New Archeological Techniques Reveal 600-Year Old Marae In Cook Islands

Researchers use infra-red, thermal imaging to detect hidden structure

By Richard Moore

RAROTONGA, Cook Islands (Cook Islands News, Sept. 8, 2016) – A 600-year-old marae has been found on Rarotonga, without one spade full of soil being dug up.

Instead, researchers used ultra-modern technology to locate and map the structure in the hills behind the Highland Paradise centre.

They found the marae site and also dwellings and locations where there might have been houses.

The images also show a pathway and an opening, which could be a doorway.

The academics, from the University of Canterbury, used an infra-red or thermal imaging camera so they would not have to disturb the ground.

“We were wondering how we could use infra-red and multispectral imaging to detect archaeological structures because archaeology, in general, is very invasive and not all cultures want that kind of invasive technique,” said Ming Khan, a third-year student of Science and Earth Systems.

 “We wanted to know whether photography could be used to do something that was completely non-invasive.

“So it doesn’t hurt any cultural ideas but, at the same time, we get to learn about the history of the people and this benefits everybody.”

The researchers knew it was important to map the site, while respecting people’s beliefs and cultures.

“So this is one of those ways we could do that,” she said.

Alice Oline rigged a camera up in a tree overlooking the site and had it running for seven hours from mid-afternoon to 9pm.

It took an infra-red photograph every 10 minutes so the scientists could observe how the rocks in the area changed their heat retention over a lengthy period.

And going from the afternoon to evening allowed them to monitor the reduction in heat.

As Oline said: “That’s when sun goes down and it’s cooling down as the sun sets and it’s getting dark.”

Ming said a shot every 10 minutes was ideal, because “it’s is a good enough time interval so we don’t get overwhelmed with data and we don’t have too little information.

“It’s a nice compromise.”

Khan said they believed the site was around 600 years old.

“A marae, here in the Cook Islands, is considered a sacred site and it can be used for many different purposes.

“We also found dwellings and possibly locations where there might have been houses.

“We can’t say for sure where the houses might have exactly been, but there are locations where there may have been one –seems to be a pathway and an opening, and that’s some pretty cool stuff.”

Associate Professor of Earth Sciences Travis Horton said: “The thermal imaging showed that the different rocks had different thermal properties.

“So we were able to pick out coral, from a rusty-looking basalt, to a fresher basalt, versus sandstone.

“This type of photography can be a non-invasive way to look at the structures and what sorts of stones were used in the building.”

And, Khan said, the technology is totally transferable to anywhere in the world and can be used across a variety of environments.

“People have used infra-red technology in Arab regions, in Yemen, in Mayan rainforest areas and also India. Now we can do it in the Cook Islands too.”

Horton said his group got “incredible” assistance from Makiuti Tongia and Teuira Pirangi at Highland Paradise.

“Makiuti understands the stories behind the stones.”

And now the scientists are discovering more stories about Cook Islands’ history through thermal photographs.

Cook Islands News
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