I am the rocky river bed(C)

Stone:
Fixed
In appearance
Yet changing
Every little grain of sand
Rubbed off
Takes off more
Rough edges rounded off
Granite mountains to pebbles
Inexorably etched
Every memory of flowing water
Malleable, fluid
Unchanging
Yet dissolving me
Bit by little bit
Marking, striating
Deposits
Silted over,
Layer after layer
The core untouched
Of Fire
Pulsating
Pushing forcing
Wanting to melt and dissolve
Changing, reshaping

Still
Destined to be left alone
Fated to be called unyielding.