I traveled to Costa Rica over the Thanksgiving holiday, and enjoyed exploring the coastal outcrops near Esterillos in Puntarenas province. Before I get to the rocks, though, I thought I’d share a bit of the patterns on the sand on the beach. These ripples, for instance:

They’re as large as pythons!

And in this set, large antidunes are bedecked in a smaller surficial “skin” of oscillation ripples:

I didn’t include a sense of scale in either of these ripple photos because I just found them so strikingly pretty, and didn’t want to mar the beauty by sticking any science in there.

At another location, at low tide, the land was seeping groundwater out through the beach, resulting in a neat ‘braided’ pattern made plain by the high contrast between biogenic particles and the volcaniclastic bulk of the sediment. Check it out – this view is looking “upstream” but I’m not sure there’s anything diagnostic here to show that for sure.

I love stuff like this; I spent a lot of quality time watching standing waves move upstream (antidunes migrating) and neat little mini-deltas forming and being eroded, endless adjustments of little bits of the Earth system under the influence of moving water.