Why do stones on the beach gather in like sized piles?

Question

Walking on the beach today I noticed that the piles of stones seem to gather in patches of similar sizes. Pea size, grain of wheat size and sand size in patches the size of a swimming pool or two. Any idea why they congregate like this?

Answer 1

The process is called "sorting" by geologists. Currents and waves move material according to the energy in the currents and waves. When the energy becomes too low to move a particle it, and all others of similar size, are deposited. Hence, pebbles, sand grains, and so on, of similar size are deposited in close proximity. In a stream, the headwaters usually have high energy and can move boulders (as well as cobbles, pebbles, sand, silt, and clay-sized particles), but, as the stream approaches the sea or a lake (called the 'base level') and it's energy decreases (the slope of the stream usually decreases toward the sea) first boulders, then cobbles, then pebbles, then sand, then silt, and finally clay-size particles are too large for the stream to carry and they are deposited. The same holds true for waves in the ocean, as far as energy versus particle size being moved and deposited.

Answer 2

This is known as retrimming resource designing. A set of
interactions include, weather, gravity, tilt for evaporation, grain
of gravity over size, and terrace movement of source material.
These are what could be called traditional average coverage.

Answer 3

The larger pebbles are heavier, therefore harder to move. The fine sand moves all the time with the wave action.

Answer 4

Maybe because they love each other.
Maybe because their resistance to the water and rolling on the sand is similar.
Maybe it is another example of organization of matter from Chaos...

Answer 5

They are at the edge of the wave action,lightest go further.