how archaeologists found the lost medieval … the rock used to build some of the temples of angkor....

How archaeologists found the lost medieval megacity of Angkor... http://arstechnica.com/science/2016/07/how-archaeologists-foun...

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waterworks for flood runoff and water storage had been reduced to pits and troughs in the Earth. It was practically impossible to identify a medieval Angkorian

house deep within the jungle.

All that changed when airborne LiDAR (for "Light Imaging, Detection, And Ranging") came into common use for mapping in the early 2000s. Archaeologists

working in Cambodia immediately seized on it. By scattering light off the surface of the planet, LiDAR systems can produce maps with accuracy down to the

centimeter even if the ground is covered in heavy vegetation. The system is ideal for a place like Angkor, where the city's remains are cloaked in vegetation and

characterized almost entirely by elevated or depressed plots of ground.

With funding from the National Geographic Society and European Research council, archaeologist Damian Evans and his colleagues conducted broad LiDAR

surveys of Angkor in 2012 and 2015. The team's mapping rig consisted of a Leica ALS70 HP LiDAR instrument mounted in a pod attached to the right skid of a

Eurocopter AS350 B2 helicopter alongside a 60 megapixel Leica RCD30 camera. It was as if an invisible city suddenly appeared where only overgrowth and

farmland existed before. For the first time in centuries, people could discern Angkor's original urban grid. And what they saw changed our understanding of

global history.

Archaeological researcher Piphal Heng, who studies Cambodian settlement history, told Ars that the LiDAR maps peeled back the forest canopy to reveal

meticulous grids of highways and low-density neighborhoods of thousands of houses and pools of water. There was "a complex urban grid system that

extended outside the walls of Angkor Thom and other large temple complexes such as Angkor Wat, Preah Khan, and Ta Prohm," he said. With the new data,

scientists had solid evidence that the city of Angkor sprawled over an area of at least 40 to 50 square km. It was home to almost a million people. The scattered,

moated complexes like Angkor Wat and Angkor Thom were merely the most enduring features of what we now know was the biggest city on Earth during the

12th and 13th centuries.

From legend to reality

The city of Angkor has its origins in the ninth century during the reign of Jayavarman II. He unified large parts of Southeast Asia by establishing the Khmer

Empire across regions we know today as Cambodia, Thailand, Vietnam, and Laos. Inscriptions on temple walls at Sadok Kok Thom in Thailand describe how he

established a city called Hariharalaya, located near Siem Reap in the Angkor area. But the inscriptions also say that Jayavarman II declared himself a supreme

ruler or "god-king" in a lavish Hindu ceremony held at his residence on Kulen Mountain in a city called Mahendraparvata. Accounts of the Kulen Mountain phase

in Jayavarman's life are so sparse and fantastical that debates have raged among scholars about whether he actually lived in Mahendraparvata at all.

To find out more, archaeologists targeted Kulen Mountain in their latest LiDAR survey. Last month, Evans published some of the first results from this 2015

survey in the Journal of Archaeological Science. Royal Academy of Cambodia archaeologist Kaseka Phon explained to Ars via e-mail that the LiDAR has uncovered

an Angkor-like city grid at the abandoned city of Mahendraparvata on Kulen Mountain. Plus, the LiDAR "shows not only features of the construction, but also

water features" that are clearly versions of Angkor's incredible water management facilities. The new survey revealed massive stone quarries, now filled in, that

produced the rock used to build some of the temples of Angkor. Kulen Mountain's role in the birth of the Khmer Empire is no longer a legend—it's an

established historical fact.

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Charles J Sharp

This aerial photo shows what Angkor Wat looks like today, surrounded by vegetation and a few areas of modern farms and homes.

None of the vast city grid from 800 years ago is visible.

In the LiDAR map, you can clearly see the central urban grid of Angkor exte

(bottom left).


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JUMP TO END PAGE 1 OF 2

ns and reports written

by Chinese travelers who visited the city during the 12th century reign of King Suryavarman II, who built Angkor Wat. But historical sources are often

exaggerated or incomplete. Plus, it was difficult for Western researchers to believe that the Khmer Empire's great city was home to almost a million people,

dwarfing European cities of the same era. Now, such facts are impossible to deny.

Angkor city planning

Angkor reached megacity proportions in the 12th century, when Suryavarman II ordered the construction of Angkor Wat (which he dedicated to the Hindu god

Vishnu). At that time, the urban sprawl in Angkor was not only enormous, but it was centrally planned with rigorous precision. Heng told Ars that "the shape of

roads, walls, moats, mounds, and ponds were probably made based on urban templates commissioned by the Angkorian rulers" while residents of different

neighborhoods probably had different degrees of freedom to modify those plans. Heng continued:

To learn more about everyday life in Angkor Wat, University of Illinois Urbana-Champaign archaeologist Alison Carter has done excavation work on some of the

residential mounds inside the enclosure. In 2015, she got funding from the National Geographic Society to excavate one of the residential mounds identified via

LiDAR. Carter discovered what appears to be the remains of a brick stove, complete with ceramic vessels for cooking. Chemical analysis revealed remains of

pomelo fruit rind, seeds from a relative of the ginger plant, and grains of rice. This is what archaeologists call "ground truthing," and it's further confirmation that

the mounds we see in LiDAR are actually from households rather than other structures.

The picture that's emerging of Angkor is much like a modern low-density city with mixed use residential and farm areas. As Evans put it to Ars, "in the densely

inhabited downtown core there are no fields, but that nice, formally planned city center gradually gives way to an extended agro-urban hinterland where

neighborhoods are intermingled with rice-growing areas, and there is no clear distinction between what is 'urban' or 'rural'." The city was a miracle of

geoengineering with every acre transformed by human hands, whether for agriculture or architecture.

