On the 1st picture, a layer of limestone in Els Tres Salts, in the river Llobregat (Sant Fruitós de Bages), in a high water day. The water erodes the limestone and slowly pushes it back. The layer on top is a massive, fine limestone whilst the layer below is a reef limestone.
On the 2nd picture, the usual shell like fracture of the massive limestone. This pattern is repeated in most of fine grain, homogeneous rocks as chert and obsidian -a natural glass. Artificial glasses break in shell shape as well; it is obvious at the bottoms of champagne bottles.
Limestone is a calcareous rock made of mainly calcium carbonate. The most frequent limestones in Bages are arranged in really resistant to the erosion layers. They come from either marine -as the one in Els Tres Salts– or lake origin. Nowadays limestones are mined in quarries as a material for building while, in the past they were used to obtain lime. Marine limestones of Bages contain a lot of macrofossils because they were sourced in reefs.
[photos Florenci Vallès]
- See the potholes in the river shores.