The method is well understood
One part of the Nazca story is not a mystery at all: how the designs were physically made. The evidence comes from the lines themselves, from tools and pottery found on the plain, and from experiments that have reproduced the process on a smaller scale. The answer is slow, labour-intensive, and entirely within the abilities of a farming society with ropes, wooden stakes and many hands. What is not known is why the work was undertaken.
Removing the dark stones
The desert surface is covered by stones, mostly reddish-brown to dark, whose outer layer has been darkened by exposure over a very long time. Beneath this layer the ground is paler, often yellowish-grey. To make a line or a figure, the makers cleared the stones from the intended path and piled them along its edges. The pale ground showed up as a contrasting groove or band.
This is why the designs are shallow. The grooves are normally only a matter of centimetres deep, and in some cases much less. The pile of removed stones along the edges is sometimes still visible and can help show where a line was made. The method was quick to carry out compared with digging, and it needed no complicated tools, though the work over long distances would have taken many people many days.
Setting out straight lines
Long straight lines are not difficult to lay out when one has stakes and cord. A common explanation is that a pair of people could keep a line straight by sighting along a row of stakes placed one after another, correcting the position of each as they went. Wooden stakes have been found at the ends of some lines and at points along them. The ground is flat, which helps.
Large figures present a different challenge. Researchers have suggested that the makers began from a smaller drawing and enlarged it by a simple proportional scheme, fixing a few key points on the ground with stakes and then linking them with cord to follow the outline. Experiments by researchers and writers who recreated a figure using replica tools and stakes showed that a small team could reproduce a large design with fairly good accuracy. Such trials show that the method is plausible, though they cannot prove exactly what the Nazca did.
Some scholars have also noted that the larger figures tend to be built from a limited set of line lengths and repeated units, which fits a system of measurement based on a standard unit. Opinions differ on how far this can be established from the surviving designs, so it is best treated as a suggestion.
One continuous line
Many of the animal outlines are drawn with a single line that does not cross itself and returns to where it began. This feature has been interpreted in several ways. For some researchers it suggests that figures were meant to be walked, with a person following the line from the entrance to the end. For others it is a drawing convention, similar to continuous lines found in other Nazca art. Either explanation is consistent with making the figure by pulling a cord along a planned path.
Dating the designs
The geoglyphs are dated mainly by indirect methods, since the act of clearing stones leaves no organic material behind.
- Pottery. Fragments of Nazca pottery are scattered on and beside many lines and figures. Nazca ceramics change style in a sequence that specialists have divided into phases, so the pieces give a rough period. The same logic of comparing styles underlies pottery seriation in archaeology more widely.
- Wooden stakes. Stakes found at the ends of lines can be dated with radiocarbon dating. Results from the wood place some of the work in the first millennium CE, which fits the pottery. Radiocarbon results come with a range of uncertainty, so they are quoted as approximate spans.
- Other techniques. Researchers have also used methods that estimate when buried material was last exposed to light, applied to sediments at some sites, especially near Palpa.
Together these point to work stretching over many centuries, with the older hillside geoglyphs at Palpa predating the Nazca period and many of the plain’s designs belonging to the Nazca culture.
Surveying today
Modern researchers combine ground survey with photographs from aircraft, balloons, kites and drones, along with satellite images. Older maps were drawn by walking and measuring, work that earned an enduring reputation for the researcher Maria Reiche. Newer imaging has made the process faster and has located additional, fainter designs. These approaches belong to the wider field of archaeological methods, which rely on several kinds of evidence at once because any single technique has limits.
What this means
The practical lessons are simple. The designs could be made by people on the ground, using stones, cord and stakes, and there is physical evidence that they were. There is no need to assume any lost technology or outside help. The harder questions, about meaning and use, lie outside what the construction method can answer, and the next step in understanding is to match the lines with the lives of the people who made them.