Sailing Stones?!!

Sailing Stones

Sailing stones, also known as moving rocks  are a geological phenomenon where rocks move and inscribe long tracks along a smooth valley floor without human or animal invention. This moving rocks have been observed and studied in various locations, including Little Bonnie Claire Playa in Nevada and most famously at racetrack Playa, Death Valley National Park, California. Where the number and length of tracks are notable

Stones with rough bottoms leave straight striated tracks, while those with smooth bottoms tend to wander. Stones sometimes turn over, exposing another edge to the ground and leaving a different track in the stone’s wake.

Trails differ in both direction and length. Rocks that start next to each other may travel parallel for a time, before one abruptly changes direction to the left, right, or even back to the direction from which it came. Trail length also varies two similarly sized and shaped rocks may trafel uniformly, then one could move ahead or stop in its track.

At racetrack playa, these tracks have been studied since the early 1900s, yet the origins of stone movement were non confirmed and remainded the subject of research fpr which several hypotheses existed. However, as of august 2014, timelapse video footage of rocks moving has been published, showing the rocks moving at hight wind within the flow of thin melting sheets of ice. The scientists have thus identified the cause of the moving stones to be ice chove.

News articles reported the mystery solved when researchers observed rock movements using GPS and time-lapse photography. The research team witnessed and documented rock movement on December 20, 2013, that involved more than 60 rocks, with some rocks moving up to 224 m between December 2013 and january 2014 in multiple movements events. These observations contradicted earlier hypotheses of winds of thick ice floating rocks off the surface. Instead, rocks move when large ice sheets a few millimeters thick floating in a ephemeral winter ponf start to break up during sunny days. These thin floating ice panels, frozen during cold winter nights, are driven by light winds and shove rocks at up to 0,3 km/ h. Some gps measured moves lasted up to 16 minutes, and a number of stones moved more than five times during the existence of the playa pond in the winter.

The movement of the rocks results when large ice sheets a few millimeters thick floating in a ephemeral winter pond start to break up during sunny days. Frozen during cold winter nights, these thin floating ice panels are driven by wind and shove rocks at speeds up to 5 meters per minute.

A balance of very specific conditions is throught to be needed for stones to move :

-a flooded surface

-a thin layer of clay

-ice floes

-warming temperatures causing ice breakup

Sumber: 

https://en.wikipedia.org/wiki/Sailing_stones-wind