How is an archaeological excavation done?

1. An archaeological site can be discovered by chance (for example, during public works) or through topographic and cartographic analyses, aerial photographs, electromagnetic detectors or other geoscientific methods. The area is usually explored by teams ranging from three to 80 people, depending on the scope and budget of the project.

two. The work does not usually have a defined duration – to avoid the strong sun and rain, for example, some sites are analyzed only in a few months of the year, over several years. Before starting the excavation itself, the land must be cleared, removing plants and stones, and leveling it. Afterwards, stakes are used to delimit the area, which can vary greatly – in general, between 900 and 1,200 m2

3. Then comes the probing, when archaeologists look for evidence of human occupation on the surface. For example, pottery shards and lithic artifacts (made of stone), such as hatchets, knives and cleavers. At this stage, the excavation does not go beyond 5 cm in depth, and is done with common trowels.

4. Findings determine the “potential” of certain areas. The land is then divided into squares (usually 1 m on a side). Thus, it is easier to catalog where each piece was found. Each quadrant is the responsibility of an archaeologist (student or professor-researcher), who works under the supervision of a coordinator – the most experienced of the team. Some teams have engineers, architects, geologists, bioanthropologists, anthracologists and botanists to contextualize the discoveries

5. In addition to trowels, other lightweight tools such as trowels are used. They also take a shovel, sieve and bucket because all the land removed is sifted and set aside. The soil is cut into very thin layers (10 or 20 cm on average) so that no material is destroyed. Another option is to dig until you notice changes in the type of soil found, respecting the natural layers of the soil. The depth of the site varies a lot – there are places in France where excavations advance only 10 cm per year!

6. All squares are always deepened to the same level. When an archaeological material is finally found, the professionals carry out a meticulous job called pickling. They clean the object gently with brushes, then take pictures at various angles and/or draw it to scale, measuring height, width and depth.

7. Only then is the relic removed from the ground, packed in a plastic bag, labeled, cataloged and sent to a laboratory. There, the dating (definition of “age”) will be carried out, measuring the amount of carbon-14 present: the less the object has, the older it is. On average, one month of fieldwork yields material for one year of laboratory research.

8. Once the excavation is complete, the site is covered with tarpaulin or crushed stone. The removed earth is returned over the excavated site. This is so that, in the future, other scholars can identify whether the area has already been altered by archaeological interventions. All collected material now belongs to the Union, under the curatorship of Iphan (National Historical and Artistic Heritage Institute)

First Brazilians
The most famous archaeological site in the country is in Piauí

Excavated from 1978 to 1988, Toca do Boqueirão da Pedra Furada helped reconstruct the history of man’s presence in the region from around 60,000 to 6,000 years ago. It is the most complete stratigraphy (identification of distinct characteristics of human occupations in the soil) found until today in the Americas. Other important sites in the world are those of Sima de los Huesos (Spain), Monte Verde (Chile), Yucatán (Mexico) and Easter Island

SOURCES Levy Figuti and Paulo DeBlasis, professors at the USP Museum of Archeology and Ethnography, and Antonio Canto, president of the Archaeological and Social Research Sector (Sepas)