The Channel Tunnel
Much more than a tunnel, a journey through time and an exceptional geological history.
Geosite details
Under the English Channel, an ancient link links France and England: a huge layer of chalk formed millions of years ago. It is this rock, shaped by time, that has made it possible to build the longest underwater tunnel in the world.
100 million years ago, a warm sea covered Europe. Billions of tiny algae have left their calcareous skeletons here, which, over the ages, have accumulated and compacted to give rise to chalk. Later, movements of the Earth’s crust lifted these layers, creating the cliffs of Dover and Cap Blanc-Nez.
But 450,000 years ago, a glacial lake broke through this natural barrier, triggering a huge flood that carved out the English Channel and separated Britain from the continent. This ancient connection is still visible through the white chalk cliffs of Dover and Cap Blanc-Nez, which share the same geological origin.
Digging a tunnel under the sea required relying on this geological history. Only an impermeable rock could guarantee the stability of the structure: blue chalk, richer in clay, was chosen to prevent water from seeping in.
The Transmanche Geopark and Eurotunnel have established a partnership to highlight the region’s unique geological heritage, a symbol of the connection between France and England. The Channel Tunnel is not only a technical feat, it is also a testament to the deep connection between man and the Earth, reconnecting two formerly united territories.
Photo credit: Eurotunnel