Perhaps Angkor's greatest technological achievement was its sophisticated waterworks, including artificial canals and reservoirs. People strolling through the city

800 years ago would have passed through neighborhoods whose carefully arranged homes were built alongside rainfall ponds for families, as well as enormous

canals for the city as a whole. Massive rectangular reservoirs held water all year around for agricultural use.

Each neighborhood would have looked slightly different, though all relied on the same water infrastructure. The city had to survive the floods of the rainy season

and slake the thirst of people and farms in the dry season. For centuries, it accomplished this incredible feat, which modern cities still struggle with.

Suryavarman II ruled a city whose mythic proportions were enabled by the most sophisticated engineering techniques of his day.

At temples such as Angkor Wat and Ta Prohm, the grid usage was significantly varied. For example, based on our recent excavations, after the urban

grid was laid out, there is little evidence of modification—if at all—in a series of habitation mounds inside Angkor Wat. While for Ta Prohm, its

inhabitants seem to have more freedom in modifying parts of their gridded mounds.

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Damian Evans / Journal of Archaeological Science

Comparison of major temple complexes in the 12th to 13th centuries, all at the same scale. Later developments (right column) show

more variable grids than earlier ones (left column), with areas within the moat divided neatly into ~100x100 m "city blocks." 6a:

Angkor Wat. 6b: Beng Mealea. 6c: Preah Khan of Kompong Svay. 6d: Preah Khan of Angkor. 6e: Ta Prohm. 6f: Banteay Chhmar.

"Mound fields" across Cambodia. Panels a,b are in the Phnom Kulen area. P

complex at Sambor Prei Kuk. Panels e,f are Immediately to the west of Bant

East Baray reservoir at Angkor, new archaeological mapping (3g) based on t

grid of mounds (3h) and revealed a second mound field to the south of the

acquired in the 2015 campaign. Panel 3g is based on archaeological maps b


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ANNALEE NEWITZ

Annalee Newitz is the Tech Culture Editor at Ars Technica. She is also the author of Scatter, Adapt, and Remember: How Humans Will Survive a Mass Extinction, and her first novel willbe published in 2017.

EMAIL [email protected] // TWITTER @annaleen

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Mysterious coils and mounds

Plenty of unknowns remain at Angkor, and the LiDAR surveys have revealed two previously unseen structures that nobody has been able to explain so far. The

first is a complicated rectangular maze pattern dubbed the "coils," "spirals," or "geoglyphs." These were first spotted outside the moat at Angkor Wat during the

2012 survey, but the 2015 survey revealed similar coils outside the enclosures at Beng Mealea and Preah Khan. At first glance they appear to be waterworks, but

Evans and his colleagues dismissed that idea because they are too shallow and are cut off from the city's general waterworks.

Currently, the reigning hypothesis is that these rectilinear coils were specialized gardens for growing plants used in temple rituals. The often-flooded channels

might have contained lotus, while the raised areas could have supported "aromatics such as sandalwood trees."

More mysterious are the so-called "mound fields" found near some of Angkor's largest reservoirs and canals. Unlike the residential mounds excavated by Carter

and her colleagues, these mounds aren't packed with ceramics and food remains. They are just mounds, clearly the foundations for an elevated structure or

structures. Their locations suggest that they may have been related to the city's waterworks, but of course correlation does not equal causation. Further

research is needed to unlock the secrets of the coils and mound fields.

Abandonment

One of the most intriguing questions about Angkor is why this once-incredible megacity is now inhabited mostly by trees and small, scattered farms. According

to many archaeologists Ars spoke with, that mystery has been largely resolved by the LiDAR data. First of all, said Evans, we have to let go of the idea that the city

was abruptly abandoned by hundreds of thousands of people at once. As he put it in an e-mail:

What the LiDAR reveals is that there were no mass migrations from Angkor to other areas. We don't see enormous urban grids springing into existence near

Angkor after the 15th century. Instead, as Heng says, "collapse of a civilization is a long-term process, and it did not happen abruptly." Heng adds that many

parts of the city were never abandoned at all, though the gridded regions outside Angkor Wat's enclosure slowly emptied out after the 15th century. "Angkor Wat

has never been abandoned," he said. "The temple was still functioning when the French explorers came to visit, and it is still functioning today."

Invasion didn't drive hundreds of thousands of people away instantly. Evans suspects that poor water management and urban planning were ultimately the

culprits. In an interview with Next City, he said, "In medieval Angkor, for instance, the standard response to the failure of one part of the water management

system was not to do things differently, but rather, to re-engineer the same thing in a different location, only larger."

So after decades of mystery, Angkor's abandonment proved to be more complicated than archaeologists thought—the story isn't of dramatic demise, nor a

sudden reversal of fortune. Angkor's slow decline was caused by the types of urban problems that still plague our cities today. It simply required a helicopter-

mounted laser to find out.

The standard narrative of the so-called "collapse of Angkor" was that there was an invasion by the Siamese in 1431 which basically laid waste to Angkor

in 1431, and that the kings and their populations moved en masse to capitals near what's now Phnom Penh. [The LiDAR data shows] that the cities that

came after Angkor were actually very sparsely inhabited... which either means that (a) this great diaspora from Angkor didn't happen and that Angkor

endured a relatively prolonged demographic decline (rather than a sudden "collapse") or that (b) people migrated elsewhere (which I doubt).

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how archaeologists found the lost medieval … the rock used to build some of the temples of angkor....

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