SOSNOWIEC, POLAND — Today my colleague Michał Zatoń took me and his family (wife Aneta and son Tomasz) on a tour of the Polish Jura, an upland with spectacular exposures of Jurassic rocks and the castles who love them. Above is the castle I consider most dramatic: Zamek Mirów from the 14th Century. Note the large mass of white bedrock at its base. This is a natural outcrop on which the castle was built. This will be a theme.
Here we see a series of these white rocks jutting dramatically across the landscape. They are Upper Jurassic (Oxfordian) sponge-rich silicified limestones that grew as bioherms (organic mounds) on portions of seafloor elevated because of igneous intrusions below. The sponges loved being raised off the deep seabed and continued to grow upwards. Since many of them were siliceous sponges, after death their silica was mobilized into the surrounding sediment as a cement. This process produced these outcrops of very hard silicified limestones just waiting to host a castle or two.
Conveniently, the rocks can be quarried to produce the stones used in castle construction. Fossils are quite common in the building stones, like this ammonite external mold.
This is a reconstructed castle built on the outcrops. (Zamek Bobolice; also 14th Century in origin.)
Zamek Smoleniu was the smallest castle we visited, but somehow the scariest to climb. Getting to the top of that tower was a challenge.
Zamek Ogrodzieniec was the largest and best known castle we visited today. It is haunted, but I ain’t scared.
The outer fortifications of Zamek Ogrodzieniec have very impressive outcrops of the Oxfordian silicified limestones.
Now what about that mysterious Polish desert? Well, turns out it isn’t a desert in the official sense (it receives a lot of rain), but it sure looks like a desert. Pustynia Błędowska is its name in Polish. It is definitely an odd patch: 32 square kilometers in the midst of rich Polish pine forests. This place is so deserty that the German Afrika Korps trained here before going to northern Africa, and the Polish military uses it as a proxy for Middle Eastern situations. There is a lesson for humanity here as well: In the 13th and 14th Centuries the forest in this area was completely logged to provide charcoal for smelters producing silver and lead ingots. The removal of the trees exposed highly mobile glacial sands, which blew around enough to create dunes and soil too unstable for the trees to recolonize. This is a medieval ecological catastrophe. The Błędów Desert is now protected from human traffic so it has a chance to be absorbed back into the surrounding forests.
