The Mystery of the Sailing stones
“Sailing stones” rest at the far end of a smooth track on a dry lakebed. How they get there has baffled observers for at least a century. No one has ever seen the rocks move, but scientists are getting closer to figuring out how they do it.
How Do the Rocks Move?
Many observations have been made over the years:
- The rocks have very different sizes. Many are 1 to 2 lbs, many are as large as 20 to 30 lbs. Amazingly, one is estimated to be 700 lbs!
- Stones may move short distances, but one moved more than 600 feet in one winter!
- Stone sliding is seasonal: the rocks do not move in summer, but they do not move every winter.
- The tracks may change directions. Big rocks may move farther than small rocks, but not always.
Over the decades many hypotheses have been proposed, including the following. Do the rocks move
- by sliding downhill?
- by people or animals?
- during an earthquake?
- from magnetic attraction?
- by strong winds?
- in an ice floe?
Read the following article to learn more about the racing rocks of Racetrack Playa in Death Valley National Park. Then answer the following questions.
- The Mysterious Roving Rocks of Racetrack Playa: http://www.nasa.gov/topics/earth/features/roving-rocks.html
- Hypotheses 1, 2, 3 and 4 above were discounted easily. How would you test each one of these?
- What must happen for wind to be able to move such large rocks?
- What is the current hypothesis to explain how the racing rocks move?
- What technological devices are now being used to study the racing rocks and what do they do?