One of the factors that contributed to so many geoglyphs being undetected prior to the aid of satallites is their enormous size. According to leading geoglyph scientist Alceu Ranzi, his latest discoveries--five sets of geometric shapes, with circles, squares and lines--can measure more than a mile from one extreme to another.

You do not see them in field. There is a difference in the color of grass but is very thin. If there were no satellite images, there would be no possibility [of making these new discoveries].

Because they've been so hard to find, the first geoglyphs weren't discovered until the 1970s. Since then, scientists have been trying to piece together what significance they may have had to ancient Amazonians. What ever the purpose may have been, there's one thing that is certain: the ancient civilizations of the rainforest were more numerous and sophisticated than previously imagined.

According to a report from Globo, the new marks were only discovered because the jungle coverage had been removed to due to deforestation in the Amazon. These structures are deep, with grooves are as large as 12 meters wide and four deep, but it is believed that they were built when jungle abounded--which would make their construction all the more difficult.

Ranzi seems open to other possibilities:

Was it really forest [when the drawings were built] or did they occupy this area at a time of climate crisis, like that of 2005?

The world may never know what drove these ancient civilizations to carve the enormous geoglyphs, like the ones found recently using Google Earth. But, if it takes more clear-cutting in the Amazon rainforest to find out the answer, hopefully it will always remain a mystery.

Also reported by Ogle Earth:

Out of Brazil, a remarkable story, as reported by Treehugger blog: The deforestation of the Amazon has provided one unforeseen boon to archaeologists — the denuded ground has laid bare some amazing pre-Columbian geoglyphs, visible from the air, and thus on Google Earth:

One of the factors that contributed to so many geoglyphs being undetected prior to the aid of satallites is their enormous size. According to leading geoglyph scientist Alceu Ranzi, his latest discoveries — five sets of geometric shapes, with circles, squares and lines — can measure more than a mile from one extreme to another.

Treehugger doesn't provide locations of examples of these geoglyphs, but Globo Amazonia does. For the sake of convenience, here they are on Google Maps — click here to see them on Google Earth.

View Amazon geoglyphs in a larger map