During the Paleozoic Era there was another mountain range in the place of the current Mount Blanc. Over the years it was eroded and filled in with several seas. Marine sediments have been uncovered by present day geologists. Then 40 million years ago a new mountain range formed due to a folding in the earth’s crust in this part of France.
Mount Blanc took its present general shape about 15 million years ago as this fold in the earth’s crust reached its climax. More recently during the Quaternary Era, many many glaciers reshaped the topography of the land. Much more recently (between the years of 1590 and 1645) Chamonix experiences some very severe winters. The glaciers advanced to their furthest points. The Mer de Glace (talked about later in more detail) almost blocked off the main valley.
The last recent advance of the glaciers took place in 1825 and 1826. Since then the glaciers have been receding every year. One
interesting note is the natural phenomenon that took place at the old village of Les Bois. This village was evacuated in 1825 because of the close proximity of the moving ice fields. One glacier that was near this town ended in a 120 feet wall of ice. This was a tourist attraction for many years, until the glacier completely retreated back up into the mountains.
An event that happened in 1820 was the death of 3 guides. Initially five guides plunged into a deep crevasse and three of them were never seen again. A geologist predicted that if the glacier kept advancing at a particular rate of speed the bodies would be found in about 35 to 40 years. Amazingly his calculations proved true as 41 years later the bodies were found at the edge of the glacier.