Ancient, buried footpaths visible using satellite instruments but invisible on the ground to the human eye will be studied in Costa Rica this summer after a 20-year hiatus by University of Colorado at Boulder and NASA archaeologists.
Images of the footpaths, some dating to 2,500 years ago, were first made in 1984 by a NASA aircraft equipped with a suite of instruments that can “see” in the electromagnetic spectrum invisible to humans, said CU-Boulder anthropology Professor Payson Sheets. Sheets and NASA archaeologist Tom Sever, a CU-Boulder graduate, used the data to pinpoint the footpaths in the Arenal region of central Costa Rica.
The researchers have been able to date the ancient paths using stratigraphy gleaned from the Arenal volcano, which has erupted10 times in the last 4,000 years. Excavations of the footpaths, covered by as much as six feet of volcanic ash, sediment and vegetation, turned up floors of ancient houses, as well as stone tools and pottery.
Last year, a commercial satellite known as IKONOS, designed and built by Space Imaging of Denver, took images of the footpaths in the visual and infrared portions of the light spectrum. Because the buried footpaths seem to have more vegetation growing over them and a thicker matrix of plant roots beneath the soil, the infrared instrument on IKONOS picked up a unique spectroscopic “signature” that caused the paths to show up as thin red lines in the images.
“Remote sensing has been used to detect ancient Roman roads, large prehistoric roads around Chaco Canyon in New Mexico and Incan roads,” said Sheets. “But we had no idea it would be possible to image these little erosional footpaths. It is an exciting find with potential archaeological applications to other areas of the world.”
The two-year project is funded by a $103,000 grant from the National Science Foundation. NASA also purchased $20,000 worth of IKONOS images for the team.
Previous work by Sheets’ team indicates footpaths link an ancient cemetery to construction stone quarries and a spring. The team will use Global Positioning System equipment this season to pinpoint various archaeological anomalies.
“One of our primary goals is to better understand the activities at the cemetery,” said Sheets, who noted the ancient dead were placed in coffins made of stone hauled in from several miles away. In addition, funerary ceramics and cooking and food-serving vessels, as well as many whole and fractured cooking stones, indicate the people camped, cooked and feasted at the cemetery for extended periods.
“There seems to have been a supernatural component to their behavior,” he said. “The people likely saw the graveyard as an access to the spirits of their ancestors.”
A primary question the team hopes to answer is whether the cemetery was used by one or more villages, he said. If it was used by more than one village, then the feasting could have integrated different village societies by facilitating organized labor, inter-village marriages, surplus food production, new alliances and trade.
A newly identified footpath discovered with IKONOS leads perpendicular to the primary graveyard path and may indicate more than one village was involved in the feasting rituals, said Sheets. The team will spend two months in the Arenal region, following the footpaths that conceivably could lead to villages.
CU-Boulder doctoral students Derek Hamilton and Devon White and master’s candidate Errin Weller will accompany Sheets to the site. In addition, CU undergraduate Michelle Butler will be part of the excavation team as a result of funding through the NSF Research Experience for Undergraduates program.
Sever will be accompanied by NASA technician Dan Irwin. The team also will hire several local residents and involve Costa Rican archaeologists to assist in the project. The team will be in Costa Rica from about June 1 to Aug. 1.
The Costa Rican people established village life in the Arenal region about 4,000 years ago and maintained it up to the Spanish Conquest at about 1500, outlasting both the nearby Aztecs and Mayans “with a tremendous continuity of culture,” said Sheets. They apparently avoided the disastrous eruptions of the Arenal Volcano, returning after the events to farm corn and beans in the nutrient-rich volcanic soil.
“They inhabited a very large region and seemed to avoid conflict, conquest and serious disease,” Sheets said. “They appear to have led comfortable lives, relying on an abundance of natural resources and a stable culture.”
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