This is the elevated section of the beach bike path that goes along the berm where they do the hang gliding lessons (it's at the end of this picture, about 100 yards down from where the picture was taken).
It's been very windy the last 4 to 5 days.
The wind has blown sand on the bike path...
Most of it is traversable with the bike but it's not good for the bike to have the sand get into all the moving parts, especially the chain and gears.
Using a dry lube helps quite a bit with this issue (wet lube and sand don't mix...).