Kelvin Helmholtz instabilities form when two layers meet with different speed or density. This mechanism can produce remarkable waveforms visible from far away.
The wave structures were first recognized in clouds and aircraft condensation trails.
Kelvin-Helmholtz instabilities are also observed at a larger scale on Earth in the ionospheric northern lights (aurora borealis).
And farther away in the solar system, Kelvin-Helmholtz instabilities are clearly visible in the cloud belt system of giant gas planet Jupiter.
Sand barrier islands
The Frisian islands are sandy barrier islands on the northern coast of The Netherlands (Waddeneilanden) and Germany (Watteninseln).They formed eight thousand years ago when sea levels started rising as the last ice ended.
The islands are sculpted from the enormous amounts of sand that were deposited in the Northsea by old rivers and glaciers (90%) and new local rivers (10%).
A thorough background paper on Kelvin-Helmholtz instabilities was published in 2007 by Lew Grammar (NOAA).
http://www.rsmas.miami.edu/users/isavelyev/GFD-2/KH-I.pdf
A nice timelapse video of pulsating aurora can be watched at
https://www.youtube.com/watch?v=9fIZHZ9EC1g
http://www.waddenacademie.nl/fileadmin/inhoud/pdf/04bibliotheek/Themanummer_OCMA/4_Barrier_island_management_Lessons_from_the_past_and_directions_for_the_future_OCMA.pdf
