What Really Drives Death Valley’s Roving Rocks?

The moving, sailing and sliding rocks of Racetrack Playa, Death Valley National Park in California have garnered the attention of many scientists and visitors throughout the years. The Racetrack Playa is a dry lake featuring the race track imprints of the moving rocks. The moving rocks are a geological phenomenon where the rocks, some weighing about 318 kgs, move without any human intervention.

roving-rock
Photograph by Pete Ryan

There have been many theories regarding the motion of these rocks. Research on this phenomenon started as early as 1915 when theories suggested that the wind had a role to play in moving the rocks. However, with some stones weighing 318 kgs, it is not probable for the wind to move them. Therefore this theory was discarded. In 1955, George Stanley, a geologist did extensive research on the phenomenon and stated the theory that ice sheets around the rocks help to catch the wind, initiating the movement. His theory again stressed that wind plays a role in the rocks’ movement.

Credit: Maggie McAdam

Further research was done in the 1970s by Bob Sharp and Dwight Carey where they monitored the rock movement by naming the rocks and keeping a record of their changing positions over a period of seven months.

The research continued in the 1990s by the research students of Hampshire College and the University of Massachusetts Amherst. The movement of the stones was evident to be the result of two factors: wind and ice floes. In 1996 it was discovered that the wind blowing on the Playa could be intensified and compressed due to its smooth surface and the wind gusts initiate the movement while the moment keeps them moving.

Ice and Wind

In 2006, Ralph Lorenz, a NASA Scientist, investigating the weather conditions on other planets started researching on the moving rocks. Lorenz compared the meteorological conditions of the Racetrack Playa, Death Valley to those near Ontario Laucus, a vast hydrocarbon lake on Titan, a moon of Saturn.

Lorenz conducted a simple experiment where he placed a small rock in a Tupperware filled with water so that there was an inch of water with a bit of the rock sticking out. Next, he froze the Tupperware so that there was a small slab of ice with a rock embedded in it. He then placed the ice bound rock in a container of water with sand at he bottom. In order to move the rock across the water, he just gently blew on the rock and it slid. As the rock moved, it imprinted a track in the sand.

Ralph Lorenz’s home experiment
Ralph Lorenz’s home experiment

Research in 2011 established that the existence of many of the rock-carved trails at Racetrack Playa in Death Valley National Park is predominantly due to the effect of arbitrarily weak winds on rocks that are floated off the soft bed by small rafts of ice, the ‘ice raft theory’.

Credit: Anatoliy Lukich
Credit: Anatoliy Lukich

These ice cakes need not have a particularly large surface area if the ice is adequately thick-the ice cakes allow the rocks to move by buoyantly reducing the reaction and friction forces at the bed, not by increasing the wind drag. The parameter space of ice thickness and extent versus rock size for flotation is calculated and found to be reasonable. Lorenz’s experiment illustrated this ‘ice raft theory’. Therefore, wind and ice were both the favoring theories responsible for the phenomenon.

10 Quick Facts about Our Earth and the Solar System That Will Make You Wonder

1. Russia is bigger than Pluto

That’s right, the surface area of Russia, 17 million sq. km, is greater than that of Pluto, 16.6 million sq. km. (Tweet this fact!)

Pluto vs Russia
Image credits: omg-facts.com

2. The True Size of Africa

Africa is much bigger than what it looks like on most maps of the world. To put it into perspective, we can fit all of the following 18 countries into Africa and still have room for more:

USA, China, India, France, Spain, Germany, Italy, Greece, Sweden, Norway, United Kingdom, New Zealand, Japan, Mexico, Peru, Nepal, Bangladesh and Papua New Guinea.

The combined area of these counties is 30.1 million sq. km which is still slightly less than that of Africa. [See map]

3. Okay, Oklahoma

There’s a town called Okay, OK. It has a population of about 650. (Tweet this fact!)

okay-ok

4. Only 2 percent of the Australian population lives in the yellow area

The total area of Australia is almost equal to that of United States minus Alaska, however, its (Australia’s) population is just 23 million which is less than the population of Texas alone.

australia_population

5. Since its discovery, Pluto never made a full orbit around the Sun

pluto_orbit

Pluto takes 248 years to complete its orbit around the sun that our earth completes is just one year.

6. The Diomede Islands are 2.4 miles and One Day apart

Diomede Islands, Bering Sea

The Diomede Islands, just 2.4 miles apart are separated by International Date Line. They are also named “Tomorrow Island” and “Yesterday Island”. Big Diomede belongs to Russia and has a population of zero while the Little one belongs to United States with a population of about 200. Since the big Diomede belongs to Russia, it’s 23 hours ahead of the little Diomede.

date_line

You are seeing the map right! Russia and Alaska are indeed this close apart. This is the part where we cut the world map to present it in a planer form instead of a globe.

7. You can actually fly on Saturn’s moon Titan

The gravity is low enough and the atmosphere thick enough on Titan, that by attaching small wings to your arms, you could fly like a bird. The gravitational pull there is seven times less and the escape velocity is four times less than that of the earth.

human_wings

8. If an alien located 60-65 million light years away from us, looked at earth through a really powerful telescope today, he would see Dinosaurs!

dinosaurs

This makes sense since we, at earth, are only able to see the objects in the outer space who’s light has reached us. The Dinosaurs lived on this planet about 60-65 million years ago and their light/visibility has only reached the location 60-65 million light years (or 382,102 trillion miles) away yet. [via quora]

9. The World’s population can fit comfortably in Texas

The world with a population of 7 billion can fit easily in Texas –Tweet this– (water included in area) with each person having a 1000 sq. foot property of his own. Of course, there’ll be no space for roads, parks and other infrastructure whatsoever. [image courtesy: aliveandyoung]

texas_world

10. A day (sunrise to sunrise) on Mercury is 176 Earth days

Unlike earth, the planet Mercury rotates very slow about its own axis taking almost 59 of our days to complete one rotation. That’s one day by Mercury’s definition, however, one solar day (sunrise to sunrise) on Mercury, which depends on both its rotation and orbital motion around the sun, is 176 Earth days.

mercury_sun

Mercury completes its orbit around the sun in approx 88 days so it’s daytime for one Mercurian year, and night-time for another Mercurian year. To complicated to understand? Watch the simple animation. You’ll notice that the Mercury completes its orbit around the sun during the time from its sunrise to sunset. And while the sun rises back from the sunset, it complete yet another orbit around the sun. So from sunrise to the next sunrise, Mercury orbits around the sun twice i.e. 176 days.