Enjambment, grammatical shift, and personification in Matthew Olzmann's "Letter to a Bridge Made of Rope"

In Matthew Olzmann's "Letter to a Bridge Made of Rope", the speaker is crossing a gorge on the titular bridge: "One foot set in front of the other, while the wind / rattles the cage of the living and the rocks down there [...]." As that line ends, the rocks, whether parallel to "the living" or "the cage", are "rattled" by the wind. But after the linebreak, the rocks shift grammatically from object to subject: "[...] the rocks down there / cheer every wobble [...]." With this enjambment, then, the rocks go from physical objects in the scene to the expectant personification of the danger the person crossing the bridge faces. (Andrew Shields, #111words, 9 August 2021)