It was during the first World War that the impact of human warfare on the landscape exponentially increased. Large armies equipped with the most advanced military technology- especially the high energy explosives evolved rapidly - devastated entire landscapes along the Western Front, stretching from the English Channel to the Swiss mountains. One of the most iconic sites of this attrition warfare was the area surrounding the French town of Verdun.

February 21, 1916 the first shell - with a caliber of 38 centimeters and weight of 750 kilograms - was fired by a modified long-range naval gun nicknamed "Long Max". After the German attack, soon French counterattacked. From February to August 1916 in an area of 200 km2 estimated 60 million rounds were fired.

All those explosions destroyed the local vegetation, reshaped and lowered the landscape, but also remixed the natural formed soil-layers and fractured the underlying bedrock - the effects of those few months are still visible today, almost 100 years after the war ended.

The geographers Joseph P. Hupy and Randall J. Schaetzl visited the battlefield of Verdun to investigate how the great war modified the landscape and influenced its further development. The artillery fire changed how and which type of soil can form - so much that the authors suggest that the modern use of bombs and explosives is such a significant erosion factor that it deserves a own term: Bombturbation.

Fig.1. Fort Doaumont, part of the fortifications of Verdun, before 1916 and at the end of April/May 1916 (image in public domain), dotted with explosion craters.

When an average WWI grenade exploded, it excavated a crater with a diameter several meters across and 1-2 meters deep, however large mines excavated also craters 15 m in diameter with depths exceeding 10m.

The explosion fractures the shallow bedrock and redeposit material (soil and rock fragments) on the outer rim of the crater, forming also lenses of gravel-ejecta. With time the barren crater will fill with new sediments, especially litter, from the slowly returning vegetation. As the area of Verdun is characterized also by a shallow water table, many bomb craters filled with water, forming shallow ponds where fine-grained clay and peat accumulates, resulting in water logged soils.

Fig.2. Postbombturbative battlefield of Verdun in 2005, uploaded by user 01.camille on Wikimedia Commons (2005), image in public domain.

In dry craters the fractured bedrock increases the infiltration of water and accelerates the chemical weathering of the limestone. The fissures in the rocks are also a good habitat for earthworms, as the two researchers observed an increased worm activity inside the craters. The earthworms transport incessantly litter and plant debris from the surface to the crater bottoms, where the leaching organic acids will attack the undisturbed rock. In explosion craters the now occurring soils are therefore thicker than in the undisturbed landscape, where thinner "natural" soils occur.

After WWI, the "The War to end all Wars", unfortunately many other - even greater and with more bombturbative power - wars followed. During WWII estimated 1,3 billion kilograms of bombs were dropped on Europe, a number paled by the 1,27 trillion kilograms of bombs and explosives deployed in the Vietnam War. All the conflicts of the 20th century are estimated to have moved billions of cubic meters of earth materials, another erosive legacy of the Anthropocene.

Bibliography:

HUPY, J.P. & SCHAETZL, R.J. (2006): Introducing "Bombturbation," a singular type of soil disturbance and mixing. Soil Science, Vol.171(11): 823-836

HUPY, J.P. & SCHAETZL, R.J. (2008): Soil development on the WWI battlefield of Verdun, France. Geoderma Vol.145: 37-49

HUPY, J.P. & KOEHLER, T. (2012): Modern warfare as a significant form of zoogeomorphic disturbance upon the landscape. Geomorphology, Vol. 157-158: 169-182