Relationship between temporal/adverbial nouns modified by relative clauses with verbs


I came across with the following sentence:

> 受験勉強で疲弊した **深夜** 、グレープフルーツのへそに親指を挿入した **瞬間** 、胸からぷしゅっと黄色の粒子が **噴出** した。

I was doubtful about how the sentences separated by commas were related to
each other, so I asked a Japanese person to help me out. She said the nouns 深夜
and 瞬間 were both functioning as adverbs. She also added that the particle に
could be placed after these two nouns and the meaning would be the same, even
though it would make it more casual instead of the current literary version.

However, I still have a question. If these nouns are actually working as
adverbs, that is, temporal nouns, what verb specifically were they actually
modifying? After trying to answer it for myself, I ended up with three
possibilities, but I can't say which is correct.

  1. They are modifying the next verb. 挿入する for 深夜, and 噴出する for 瞬間.
  2. Both are modifying the last verb, 噴出する.
  3. They are actually independent sentences, that is, the 深夜's sentence is a sentence separated from the remaining and the same applies to 瞬間. And if that's the case, how could they be adverbs?

This sentence structure seems to be quite frequent, and I always get confused
with it.

Note that this question about [Adverbial Nouns and Temporal
Nouns](https://japanese.stackexchange.com/questions/23406/adverbial-nouns-and-
temporal-nouns) has nothing to do with mine.




To me it looks like there are two adverbial clauses, both "modifying" the
final verb 噴出した by specifying **when** that act happened. So the verb phrases
that come before 深夜 and 瞬間 are just modifying the respective temporal noun,
turning each comma separated section into a clause.

[受験勉強で疲弊した深夜]、[グレープフルーツのへそに親指を挿入した瞬間]、胸からぷしゅっと黄色の粒子が噴出した。

Notice that each bracketed section is not a sentence in itself as it doesn't
end in a verb, copula, etc. They are simply nouns with descriptors attached.
That rules out #3. As for the difference between 1 and 2, since these are all
describing essentially one moment - when yellow particles spurt out of a
grapefruit - I guess the sentence may also be broken up as:

{[受験勉強で疲弊した深夜]、グレープフルーツのへそに親指を挿入した瞬間}、胸からぷしゅっと黄色の粒子が噴出した。

But to me those seem like they have essentially the same meaning, but the
first breakdown seems more natural to me due to the parallel structure between
the two clauses.

A simpler example of this same structure may be something like:

「 **昨日** 、 **朝** 、りんごを食べました」

Both nouns are describing when the eating happened. They are acting as adverbs
by modifying the last verb.




To me it looks like there are two adverbial clauses, both "modifying" the
final verb 噴出した by specifying **when** that act happened. So the verb phrases
that come before 深夜 and 瞬間 are just modifying the respective temporal noun,
turning each comma separated section into a clause.

[受験勉強で疲弊した深夜]、[グレープフルーツのへそに親指を挿入した瞬間]、胸からぷしゅっと黄色の粒子が噴出した。

Notice that each bracketed section is not a sentence in itself as it doesn't
end in a verb, copula, etc. They are simply nouns with descriptors attached.
That rules out #3. As for the difference between 1 and 2, since these are all
describing essentially one moment - when yellow particles spurt out of a
grapefruit - I guess the sentence may also be broken up as:

{[受験勉強で疲弊した深夜]、グレープフルーツのへそに親指を挿入した瞬間}、胸からぷしゅっと黄色の粒子が噴出した。

But to me those seem like they have essentially the same meaning, but the
first breakdown seems more natural to me due to the parallel structure between
the two clauses.

A simpler example of this same structure may be something like:

「 **昨日** 、 **朝** 、りんごを食べました」

Both nouns are describing when the eating happened. They are acting as adverbs
by modifying the last verb.

