The Winged Victory of Samothrace, in Parian marble (c. 200-185 BCE). Louvre Museum
© N. CHARLES
Is the cathedral a geological object?
It would certainly be a little simplistic to think of a cathedral as a natural geological system. But if we confine ourselves to the physical reality of these huge buildings, leaving aside their artistic or spiritual dimension, we see a heterogeneous geological environment, a motley collection of elements where the most diverse and often the most incompatible materials lay side by side: stones of many origins, ages and textures, an infinite variety of mortars, plasters, limes, cements, paints, wood, metals or glass, and so on.
A cathedral is also a constrained environment, exposed to strong temperature contrasts, rain, frost and wind, and subject to a wide range of anthropogenic pressures: air and rain pollution, plus contamination from the ground water in contact with the foundations.
The example of the cathedral illustrates two main ways in which the Earth sciences can help us understand and preserve our cultural heritage: the origin of materials and the evolution over the centuries of objects shaped by humans.
Tracing materials back to their source
The materials used in the sculptures and monuments retain a genuine geological signature. Petrographic and geochemical analyses help to identify the origin of the stones. In particular, these methods have determined that the marble in different parts of the Winged Victory of Samothrace in the Louvre come from different Greek quarries. There are few, if any, reliable written documents linking a work of art to its place of creation and the source of its materials. Historically, this lack of sources was common before the 16th century. This is where geoscientific methods make a significant contribution.
Standing the test of time
From the moment they are built, stone monuments are subject to the same stresses as any other geological object: physical, chemical and biological weathering and erosion. The geologist's expertise complements that of the restorer, and there are many examples of fruitful collaboration.
Understanding and conserving cultural heritage, particularly buildings, requires a wide range of disciplines. Here, it is often the humanities that ask the questions and the geosciences that try to answer them.
Cover of Issue 29 of the Géosciences journal
© BRGM
Géosciences No. 29: Talking about Earth
“Talking about Earth” may seem to be a surprising expression for a scientific journal. However, it is by telling this story that the geological history of our planet is most clearly understood. And when faced with the amazing phenomena that led to the formation of the rocks beneath our feet, it is often wonder that dominates.
This 29th issue of BRGM's Géosciences journal takes a slightly different angle from its predecessors, exploring the beauty of the landscapes that surround us, inspiring the arts through science, passing on the Earth sciences to young people and the general public, and protecting our geological heritage.
