The fact that the speaker does not specify what, precisely, is the "Something" that "sends the frozen-ground-swell" under the fence could mean that the word something refers to nature, as another educator suggested, or even God. The word "sends" in line two implies that the sender has a will, a conscious purpose, so it seems logical to consider the possibility we should attribute such a sending to a higher being. Further, in the lines which follow the first two, this "Something" also "spills" the big rocks from the top of the fence out into the sun and "makes gaps" in the fence where two grown men can walk through, side by side (lines 3, 4). These verbs are also active, like "sends," and imply reason and purpose to the one who performs the actions. Therefore, it is plausible that the "Something" which sends "the frozen-ground-swell"—freezing the water in the ground so that the ground literally swells and bursts the fence with the movement—"spills boulders," and "makes gaps" refers to God.