Have you ever noticed that when you walk on a wet sandy beach near the water a peculiar effect occurs? The sand changes its character in a most interesting way. This question uses the beach model photographed below to find out what happens when you walk on a wet beach just after a wave has washed up and left.
The question involves exactly what is happening when you step on beach sand that is saturated with water. In particular, does the sand around your foot become wetter, dryer, or stay about the same when your foot is exerting pressure on the beach. It might get wetter if your foot pushes the sand particles together and forces up some of the water in the sand. It might get dryer if your foot pushes some of the water down into the sand below it. Or it might stay about the same, because it started out saturated with water anyway.
Notice that in the close-up of the beach sand in the photograph at the right you can see a bit of water lying on the surface, so the sand is somewhat saturated. The experiment involves stepping on that sandy beach with your foot - shown in the larger photograph at the left.
When you step on a water-saturated sandy beach, the area around your foot:
Click here for Answer #171 after January 19, 2004.
