The poem begins by looking far back, to a time when meltwater rivers laid down gravel and sand along the sides of mountains, leaving the flat shelves the title calls kame terraces. The speaker pictures the scene: a valley still choked with ice, and a wild rush of water across from it. Then the view shifts to the present, to the woods that grow there now. Three kinds of oak, witch hazel, and teaberry cover land that was logged but never plowed, so it still carries traces of its long past.
The short couplet in the middle, "So much time, / yet not enough time," is where the speaker's feeling comes through. Geological time makes a human life seem tiny, yet that life still feels too short. The ending turns this into a wish. The speaker wants to be like the river at the ice's edge, letting go where possible and holding on where necessary. The mood is quiet, reflective, and gently accepting, with a little ache underneath.