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How WWI Bombs Shattered Bedrock And Changed Geological History

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On the 11th hour, of the 11th day, of the 11th month of 1918, the guns that had thundered for four years fell silent. One hundred years after the end of World War I traces can be still found in the landscape.
«Humanity is mad. It must be mad to do what it is doing. What a massacre! What scenes of horror and carnage! I cannot find words to translate my impressions. Hell cannot be so terrible. Men are mad!» — A French lieutenant at Verdun, who would be killed by a shell.
The war in Europe began as a battle between infantry and cavalry, like in old times, and was believed to be quickly over. However, new weapons, like the machine-gun or heavy artillery, made direct attacks almost impossible as soldiers were killed in their thousands. The war quickly became a war of attrition as both sides dug in a network of trenches and tunnels separated by the “No Man’s Land.”
The «No Man’s Land» of Verdun. More than 60 million rounds were fired on the battlefield and 600,000 soldiers killed here in the summer of 1916. Public domain image. Anonymous
Front-line trenches, built in a zig-zag to minimize the effect of an explosion in the trench, provided protection against gunfire, but not a direct hit from an artillery shell. Behind the front-line, trenches allowed movements of troops and transport of supplies, with bunkers located in deep dug-outs, 50 feet below ground. Digging trenches and tunnels posed also a problem to the soldiers depending on the encountered rock types.
German field guide on how to constructs trenches and tunnels according to encountered bedrock geology published in 1920. J. L. Wilser 1920
Along the Western Front in France and Belgium the underground consists of a succession of limestone, mudrock and marlstone. In Ypres and along the River Somme, the ground consists of fine-grained sediments deposited in the sea some 23 million years ago. A short shower of rain and the trenches were full of water, the sides of the trenches were falling in because they were made of little more than clay. During the great battle of Verdun, the troops were ordered to intrench itself on the high plateau of the Còtes de Meuse. Unfortunately, the plateau was underlain by hard limestone and the soldiers were unable to dig trenches there and many lives were lost.
In Verdun alone, more than 600,000 soldiers were killed in the summer of 1916. Estimated 60 million rounds were fired on the battlefield, as the Austria-Hungarian troops tried to overrun the French defense positions. The explosions destroyed the local vegetation, reshaped and lowered the landscape, remixed the soil-layers and fractured the underlying bedrock. The effects are still visible today, almost 100 years after the war ended.
Geographers Joseph P. Hupy and Randall J. Schaetzl visited the former battlefields in France to investigate how the great war modified the landscape. When an average WWI grenade exploded, it excavated a crater 40-80 inches deep. However, large mines excavated craters 600 inches in diameter with a depth exceeding 400 inches. The explosion fractured the shallow bedrock and redeposited soil and rock fragments on the outer rim of the crater, forming lenses of gravel-ejecta. With time, the craters filled with new fine-grained clay and litter from the slowly returning vegetation. The two researchers observed also an increased earthworm activity inside the craters. The earthworms and the decaying plants release organic acids, accelerating the chemical weathering of the limestone. Many bomb craters filled also with water, forming shallow ponds. The two researchers, noting that since WWI the use of bombs and explosives by humans is a significant factor in shaping Earth’s surface, named the erosion effect by human warfare » Bombturbation. «
The battlefield of Verdun 100 years later. Public domain image. Anonymous
I’m a freelance geologist working mostly in the Eastern Alps. I graduated in 2007 with a project studying how permafrost, that´s frozen soil, is reacting to the more visible recent changes of the alpine environment. Studying therefore old maps, photographs and reports, I bec…

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