A jar of white river silt

What would you tell me, if only you could, how you came to be here in this jar ?
you were free in the river once, that much I know, it's waters had brought you so far

you were born in the mountains, I think, where the weather and rocks battle still,
worn down by millennium's winters, carried off when the melt waters spill

your sibling sand, pebbles and gravel, they settled upstream far away
but you were too fine to settle, till the river. and you, came this way

then came nineteen twenty six when that river slipped under the door
then it slithered away, and left you here, in a layer across the floor

and who knows why they kept you, were they keeping the great flood in mind ?
just a jar of fine silt kept for 93 years when the white river left you behind