Sailing Stones – Still a mystery !
Racetrack Playa is a seasonally dry lake (a playa) located in the northern part of the Panamint Mountains in Death Valley National Park, California, U.S.A.. It is famous for ‘sailing stones’, rocks that mysteriously move across its surface.
The area receives about two inches of rain in a normal year and is surrounded by mountains that funnel water down into the playa. The soil forms a slick mud when wet and the wind may then be able to push small stones across the playa, but what about the larger rocks? Some of these rocks weigh several hundred pounds.
The mysterious moving stones of the packed-mud desert of Death Valley have been a center of scientific controversy for decades. Rocks weighing up to hundreds of pounds have been known to move up to hundreds of yards at a time. Some scientists have proposed that a combination of strong winds and surface ice account for these movements. However, this theory does not explain evidence of different rocks starting side by side and moving at different rates and in disparate directions. Moreover, the physics calculations do not fully support this theory as wind speeds of hundreds of miles per hour would be needed to move some of the stones.
The truth: No one knows for sure exactly how these rocks move – although a few people have come up with some pretty good explanations. The reason why their movement remains a mystery: No one has ever seen them in motion!
About Racetrack Playa
Racetrack playa is lake bed that is almost perfectly flat and almost always dry. It is about 4 kilometers long (2.5 miles – north to south) and about 2 kilometers wide (1.25 miles – east to west). The surface is covered with mudcracks and the sediment is made up mainly of silt and clay.
The climate in this area is arid. It rains just a couple of inches per year. However, when it rains, the steep mountains which surround Racetrack Playa produce a large amount of runoff that converts the playa floor into a broad shallow lake. When wet, the surface of the playa is transformed into a very soft and very slippery mud.
Are They Moved by People or Animals?
The shape of trails behind the rocks suggest that they move during times when the floor of Racetrack Playa is covered with a very soft mud. A lack of disturbed mud around the rock trails eliminates the possibility of a human or animal pushing or assisting the motion of the rocks.
Are They Moved by Wind?
This is the favorite explanation. The prevailing winds that blow across Racetrack Playa travel from southwest to northeast. Most of the rock trails are parallel to this direction. This is strong evidence that wind is the prime mover or at least involved with the motion of the rocks.
Strong wind gusts are thought to nudge the rocks into motion. Once the rock begins to move a wind of much lower velocity can keep the rock in motion as it slides across the soft and very slippery mud. Curves in the rock trails are explained by shifts in wind direction or in how the wind interacts with an irregularly shaped rock.
Are They Moved by Ice?
A few people have reported seeing Racetrack Playa covered by a thin layer of ice. One idea is that water freezes around the rocks and then wind, blowing across the top of the ice, drags the ice sheet with its embedded rocks across the surface of the playa.
Some researchers have found highly congruent trails on multiple rocks that strongly support this movement theory. However, the transport of a large ice sheet might be expected to mark the playa surface in other ways – these marks have not been found.
Other researchers experimented with stakes that would be disturbed by ice sheets. The rocks moved without disturbing the stakes. The evidence for ice-sheet transport is not consistent.
These are some amazing visuals of Sailing Stones
Source : wikipedia