A new method for seeing buried buildings
Modern archaeology increasingly makes use of scientific methods and tools. Magnetometry, which studies variations in the earth’s geomagnetic field, can reveal ancient structures and objects hiding beneath the surface. As a nondestructive method, magnetometry in archaeology measures the magnetic fields of different materials buried underground, without even having to scrape the surface.
In the Summer 2023 issue of Biblical Archaeology Review, Andrew Creekmore introduces the use of magnetometry in archaeology. His article, “Seeing into the Ground,” explains how magnetometry works and demonstrates what results this novel method has brought so far at Tell es-Safi, the site of the biblical Gath in southern Israel. Creekmore, who is Professor and Chair of the Department of Anthropology at the University of Northern Colorado, focuses on the application of geophysical methods in archaeology. He joined the Tell es-Safi team—led by Aren Maeir of Bar-Ilan University—in 2017.
Creekmore reminds readers that the modern, careful approach to excavating ancient sites means that even a decade of digging may not expose more than just a few buildings. Although this may bring forth an immense volume of archaeological data, it usually fails to provide a good understanding of the organization of ancient cities. As a nondestructive method that can survey large areas of any given site, magnetometry in archaeology serves to reveal buried architecture and archaeological features without having to fully excavate them.
So how does magnetometry work in archaeology? “Magnetometers measure the magnetism of soil, stone, and buried features located up to 6 feet below the surface. … Soils, stones, and other materials are naturally subject to magnetization in which they develop a magnetic field induced by the earth’s magnetic field. Archaeological features such as foundation trenches, storage pits, and mud walls have differing levels of magnetization. This creates contrasts that we can sense and map with magnetometers,” explains Creekmore. “If soils, stones, or other materials are heated to a high temperature, they develop a higher magnetization. Thus, hearths, kilns, fired bricks, volcanic rocks (e.g., basalt), and burned structures represent highly magnetized features that can be sensed by magnetometers.”
This is how a light and portable instrument like a magnetometer can reveal entire cities, without the need to disturb the site through excavation, which is by definition destructive. One of the few limitations of magnetometer survey, on the other hand, is that subtle features may be obscured by highly magnetic geologic or modern materials. As Creekmore notes, “Excavation and surface collections are still necessary to date buried features and confirm interpretations derived from magnetic data.”
To explore the use of magnetometry in archaeology and to observe its use at the site of biblical Gath, read Andrew Creekmore’s article “Seeing into the Ground,” published in the Summer 2023 issue of Biblical Archaeology Review.
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