It could be either:
The hours after the hike were mostly spent recuperating. (adjective)
The scoutmaster talked to the boys after the hike. (adverb)
If the phrase describes (modifies) a noun or pronoun, it's an adjective phrase. If the phrase describes a verb, adjective, or adverb, it's an adverb phrase.
an adjective phrase acts like an adjective and modifies the noun or pronoun in the sentence. an adverb phrase acts like an adverb and modifies the verb, adjective, or adverb in the sentence.
Adverb Phrase
adverb phrase
It is an adverb phrase (tells where).
adjective phrase
adverb
adverb phrase
adverb phrase
It is an adverb phrase, although in forms such as "The period after a supernova is marked by stellar collapse" it seems to be an adjective phrase.
This is a sentence (or clause), not a phrase. The adjective is dumb, and the adverb is very, modifying dumb. So "very dumb" is the adjective phrase.
Yes, prepositional phrases can function as either adjective phrases or adverb phrases in a sentence. An adjective phrase modifies a noun or pronoun, while an adverb phrase modifies a verb, adjective, or adverb.