Tuesday Tea Time Poem

On Tuesdays after lunch, we eat treats and read poems aloud to each other. Mostly, we select poems in anthologies to share. The three year old chose a math poem, "Gazintas" every week for about six months straight. Today, Praise God From Whom All Blessings Flow, he finally moved on to a new selection. Occasionally, one of the kids will choose to write an original poem rather than select one from our various books.

Eldest son wrote this today--thought you all might enjoy it:

Endless motion
Never frozen
Defining life
Bringing death
Forming mountain
Creating town
Only to bring them crumbling down
Resolute, marching on
Bringing both night and the dawn.

What am I?