Jubilee, with stalactites: Picture of the Week 5 June 2012

In limestone caves stalactites can take hundreds of years to grow to the size of these hanging above the platform at Sowerby Bridge station in Calderdale.  On concrete they can grow hundreds of times faster. Rainwater mixes with calcium compounds in the concrete mix to form a calcium hydroxide solution. This runs over and through the concrete to form calcium carbonate where it comes into contact with the air. This solidifies into white staining and, where the solution drips, stalactites.

The stalactites in this picture are not actually as old as the sixty year reign of Queen Elizabeth, they could have formed in only four years. However they could be a sign that there is something wrong with the station roof. It needs investigating.

How can you tell a stalactite from a stalagmite? It's in the name, a stalactite hangs downwards, so it has to hang on tight! Meanwhile a stalagmite has to grow upwards all its might, because gravity is against it.