The Channel Tunnel
One of the modern engineering wonders of the world, the Channel Tunnel is the longest underwater tunnel in the world and the third-longest train tunnel in the world.
Folkestone
Open all year round
Accessible by public transport
Café
Facilities
- Car parking
- Disabled parking
Geosite details
One of the modern engineering wonders of the world, the Channel Tunnel is the longest underwater tunnel in the world and the third-longest train tunnel in the world.
Tunnelled straight through the geology of the Cross-Channel Geopark, this extraordinary feat has also permanently reconnected France and Britain after over 450,000 years of separation since the Megaflood.
Not content with being an international engineering marvel, the chalk marl that was dug out to form the tunnel was repurposed to create a new piece of land at the foot of the White Cliffs of Dover which has since flourished into a thriving nature reserve, another of our Geosites – Samphire Hoe.
The unique geodiversity of the Cross-Channel Geopark was vital to the success of the Channel Tunnel project, as the layer of ‘chalk marl’ which sits at the bottom of the chalk, just above the older clay, forms an ideal layer for tunnelling through. Whilst chalk has tiny cracks running through it which allow water to flow through, making it permeable, the Marl layer is impermeable due to it being a mixture of clay, chalk and other materials, perfect for keeping the tunnel from filling with water!
