Blank Verse
Don't look at us with that blank expression. Blank verse isn't all that complicated once you know what's going on. A blank verse poem, like this one, is written in regular iambic pentameter, meaning that each line is composed of five ("penta-" means five) two-syllable pairs called iambs. The first syllable is unstressed and the second one is stressed, creating a daDUM effect. Let's pull a line from the poem to check it out:
This wizened earth has never troubled us. (3)
Hear the daDUM daDUM daDUM pattern? Those are iambs at work. Each iamb, in turn, is known as a "foot." Five of these feet in one line makes for a total of—wait for it—ten syllables in each line.
As for the "blank" part, this just means that the lines aren't rhymed. So, while many poems rely on rhyme to create a sense of organization, this one creates its flow from the consistent syllabic rhythm within the line.
As you can tell, blank verse is a very subtle form of poetry. Since there is no rhyme, there is nothing to really announce that this is a formal poem. Iambic pentameter doesn't exactly jump out at you either; it's supposed to mimic the most natural cadence (rise and fall) of English speech.
Heaney also uses other poetic forms, like enjambment, to keep the rhythm of the poem moving along steadily. When he chooses to break a line (like with line 16: "while the wind dives/ And strafes"), he's choosing to keep the poem moving, rather than fully stopping with some sort of punctuation at the end of every line. That kind of end stop would be pretty disruptive. The goal of blank verse is to keep everything tied together and running smoothly (so we don't have any super-short, choppy lines followed by long, rambling ones), and we think Heaney achieves just that in "Storm on the Island."
But why go this route? What is it about blank verse that makes Heaney apply it in this poem? Well, as we said, it creates a kind of conversational rhythm, which adds to the effect of the speaker's informal commentary on life on his island. More importantly, though, it creates a kind of regular, peaceful structure—almost like a stone house—that might survive the kind of violent storm that the poem describes. So, is Heaney saying that the only true refuge from the natural world is in poetry? We wouldn't necessarily disagree with him if he were.