Word groups that are also considered to be adverbials can also modify verbs: for example, a prepositional phrase, a noun phrase, a finite clause or a non-finite clause.
Another aspect of "it" -extraposition that distinguishes it from canonical cases is that the extraposed constituent is usually a clause; "it" -extraposition can not extrapose a prepositional phrase.
In some contexts the same can be expressed by a prepositional phrase, as in "the twin curses of famine and pestilence" (meaning the twin curses that are famine and pestilence).
