Upon the ocean shore,
   there is a rock:
   hard,
   black,
   porous,
   volcanic.

Gentle seas send ripples
   against its base.

Stormy seas send waves
   to relentlessly batter it,
   crashing over its top.

Both the lapping waves
   and the crashing waves
   cart away parts of the rock --
   one unit of grit at a time.

The lapping waves need patience;
  the crashing waves need energy,
    but they both insist a tax be paid
     for their labors.

Just looking at the rock,
 one can tell it was once different:
    bigger,
    its pores filled
        with other rock -- softer rock,
  rock that the sea long ago turned
    into sandy bottoms and beaches.

The rock is dissolving like an ice cube,
  except in geologic time.