Breakdown of Það hreyfist lítill refur í hrauninu.
það
it / there (existential) / the one (n)
lítill
small / a little (small amount)
í
in / into / to (before the hour, in telling time) / per (in frequency expressions)
refurinn
the fox
Questions & Answers about Það hreyfist lítill refur í hrauninu.
Why does the sentence start with Það when the English translation is just "A small fox..."?
This is the existential það, which works a bit like "there" in English. Icelandic uses it to introduce a new, indefinite subject into a scene. If translated literally, it would be "There moves a small fox in the lava." By placing það in the first position, the real subject (lítill refur) is pushed after the verb.
Why is the subject lítill refur placed after the verb instead of at the beginning?
This is the main rule of existential það sentences: the "dummy" subject það takes the first position, keeping the verb in the second position, and pushing the actual subject into the third position. Remember that you can only do this when the subject is indefinite (a fox, not the fox).
Why does the verb end in -st (hreyfist)?
This is the middle voice form of the verb hreyfa (to move). While the active verb hreyfa means to move something else (like moving a chair), the -st ending changes it to hreyfast, meaning the subject is moving itself. Here, the fox is moving its own body.
Why is hrauninu in the dative case after the preposition í?
The preposition í takes the dative case when describing a fixed location where an action is taking place. Because the fox is moving around inside the lava field, rather than entering it from the outside, the dative form is used.