With irregular pits and strips of loose sand. Even the 38s sink in more than an inch. You can see a patch of it with deep ruts in picture 2.

Oh, and the cobble. The whole area that is not packed sand/clay mix is tailings piles left over from the Gold Rush, or fist sized cobbles.... several layers deep. They shift like you would not believe.

I will take some pictures of the washouts and sand pits next time I am out.

Here is the sort of cobble you run into. The trail will just fade out into this. That dirt is only a few inches thick, the river rising significantly will wash it right out and the cobble is exposed.