Breakdown of Það flýgur örn upp úr dalnum.
það
it / there (existential) / the one (n)
fljúga
to fly
úr
out of
upp
up
Questions & Answers about Það flýgur örn upp úr dalnum.
Why does the sentence start with Það if it means 'An eagle is flying'?
This uses the existential það. In Icelandic, when the subject is a new, indefinite noun (like 'an eagle' instead of 'the eagle'), it is very common to put Það in the first position and move the real subject (örn) right after the verb. It functions a bit like 'there' in the English phrase 'There flies an eagle', but Icelandic uses it much more freely with regular action verbs.
Since Það is at the beginning, does the verb flýgur agree with Það or with örn?
The verb always agrees with the real subject, which is örn (eagle). Það is just a dummy word acting as a placeholder. Because örn is third-person singular, the verb is the third-person singular flýgur. If the subject were plural, the verb would change to match it, but the sentence would still start with Það.
Why is the word for 'valley' written as dalnum here?
The preposition úr (out of) always governs the dative case. The base word for valley is dalur. When you add the definite article to mean 'the valley', it becomes dalurinn in the nominative case, but after úr it must change to its dative form, dalnum.
Why does the sentence use both upp and úr?
Icelandic frequently combines directional adverbs like upp (up) with prepositions like úr (out of) to give a very precise, visual description of a movement. Together, they simply mean 'up out of'.