Greetings Steemians!
In today’s stage of my tour along the Swabian Jura, I invite you on a little excursion to a natural spectacle that has fascinated since it was discovered. Welcome to the Blautopf.
The Blautopf (german for blue pot) is located at the outskirt of the city of Blaubeuren and forms the exit of the largest cave system in germany's federal state Baden-Württemberg. An underground network more than 12 km long with countless branches, cavities, large halls and narrow channels, below and above the water line. The rainfall of the region trickles into this cave system and exits at the Blautopf with an average outflow of 2'000 liter per second. After prolonged rain the outflow can increase up to 32'000 liter per second, a volume equalling the filling of a standard road tanker! I once had the chance to witness such a peak outflow and I can tell you that the entire Blautopf appeared as if it was boiling. Unfortunately, I had no camera with me back then.
In fact, the Blautopf was once a water fall. But around 150'000 years ago it got buried by a rockfall and became today's underground spring.
The power of the outflow is also a constant source of energy and is used to drive a hammer mill since 1804.
Most of what is known about the cave system behind the Blautopf was revealed by pioneering work of fearless cave divers, such as Jochen Hasenmayer. Hasenmayer found the first air-filled cave after a 1250m long dive behind the Blautopf, named the Mörikedom (Mörike cathedral). Later, Hasenmayer came up with a controversial theory. Hasenmayer proposed that the Blautopf’s cave system connects to another, even larger water network further in the south towards the Alps, one that has persisted since the Cretaceous period and that has never drained. He claims that this other cave system leads to even greater depths so that it may contain vast amounts thermal water. Potentially, a source of huge dimensions for geothermal energy. Experts have largely rejected his claim and yet, his exceptional contributions in the exploration of the Blautopf remain admired without restrictions.
The Blautopf always provided precious drinking water in an otherwise dry region. Remember that the Jura's limestone drains rain water quickly and leaves little on the surface. Thus, humans settled in proximity already since paleolithic times. Ever since the mysterious depth of the Blautopf has quickened the imagination of it’s visitors and it became a place of myths and legends.
Before I close I have once again a little quiz for you. On my photos you can convince yourself of the Blautopf’s eponymous blue color. But what exactly is it that makes the water appear blue? Both, the scientifically most thorough and the most creative explanation will be added to this post and rewarded with 1 SBD each.
EDIT: And here the answer to the Quiz:
- According to Wikipedia:
The water's peculiarly blue color, varying in intensity due to weather and flow, is the result of physical properties of the nanoscale limestone densely distributed in the water. The particles are so small that the so-called Rayleigh scattering of light takes place, preferentially scattering the blue color in the visible light.
- According to @xers (loosely translated into english by me):
The Blautopf's blue results from kyanite, which emerges from the friction of the crystal clear water with fairy dust and subsequently settles at the bottom. The Swabian Jura is well known for the high concentration of fairy dust, which produces an aurora appearance once every year, on June 4th, The aurora attracts the bear population from the surrounding hills and makes them dancing in circles.
Congratulations to 
Thanks for watching and enjoy your day on Steemit!
Shaka
All photos were recorded by myself with an iPhone 6S in April, 2018