Looking into the Earth An Introduction to Geological Geophysics

Archaeology is the study of how humans lived in the past, so no direct observation is possible. For this reason, information about how – and when – people lived has to be deduced from what they have left, both intentionally – such as monuments and written records – and, just as important, incidentally, in traces of buildings, fortifications, field systems, and so on, now often buried. Unravelling the sometimes long and complicated history of an archaeological site often requires the skills of a detective applied to meticulous and painstaking excavations. To aid the investigation, the archaeologist can call upon various techniques (i) to help find or map a site, (ii) to help date the site and its artefacts, and (iii) to help characterise artefacts, such as analysis of their materials to help find their source. Geophysics has a large contribution to make to the first two of these, and a lesser one to the third.

Dating is obviously important to understanding how cultures develop or relate to one another. For example, it was once thought that the builders of Stonehenge derived their culture from the ancient cultures of the eastern Mediterranean, such as ancient Greece, until carbon dating showed Stonehenge to pre-date them. The dating methods most used in archaeology are those suitable for younger materials (described in Section 15.12), but the potassium–argon method is the main method for dating early hominids, mainly in Africa where they extend back over 4 Ma.