The Mysterious Moving Rocks Of Racetrack Playa

Moving-rocks-baffle-scientists-11The mysterious moving rocks of Racetrack Playa have puzzled (been impossible to understand or explain) scientists for nearly 100 years.

A playa is a dry lake. The water that used to fill Racetrack Playa evaporated (disappeared into the air) many years ago and left a three-mile-long (4.8 km) and two-mile-wide (3.2 km) layer of thick, yellowish-brown mud.

Racetrack Playa lies in between two mountain ranges (a group of mountains in a line) in Death Valley – the hottest, driest, and lowest area in the U.S. Death Valley is in the Mojave Desert in eastern California, about 140 miles (~225 km) west of Las Vegas.

Nearly 100 years ago, visitors noticed that the rocks on the playa – some larger than a man – moved from time to time. One year they would be in one place and the next year in another. And when they moved, they left tracks, or trails, in the soft mud.

The rocks’ movement was rarely the same. Sometimes they moved a few inches (1 inch = 2.54 cm), other times much farther. Sometimes the tracks were straight, other times they curved or even zigzagged (moved like a “Z”) across the playa.

Many scientists have tried to explain why the rocks move the way they do. But no one has succeeded, that is, until recently.

The mystery was solved one day last December by two scientists, Richard and James Norris, according to an article in the Los Angeles Times. When they arrived at the playa, Richard said that it was covered with ice. They also noticed new rock trails near piles of broken ice along the shoreline (edge of the lake).

The next day, the two cousins were sitting nearby when they heard loud cracking (breaking) sounds from the playa. “It’s happening,” Richard yelled.

The sun had begun to melt the ice, and when the wind began to blow, the ice began to break into floes (areas of floating ice). The wind blew the floes across the lake and into the rocks. As the Norrises watched, the large, thin floes pushed the rocks so they began to slide across the slippery (wet, smooth) mud of the normally-dry lakebed (bottom of the lake).

So, what happened? What made it possible for the Norrises to see what no one had ever seen before? The answer is that they were there at the right time, when the all the conditions (things that must happen before something else can happen) were just right. What were these conditions?

First, there was water in the playa from one of the infrequent (rare; not happening often) rains or runoff (water from melted snow) from the nearby mountains. The water makes the lakebed soft and slippery. And it was deep enough for ice to float on top of it, but not deep enough to cover the rocks.

Second, the water froze enough to form what they call “windowpane” ice – ice that is thin enough to move freely (easily) on top of the water but thick enough that it doesn’t easily break.

When the ice began to melt, it broke into floes that a light (not strong) wind was able to blow across the shallow lake. When the floes moved, they pushed the rocks in front of them, and the rocks left their telltale (a sign that shows that something has happened) trails in the soft, slippery mud.

Mystery solved (to find the right explanation for something that is difficult to understand)!

~ Warren Ediger – ESL coach/tutor and creator of the Successful English web site, where you’ll find clear explanations and practical suggestions for better English.

Photo credit:

This entry was posted in Life in the United States. Bookmark the permalink.

11 Responses to The Mysterious Moving Rocks Of Racetrack Playa

  1. Peter says:

    Duh, it is obvious!
    U goona be joking.
    Does it really take scientists 100 years to figure it out. It is common knowledge that the desert gets freezing cold once night falls. and gets scolding hot during daytime . So , once there is a rain at night the accumulated water freazez over and the next morning it all melted away and runs. In the case of the aforementioned playa ,the playa is flunked by montains with presumably snow caps or sth that creates runoff. When the runoff finds its way in the dessert-like lake at night, it gets all Icey. In the mornining the ice gets Wattery abd The mud gets all slushy , ergo , the rocks slides down.
    You don’t need to be a brainiac to figure this all out. Specially , when u see the mountain and the mud.
    :))) u don’t need to get all technical on us to explain physica 101 :))))

  2. emiliano says:

    We can speculate about nearly everything but evindently that kind of thought
    has nothing to do with the real proof that one could watch in situ and these
    scientists were, as Warren said, in the right place the best moment with all
    the necessary conditions to explain the fenomenon.
    I think it is not so easy because there is a significant difference between one
    or several speculations and the real fact that proof what we are imaginated
    or speculated.

    That´s my opinion dear Peter, and of couse you are very welcome as always
    you do the necessary to start a nice controversial.

