Transverse instability of megaripples

Mar 20, 2012

Aeolian ripples, which form regular patterns on sand beaches and desert floors, indicate the fundamental instability of flat sand surfaces under the wind-induced transport of sand grains.

Two kinds of sand ripples exist: normal, small ripples and megaripples with wavelengths reaching up to several meters. They differ also in their grain-size distributions (unimodal for sand ripples and bimodal for megaripples).

While sand ripples form almost straight lines, megaripples have greater sinuosity due to their transverse instability, a property that causes small megaripple undulations to grow with time.

The origin of the instability is due to variations in megaripple height, which do not diminish over time, as well as to the inverse dependence of ripple drift velocity on height. Thus, the taller regions of ripples will move more slowly than the adjacent, shorter portions, an outcome that promotes further perturbation growth.

Hezi Yizhaq of Ben-Gurion University of the Negev and colleagues provide an example, based on field work, of the transverse instability of megaripples. The instability growth rate depends on the difference between the heights of the different segments of the megaripple.

Their results suggest a for the transverse instability of megaripples and new insight into the spatial patterns of .

Explore further: NASA sees western edge of Tropical Storm Fung-Wong affecting Philippines

More information: Hezi Yizhaq et al., Geology, Posted online 19 Mar. 2012; doi: 10.1130/G32995.1

Journal reference: Geology search and more info website

Provided by Geological Society of America

5 /5 (1 vote)
add to favorites email to friend print save as pdf

Related Stories

Scientists explore the physics of bumpy roads

Jul 07, 2009

sand or gravel or snow -- develops ripples that make driving a very shaky experience. A team of physicists from Canada, France and the United Kingdom have recreated this "washboard" phenomenon in the lab with ...

Mars Dunes: On the Move?

Mar 04, 2010

(PhysOrg.com) -- New studies of ripples and dunes shaped by the winds on Mars testify to variability on that planet, identifying at least one place where ripples are actively migrating and another where the ...

First images of flowing nano ripples

Mar 21, 2006

Delft University of Technology (Holland) researchers have shed new light on the formation of nanoscale surface features, such as nano ripples. These features are important because they could be useful as templates ...

Image: Blue on Mars

Feb 17, 2011

This image shows part of the floor of Rabe Crater, a large impact crater in Mars' southern highlands.

Recommended for you

Tree rings and arroyos

9 hours ago

A new GSA Bulletin study uses tree rings to document arroyo evolution along the lower Rio Puerco and Chaco Wash in northern New Mexico, USA. By determining burial dates in tree rings from salt cedar and wi ...

NASA image: Agricultural fires in the Ukraine

10 hours ago

Numerous fires (marked with red dots) are burning in Eastern Europe, likely as a result of regional agricultural practices. The body of water at the lower left of this true-color Moderate Resolution Imaging ...

NASA marks Polo for a hurricane

11 hours ago

Hurricane Polo still appears rounded in imagery from NOAA's GOES-West satellite, but forecasters at the National Hurricane Center expect that to change.

User comments : 0