Hummocky cross-stratification

[1] In plan view (seen from above), it takes on the form of hummocks and swales that are circular to elliptical, with long wavelengths (1–5 m) but with low height (tens of centimeters).

This structure is formed under a combination of unidirectional and oscillatory flow that is generated by relatively large storm waves in the ocean.

As the large waves drape sand over an irregular scoured surface, this strong storm-wave action erodes the seabed into low hummocks and swales that lack any significant orientation.

[2] During ancient times, hummocky cross-stratification was located in shallow marine environments, on the shore face and shelf by waves.

These landward deposits feature smaller bed forms due to the attenuation of storm waves as they move onto the land.