A Resonant Giant
The field of archaeoacoustics examines the role of sound in ancient human societies. At Locmariaquer, this discipline suggests a possibility for the Grand Menhir Brisé, the largest single stone ever erected by Neolithic people. Quarried and transported around 4700 BCE, this monolith of orthogneiss, a type of metamorphic rock, weighed an estimated 280 to 330 tons and measured over 20 meters in length. Geologists have traced the stone's origin to a quarry at least 10 kilometers away, meaning it was moved a significant distance before being raised.
The physical properties of dense, crystalline rock like orthogneiss allow it to resonate when struck. This has led to the hypothesis that the Grand Menhir was a massive lithophone, or "ringing stone." When struck with force, it would have produced a low-frequency sound that could travel for many kilometers, particularly over water. This sound could have been a territorial marker or a navigational beacon for sailors navigating the complex coastline of the Gulf of Morbihan. The entire surface of the stone was worked, or shaped, which may have been done to "tune" its acoustic properties. The menhir stood for several centuries before toppling and breaking around 4000 BCE. While the cause is debated—theories include deliberate destruction or an earthquake—the result was a silent giant.