Pisecny presyp Pisty / Pisty Sand Dune EarthCache

Hned za vesnici Pisty muzeme najit krasny pozustatek polabske duny. Nachazi se na rozloze cca 3.7 ha a byla jako Pisecny presyp u Pist vyhlasena v roce 1951 narodni pamatkou.

Duna byla zformovana behem Pleistocenu (starsi oddeleni ctvrtohor cca 1.8 milionu let az 10 000 let pr.n.l.) jemnym navatym piskem. Klima v plestocenu bylo poznamenano obakujicimi se doby ledovymi, behem kterych v nezamrzlych castech sveta doslo k logickemu ubytku vody v rekach, kdyz voda byla zamrzla v ledovcich. Snizeni hladiny rek samozrejme prispivalo k erozim, stejne jako opetovne vzedmuti hladiny pri teplejsim obdobi. Material reky odnasely a na klidnejsich mistech vyplavovaly a tak vznikaly terasy. Na nich eroze na drobnejsi castecky nadale pokracovala a ty nejjemnesi byly odnaseny vetrem, diky kteremu byla vytvorena velka duna.

Do dnesni doby samozrejme vetsina duny zarostla vegetaci, ale porad velika cast (na rozdil napriklad od dun u Svaravy - Tynec nad Labem, ktere jsou zarostle cele) zustala odkryta.

V pisecne "pousti" se samozrejme libi piskomilnym spolecenstvim rostlin a hmyzu. Jake to jsou muzete nastudovat na nedaleke informacni tabuli.

Next to a village Pisty is located one of the last sand dunes around river Labe.

Dune occupies area of 3.7 ha and as Natural monument was publicated in 1951.

The dune was formed in Pleistocene by blowing sand. The material like stones and gravel sand was carried here during the centuries by river Labe made the terrace. Then material eroded and finally winds done their work - ultra-fine grained sand was blowed away and formed the dune.

The Pleistocene is the epoch from 1.8 million to 10 000 years BP. The name pleistocene is derived from the Greek pleistos = "most" and kainos = "new".

Pleistocene climate was marked by repeated glacial cycles where continental glaciers pushed to the 40th parallel in some places. It is estimated that, at maximum glacial extent, 30% of the Earth's surface was covered by ice.

The effects of glaciation were global. Antarctica was ice-bound throughout the Pleistocene as well as the preceding Pliocene. The Andes were covered in the south by the Patagonian ice cap. There were glaciers in New Zealand and Tasmania. The current decaying glaciers of Mount Kenya, Mount Kilimanjaro, and the Ruwenzori Range in east and central Africa were larger. Glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains. (wiki)

The warner and colder times had ged. In the colder times there were less water in the rivers, because water was frozen in the glaciers. Repetitious decreasing (in cold times) and raising (in warmer time) of the river level caused erosions. Material was carried by rivers and formed terraces. Progressive erosions caused, that small seeding could be blowed away and formed the dunes.

In our times Pisty dune is only remaining of the great dunes around river Labe. In last 10 000 years most of the dunes were grown by vegetation.

thx Milancer for photo