. “As craft and trade developed in the Maya lowlands, cities evolved and society became more and more stratified,” she says. “Based on the type of architecture and how artifacts changed through time, you can trace the development of societies from small villages with a few households to large centers with palaces and temples where kings and queens lived. We’re using lidar to track these settlement patterns.”

Ebert also uses other types of evidence to look at the development of complex society in the Maya lowlands, including large stone monuments with glyphic texts. These monuments provide one type of essential data because elite households inscribed them with dates and family histories.

Although he might have been stumped by technologies like lidar simulation or the nuances of interpreting infrared-generated 3-D maps, Indiana Jones would have no doubt loved some of the field gadgets available today. Ebert laughs, recalling a “laser-gun-from-Star-Wars”-like device (called a portable XRF) she and her colleagues used in the forest to analyze obsidian.

“You see, the volcanic glass obsidian was a highly valuable, everyday resource for the Maya, who made and traded tools with it — blades, spear points, arrows and scrapers — up and down the Mesoamerican coast,” she observes. “So we would use the XRF to reveal each obsidian artifact’s geochemical composition, pinpointing elements like rubidium, iron, copper and zinc. This helped us determine where obsidian had originally been mined and made it possible to map out the trade networks.”

Murtha, who also studies historic settlement patterns in Scotland, agrees that field gadgets can add to the excavation experience, recalling the fun of using pole-mounted cameras and kite photography to “fly” above a site and get an aerial shot without incurring the expensive costs of hiring a plane or helicopter.

“The story of the rise and fall of ancient civilizations — how they lived, who they were, how they took care of their environment and how they interacted with others — is something we need to learn from to inform the modern practices of today,” he says. “All these technologies are helping us see that picture in full detail. The whole combination of tools (both old and new) is bringing each piece of the archaeological puzzle together in a revolutionary way."

Murtha's fellow principal investigators for the National Science Foundation project are: Kirk French, lecturer in anthropology; David Webster, professor of anthropology; and Chris Duffy, professor of civil and environmental engineering.

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Last Updated May 21, 2014