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Water in geopark

Jizera - upper flow

Pot-holes are called circular or elliptical depressions plan on width and depth of a few decimetres to meters in rocks rock bottom under the glacier, in the channels of larger rivers and streams, usually in areas with high water flow (rock sills, waterfalls), where the river backward erosion zone outperforms more resistant rocks. In the vertical section are half-cyrcle, conical bowl or depressions in the rock. Arise evorsion (whirlpool) activities of water that carries them sand and boulders, their particle rotational motion polished to bottom and sides hollows. The condition of the relatively fine-grained, compact and very fractured rock. They arise most recently, in the Quaternary, rarely can be up to Pleistocene.

The upstream Jizery, where this river carries great power and enough material for evorzní activities are few places where giant pots arise. The first is Jizerský mine where pots arise rule. Other locations of pots are Burgenland and Ponikla where the basement rock graphitic phyllite and quartzite and metalydity. The last places where the pots are formed flow Jizery Lower Sytová and Háje over Jizerou which occur in melafyrech. But the greatest of these natural creations that can already be described as a giant boilers (up to size 7×5.5 m, depth 3 m), is located in the bed of Mumlava waterfall east of Harrachov. Here, however, incurred in metamorphic rocks as in most of the previously mentioned sites, but in the medium-grained porphyritic granite Krkonoše-Jizera granite massif. Pot-holes can evolve differently perfect find at other places in the region, but these sites are outside the geopark.

GPS position

N 50° 37.467', E 15° 26.460'



Geopark UNESCO Český ráj
Jiří Vlasák