Erosion instabilities

Everywhere in nature erosion is sculpting the landscape. As soon as an erodible sediment is in presence of a fluid flow (wind, waves, currents,...) , very diverse structures can appear, at various scales.The structures illustrated below are all classical subjects of geomorphological studies. All of them originate from the transport of solid grains by the fluid, and obey to the same general mechanisms as the sand ripples.

Aeolian sand ripples (Mauritania)	Sand dunes (Brazil)
Alternate sand bars in a river (Japan)	Instability of the shoreline (Azov Sea)
Meandering river (USA)	Braided river (Iceland)