Two "Anomalies" Detected In Egypt's Menkaure Pyramid Using Electrical Resistance Tomography

A team of researchers studying the pyramids of Giza using non-invasive techniques believes they have identified two new "anomalies" in the Menkaure Pyramid.

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The Menkaure Pyramid, built for Pharaoh Menkaure, who ruled between 2490 and 2472 BCE, is the smallest of the pyramids at the Giza site in Egypt. It is also the least-disturbed of the pyramids since the Old Kingdom, the period spanning 2700–2200 BCE.

"From 1906 to 1910, Reisner excavated the pyramid complex and uncovered evidence revealing a more intricate and dynamic history than its architectural design suggests," the team explains in their new study. "This archaeological insight into the life cycle of a pyramid has raised as many questions — if not more — than those associated with the two larger pyramids at Giza."

Despite this, the Menkaure Pyramid remains less studied than the larger Khufu Pyramid, something which the team at ScanPyramids wanted to correct. 

 

One question raised whilst investigating the pyramid is its unfinished granite cladding. While the designers are thought to have originally intended to cover the entire structure, only seven rows of blocks lay preserved at the pyramid's base. The team believes that these could be clues to the existence of a second entranceway into the ancient structure.

"Recently, the potential existence of a second entrance to the pyramid has been proposed based on visual similarities between sections of granite cladding on the Eastern face and those around the main entrance on the Northern face," the team writes. "While most granite blocks have roughly finished surfaces, these two areas stand out with well-polished, accurately fitted blocks."

With ancient pyramids, people get pretty angry when you start smashing down walls. To investigate the hypothesis and potential voids hidden behind the block, the team used a number of non-invasive techniques, including ground-penetrating radar (GPR), ultrasonic testing (UST), and electrical resistivity tomography.

 

While maybe not as cool as muon tomography, using these methods, the team was able to take a look behind these unusually well-polished and smooth stones.

"The images revealed two anomalies directly behind the polished granite blocks, which would indicate the presence of air-filled voids," the authors explain. "This interpretation was supported by a series of numerical simulations that considered various possible scenarios under real-world conditions."

The anomalies, labelled A1 and A2 for ease, are believed to be air-filled cavities. Though these methods of assessing their dimensions are complex and open to interpretation, they appear to be fairly sizeable.

"After processing and applying the joint interpretation to the field data, two main anomalies, A1 and A2, were identified behind the granite blocks of the Eastern face. It was found that anomaly A1 has the approximate dimensions of 1.5 m (4.9 ft) × 1.0 m (3.3 ft) and starts at a depth of 1.35 m (4.4 ft), while the approximate dimensions of anomaly A2 are 0.9 m (3.0 ft) × 0.7 m (2.3 ft) starting at a depth of 1.13 m (3.7 ft)," the team write. 

"Based on extensive 2D ERT, GPR, and UST simulations, as well as IF, it was concluded that both anomalies likely represent air-filled voids within a limestone medium, beginning directly behind the outer granite casing of the Eastern face. Notably, anomaly A1 is located behind a high resistive trapezoid granite block."

Though that is interesting, the team stresses that the results are open to interpretation, and they were limited by the penetration depth of the methods used. Nevertheless, it appears that there may be another entranceway to the overlooked pyramid, which is certainly worthy of further investigation.

"Following the significant validation of a hidden corridor in the Pyramid of Cheops in 2023, ScanPyramids has once again succeeded in making an important finding in Giza," Christian Grosse, professor of non-destructive testing at the Technical University of Munich, added in a statement.

"The testing methodology we developed allows very precise conclusions to be drawn about the nature of the pyramid's interior without damaging the valuable structure. The hypothesis of another entrance is very plausible, and our results take us a big step closer to confirming it."

The study is published in NDT & E International.