Sailing stones

in #stones6 years ago

Sailing stones

Hi friends, I hope you're fine? Last night, I saw a report on the Sailing stones, it is still challenging as a phenomenon, so I wanted to share it this morning.

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Sailing stones are a geological phenomenon, rocks move leaving long traces along the smooth soil of a valley, without human or animal intervention. They have been observed and studied in California around Racetrack Playa in the Death Valley, where the number and length of furrows due to these movements are particularly notable. The forces at the origin of their movements are perfectly known.

Most of the moving stones form on a hillside of 260 m of dark dolomite at the end of Racetrack Playa, but some are magmatic rocks from the surrounding slopes.

Traces are often a few meters to several tens of meters long, 10 to 30 cm wide and less than 2 cm deep. The stones move only every 2 or 3 years and most traces develop for 3 or 4 years. Stones that have rough contact with the ground leave straight and striated furrows behind them, while smooth stones change direction.

Sometimes a stone spills, resting on another face on the ground and leaving a different trace behind it.

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Traces differ in both directions and lengths. Stones that run close to each other can move parallel for a moment, before one of them suddenly changes direction to the left, to the right, or even back in the direction from where she was coming. Lengths and speeds of movement also vary; 2 stones similar in size and shape can move identically, then one can continue to advance or stop on the way.

It is thought that a set of specific conditions is necessary for stones to move :

• an area saturated with water but not flooded;
• a thin layer of clay;
• very strong bursts that trigger movement;
• strong sustained wind to keep the stones moving.

Study

Geologists made a map of the region's bedrock in 1948 and found traces.

It was at this time that people began to wonder why these stones moved? Various explanations have been proposed during these years ranging from the supernatural to very complicated ideas. Most of the hypotheses favored by geologists say that strong winds, when the mud is wet, are responsible for it. Some stones weigh as much as a man, so some geologists think they are too heavy to be moved by the winds of the region. They say that a layer of ice around the stone helps to catch the wind or slide like an ice floe.

Geologists began a program to monitor the movement of the Racetrack Playa stones in May 1972. Finally 30 stones with recent traces were tagged and pickets were used to locate their position. Each stone received a name and the changes of position of the stones were noted during 7 years.

They tested the hypothesis of the pack ice by creating around some stones an enclosure. It was made of a 1.7 m diameter, around a walking stone 7.6 cm wide and weighing 450 grams with 7 bars of concrete steel placed about 70 cm from it. If a layer of ice around the stones increased the windward grip or helped the rock movements slide over ice floes, then the steel bars should at least slow down and deflect the movement.

We did not see anything like it; the stone just missed a bar when it moved 8.5 meters northwest out of the pen during the first winter. Two heavier stones were placed in the enclosure at the same time; one moved 5 years later in the same direction as the first but her companion did not move during the study period. This proved that if the ice plays a role in the movement of the stones, then the ice caps around the stones must be small.

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Of the 25 stones monitored during the study, 10 moved during the first winter, of which Mary Ann, the A stone, made the most of 65 m. There were several stone movements during 2 of the 6 study winters. No movement of stones was confirmed during the summer, and some winters no stone or stones moved. After 7 years of follow-up, only 2 of the 30 stones studied had never moved.

Nancy, the H stone 6.4 cm in diameter, was the smallest stone of the study. She also traveled the longest cumulative distance, 260m and the longest trip in a single winter, 201m. The largest stone to move was 36 kg.

Karen, stone J, was a dolomite block 74 cm long and about 50 cm wide and tall, weighing an estimated 320 kg. Karen did not move during the follow-up period. This stone was able to trace its old rectilinear furrow of 170 m thanks to the momentum gained during its initial fall on the wet Racetrack Playa. Karen, however, disappeared shortly before May 1994, probably during the winter of 1992-1993, which was unusually wet. It is considered that a displacement of this stone by human means is unlikely due to the absence of traces that a truck would have left.

It is possible that a sighting of Karen was made in 1994 at 800 m from Racetrack Playa. Karen was rediscovered by a geologist from San Jose in 1996.

Professor John Reid led 6 students from Hampshire College and the University of Massachusetts at Amherst for further study in 1995. They found great similarities between the traces of the stones that had moved in the late 1980s and those of the winter 1992-1993.

It was almost completely proved that at least some stones had moved on ice patches that could be up to 800 m wide. Physical evidence was based on striated ground strips that could only be caused by thin layers of moving ice. Thus we think that the wind and the ice blades are the causes of the movements.

The physicists who studied this phenomenon in 1995 found that the winds blowing on the surface of Racetrack Playa could accumulate and thus be intensified. They also found that boundary layers, areas just above the ground where winds are slower due to friction with the ground, on these surfaces can sometimes be only 5 cm.

This means that stones only a few centimeters high receive the full force of ambient winds and gusts, which can reach 140 km / h during winter storms. Such bursts are thought to initiate movement, and momentum with sustained winds allows movement to continue, probably at the speed of a slow-moving man. It can be recalled that approximately half of the force required to trigger the movement of a stone is sufficient to keep it moving.

We therefore favor the hypotheses concerning the wind and ice sheets about these slippery stones.

A study published in 2011 proposed that small patches of ice form around stones and that, when the water level rises locally, the stones are slightly released from the soil layer, which reduces the reaction forces and rubbing with it. Since this effect is dependent on a reduction of friction and not an increase in wind gain, it is not necessary for these slippery ice sheets to be of a large surface, if the ice is in the air ideal thickness since the minimal friction allows stones to be moved by arbitrarily slow winds.

This mode of travel was confirmed in 2014, when a team composed of a biologist, an engineer and a cameraman was able to film in an accelerated manner (time-lapse shooting) the first images of the stones. moving.

https://www.washingtonpost.com/video/national/health-science/timelapse-video-shows-death-valleys-sailing-stones/2014/08/28/f2c2312a-2ec6-11e4-be9e-60cc44c01e7f_video.html?utm_term=.68a003032782

(Video source)

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@lndesta120282 I have not heard about this before. This is an unusual phenomenon. I immediately remembered an excerpt from the movie pirates of the Caribbean :) But if you are serious then where I live I have an ease and floating stones from Kiev. It is believed that the stones sailed on the water. Now these stones grow in the form of a cross directly from the ground. This is an unusual phenomenon and people read that these stones heal.
But the sail stones of the valley of death that you told about are really of great interest. This is not something we can see every day.
Thank you

I heard it for the first time .that's the miracles of nature
Informative article☺

stones....it's the beauty of natute.

love it..
resteem done

nice follow you blog and vote thanks.

Thank you for sharing us about sailing stone knowledge . Before i hadn't knowledge about it.

🎉 Congrats 🍾

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It is a success, you truly deserved. It is an achievement you have truly earned. Well Done.

its really interesting i really enjoyed your post thanks for sharing.

Weathering of rocks is a contributing factor to sailing stones.
This might seem almost theoretical but apparently, is practical in occurrence.
Forceful weathering of rocks such as Mechanical weathering which is caused by agents such as wind and water could hurl rock samples hundreds of miles away irrespective of their sizes.

Amazing nature& photography thanks for sharing....

Great article @indesta120282. Heard about moving stones for the first time. Oh my god! Earth is filled with unique and mysterious details.

You are always making a great article
I hope you will visit my page and support me
Thank you

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