Dendritic ridges self-organize on an undercut barchan dune slip face

Dendritic ridges

I came across a beautiful barchan sand dune at Ocean Beach in San Francisco after a very windy period.

Diagram of a barchan sand dune

The slip face of the dune, being at its angle of repose, had formed a gorgeous slump — a most successful failure! — which can be seen left of center in the first photo below.

After photographing the slump, I began to experiment with slightly undercutting small portions of the base of the barchan dune slip face.

This would cause sand to avalanche from the upper edge of the disturbance, producing a mesmerizing effect: gullies such as in the lower center would slowly migrate to the top of the slip face, as can be seen to the left and right.

When the sand settled, often taking many minutes, dendritic ridges remained.

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Puako Petroglyphs – Pictures of plasma formations in the sky?

The Puako Petroglyph field on the Big Island of Hawaii is covered with rock carvings by ancient Hawaiians.

The meanings of these enigmatic symbols, as with most of the Hawaiian petroglyphs, have eluded archeologists.

Perhaps the Hawaiians were carving into the rock their most realistic attempts at documenting awe-inspiring plasma formations — extremely powerful aurorae with high geometric symmetry — that filled their sky.

I have a thread at the Thunderbolts Forum, a site exploring counter-theories to the standard models of modern astronomy and cosmology, that is dedicated to the Puako Petroglyphs, which I had the thrill of seeing as a child living on the Big Island.

Puako Petroglyphs — EU’s a Beach on the Big Island of Hawaii, by Max Photon