The earths plates drifted apart to be the 7 continents.
You can take an ethical, sociological and biographical approach to this piece. To look at this poem in the best detail possible, my opinion would be to use the biographical approach which tells us of the author's life, motivations for the poem, unconscious desires, and fears. For a broader focus, a sociological approach would be sufficient. We can note the differences and similarities in this poem and others.
Some salt is added
some salt is more than one so it's represented by "is"
