Preserving Holocaust history: Geophysical investigations at the Ponary (Paneriai) extermination site

Abstract

Holocaust mass grave sites in eastern Europe can be difficult to investigate due to a paucity of historical documentation relating to the events and because the use of traditional invasive archaeology methods raises concerns around the disturbance of the remains of Jewish people. When combined with other lines of evidence, including historic photos and eyewitness testimony, noninvasive geophysical methods help to effectively identify and demarcate buried features at Holocaust sites, limiting unnecessary excavations. Between 1941 and 1944, as many as 100,000 people were murdered at the Ponary (Paneriai) extermination site in Lithuania, but many critical details of the site layout during this period are still to be resolved, including the location of some of the mass graves and confirmation of an escape tunnel that was used by slave laborers to escape captivity and certain death at the site. At Ponary, a combination of electrical resistivity tomography (ERT) profiling, limited ground-penetrating radar data, and bare-earth elevation data (from a light and distance ranging data set) was used to confirm the location of a large unmarked mass grave with a diameter of approximately 25 m and depth of approximately 4 m. Additional ERT profiling at a second location imaged the entrance to an escape tunnel previously uncovered by an archaeological excavation in 2004, and it detected an approximately 5 m section of the continuation of the tunnel, approximately 33 m away from the tunnel entrance. The geophysical results are supported by evidence from limited archaeological excavations, historical photographs, eyewitness descriptions of the site layout, and testimonies from the few survivors who managed to escape Ponary.