"Power" is written in free verse, which means that it doesn't have a stable rhyme scheme or meter. But the poem does have one formal element that really jumps out: it's got an odd pattern of spacing, especially at its beginning and end. Remember the first five lines of the poem?
Living in the earth deposits of our history
Today a backhoe divulged out of a crumbling flank of earth
one bottle amber perfect a hundred-year-old
cure for fever or melancholy a tonic
for living on this earth in the winters of this climate
There are extra-long spaces all over the place. They make the poem seem really fragmented and disjointed, because we see literal absences everywhere. These absences raise a whole lot of questions for us. What is the speaker leaving out? What information is missing from these stories? Why so wonky?
While the number of these absences decrease in the poem's middle, they come back with a vengeance (and also, with a whole lot of enjambments) at the end of the poem. More blank spaces, more fragmented writing. As we hear of Curie's body falling apart, the words on the page begin to literally fall away from each other ("the cracked and suppurating skin of her finger-ends / till she could no longer hold a test-tube or pencil"). More spaces mean more fragmentation, both on the page, and in Marie's life.
Rich uses this unique formal technique—making absences present on the page—a key part of her free verse form. Still, this technique opens up a whole lot of questions, rather than tying up answers in a neat little bow for us.