AAPT Logo
AJP Logo
 
   
 

You are not logged in You are not logged into this journal. Log In

American Journal of Physics -- January 2011 -- Volume 79, Issue 1, pp. 37

Ice rafts not sails: Floating the rocks at Racetrack Playa

Ralph D. Lorenz1, Brian K. Jackson2, Jason W. Barnes3, Joe Spitale4, and John M. Keller5

1Applied Physics Laboratory, Johns Hopkins University, Laurel, Maryland 20723
2NASA Goddard Spaceflight Center, Greenbelt, Maryland 20771
3Department of Physics, University of Idaho, Moscow, Idaho 83844
4Space Science Institute, Boulder, Colorado 80301
5Department of Physics, California Polytechnic State University, San Luis Obispo, California 93407

Full Text: Read Online (HTML) | Download PDF | Rent Article () | Buy PDF (US$30) | View Cart
We suggest 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, as also occurs in arctic tidal beaches to form boulder barricades. 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. We demonstrate the effect with a simple experiment.

© 2011 American Association of Physics Teachers

ACKNOWLEDGMENTS

One of the authors (B.K.J.) acknowledges the assistance of a grant from the Geological Society of America and support from the Director of the Lunar and Planetary Laboratory, University of Arizona. Another one of the authors (R.L.) acknowledges the support of the NASA Cassini project and the Applied Information Systems Research Program. The authors appreciate the interest of David Ek, the Wilderness Coordinator at Death Valley National Park in this work. They acknowledge the assistance of Zibi Turtle, David Choi, Catherine Neish, Lizza Demsetz, Anita Milman, Rebecca Rosen, and Ryan Silva. They also acknowledge interesting discussions about the playa with Jay Melosh, Alex Hayes, Jani Radebaugh, and Paula Messina. They thank an anonymous referee for comments

Article Outline

  1. INTRODUCTION
  2. MECHANICS OF RAFTED ROCK MOVEMENT
  3. SOME EXPERIMENTAL SUPPORT FOR THE RAFTING MECHANISM
  4. DO ROCKS ACTUALLY FLOAT AND DOES THE PLAYA ACTUALLY FREEZE?
  5. CONCLUSIONS

KEYWORDS and PACS

Keywords

ice, physics education, rocks, teaching, wind

PACS

  • 47.00.00

    Fluid dynamics

  • 93.00.00

    Geophysical observations, instrumentation, and techniques

RELATED DATABASES

To view database links for this article, you need to log in.
History
Received Feb 2010
Accepted Aug 2010

PUBLICATION DATA

ISSN

0002-9505 (print)  

Publisher

$abstract.society.value is a Member of CrossRef American Association of Physics Teachers

ARTICLE DATA

Digital Object Identifier
http://dx.doi.org/10.1119/1.3490645

For access to fully linked references, you need to log in.

Figures (10)

Access to article objects (figures, tables, multimedia) requires a subscription; log in to view available files.
(Access to supplementary files, where available, is free for this journal.)



Close

Your Recent History Recent History Help

Recently Viewed

  1. Ice rafts not sails: Floating the rocks at Racetrack Playa

AAPT on:

close