    Thank you so much dear Peter we do need you here in the blog to have just
    a little salt in it, and you put it Peter.

    Again, welcome.

    By the way where have you been boy?


  3. Dan says:

    Hi everyone.

    I read about this when it came out recently.

    Even though the UFO explanation was funnier, I just want to say thanks to this people for being so curious and willing to go out on the field to understand and seek a rational explanation for something unknown.


  4. Dan says:

    Just last week I was listening to the TED radio hour on NPR.

    It was about curiosity and discovery. Great stuff.

    For those interested, those talks are still there as a podcast. Just Google “TED radio hour”


  5. emiliano says:

    Thank you Dan, I got it, it´s interesting.

  6. Peter says:

    A peon that I m , I don’t know squat about fancy ,big words.
    I wrote what I say
    And what is say doesn’t make much sense.
    Well , I m whom I m
    Some times the post up there is mind boggling.
    They make me think.
    See , what you did Warren
    U made me think

  7. Peter says:

    Hi Emiliano ,
    How are you my dear friend
    I have been crazy busy with life.
    U know a bout a year ago , like throw a curve at me that made my life a living hell.
    Well , sh.t happens 🙂
    However, it is a thing of past
    Happy that I finally got out of it.
    I was in the pickle for a while big it is over.
    The residual is still in my system but I m getting it out of my system , flush it out if you will.
    Always good to read about you guys .
    I would lurk sometimes around the blog.
    But , I couldn’t think straight to write sth here.
    Now , that is all over . I feel the need to cyber socialize , to cyber mingle a bit.
    I bet there are a lot if new faces around the blog that I have not made acquaintance with yet.
    Bit I could track of some old friends here like you and Ben
    Hey ,
    What is the scoop with Betty?
    How is she doing ?
    Last time I checked , she was very active in this blog.
    Always good to be back
    Thanks for asking
    Very nice of you
    I admit that I stir up some emotions here or there. Well it is my nature . I always speak my mind. I m a bit rough around the ages.

  8. Warren Ediger says:

    Peter, and the rest – If you look at what’s necessary to move the rocks of Racetrack Playa like a recipe, here are the ingredients:

    1. Water from rain or runoff – rare in Death Valley (it’s the driest place in North America).
    2. Just the right depth of water – if it’s too deep or too shallow, it’s impossible to move the rocks.
    3. Just the right thickness of ice – if it’s too thin, it breaks; if it’s too thick, the wind can’t blow it across the water on the playa.
    4. Just the right amount of wind – too much wind breaks up the “window pane” ice; too little wind can’t move the rocks.

    All of these contingencies (something that must exist or happen so that something else can happen) must happen at the same time – and they rarely do – for the rocks to move. That’s why scientists have been puzzled for so many years. And that’s why the Norrises were so fortunate to be there when it happened to see it.

    Also, note that the rocks slide “across” the playa (it’s flat), not “down”. That means that the wind and ice must work against inertia (the scientific idea that something that is not moving wants to continue not moving).

  9. Dan says:

    I was virtually visiting the place with Google Earth.

    I must say that besides the moving rocks, the place alone is magnificent. I would like to see what kind of creatures live there. I guess some kind of lizard.

    There is a panoramic photo that allows you to be right there. And if I am not mistaken it right in front of the same rock shown in the pic above.

    I would also like to add that, one thing is reading an article about it, one other is actually being there and looking at a rock that you cannot even pick up, that apparently “move by itself” kind of.


  10. emiliano says:

    That´s incredible, looking the photos of a man called Raymond Coveney
    that has taken wonderful pictures of all the mountains, the stones and

    Thank you Dan, and Warren, you have gave me the idea of seaching
    with google earth…..and we could see so fascinating pictures of
    the Death Valey and the sliding stones…………wuaaaouuuu

    Thank you Warren for your explanation.


  11. Dan says:

    Me again.

    Please allow me to self mocking, self criticizing myself saying that probably those rocks move around more that what I do.

    A part from that, I saw a 26 minute video of the place posted by a guy on You Tube.
    It is not hard to find. It was posted early this year and it is one of the first result looking for Racetrack Playa.
    To me it is a good video with good commentary by the guy. The only annoying thing is that he is chewing on a gum.

    In the video it is well shown the beauty of the place. And it is not just rocks that get pushed around, there are also tree’s branches.


Comments are closed.