Creeping stones, also called sliding or moving rocks, a unique geological phenomenon, discovered on the dry lakebed of Racetrack Playa in Death Valley (California, USA). Stones move slowly on the clay bottom of the lake, as evidenced by long traces that remain after them.
They move on their own without the assistance of living beings, but no one has ever seen or recorded the movement of the camera.
Most of the sliding stones fall to the bottom of the dry lake with the dolomite hill with a height of 260 meters, located on the southern limb of the dry lake Racetrack Playa. The weight of stones up to several hundred kilograms. Traces trailing behind them, have a length of several tens of meters, width from 8 to 30 cm and a depth of only 2.5 centimeters.
The stones are set into motion only once in two or three years, and most of the traces is stored for 3-4 years. Stones with a ribbed bottom surface to leave more straight tracks, but the stones lying on the flat side, wander from side to side.
Stones sometimes turn over, which is reflected in the size of their footprint. It is assumed that the spontaneous movement of the stones, you need to meet several conditions: moist, but not flooded surface, a thin layer of clay, strong gusts as initiating force strong constant wind to continue moving.
Prior to the beginning of the XX century the phenomenon was explained by the supernatural, then in the formative period of electromagnetism has been suggested on the effects of magnetic fields, which, in General, did not explain anything.
Most of the hypotheses agreed on the fact that the wind at the wet surface of the bottom of the lake partly explains the phenomenon. In 1955, geologist George Stanley of the University of Michigan published an article in which he claimed that the stones are too heavy, and the wind is unable to move them. He and his colleague proposed the theory that during the seasonal flooding of the dry lake on the water forms an ice crust, contributing to the movement of the stones.
For 7 years, during which recorded the position of the stones, scientists have created a model in which in the rainy season in the southern part of the lake accumulates water, which is distributed by the wind on the dry lake bed, wetting its surface. The result is a solid clay soil much liked the friction coefficient is sharply reduced, which allows the wind to budge even one of the large stones (Karen), who weighed about 350 pounds.
We also tested the hypothesis of transport by ice. Water spreading by the wind at night can be covered by a layer of ice located on a water way the stones are frozen into the ice layer. The ice around the stone could increase the interaction cross section with the wind and help move the stones along the water streams.
In 1993, Paul Messina of the California state University defended a thesis on the subject of moving rocks in which it was shown that in General, the stones did not move in parallel. According to the researcher, this confirms that ice does not contribute to the movement.
After studying the changes of coordinates 162 of the stones (held by GPS), it was determined that to move the boulders do not affect neither their size nor their form. It turned out that the character of the movement to a large extent determined by the position of the boulder lake Racetrack Playa. According to the model the wind over the lake behaves in a very complex manner, in the center of the lake even forming a vortex.
In 1995, the group led by Professor John Reid noted the high similarity of the traces of the winter of 1992-93 with traces of the late 1980s. it has Been shown that at least some of the stones were moving with the flow of the ice-covered water, and the width of the ice crust was about 800 m, as evidenced by the characteristic signs, scratched in a thin layer of ice. It is also shown that the boundary layer where the wind slows down due to contact with the ground, such surfaces may be 5 cm, which means that the winds (which in winter reaches 145 km/h) even at very low stones.
The theory, which would explain why standing stones can move in different directions when others stand still, yet. It is also unclear why the stones "scattered" around the bottom of the lake, whereas regular wind would move them to one of the edges of the lake.
In 2010, a group of students and postgraduates of different educational institutions of the USA took part in the expedition called LPSA Death Valley Excursion. Before the expedition's task was to develop new hypotheses and test existing ones. Participants suggested that around every boulder locally growing sort of collar made of ice, causing the stone is at least partially lifted, and reducing its friction on the ground. The streams of water that strikes the icy crust, can also be turning over rocks from side to side.
However all points over "and" explanation of the mysteries creeping of stones still not placed...