There are two questions raised about Rev 8:7, one textual and the the other interpretive. Let us address these one at a time.
The text as per NA28/UBS5, Byzantine, Majority text is as follows (my literal translation in all cases):
Καὶ ὁ πρῶτος ἐσάλπισεν· καὶ ἐγένετο χάλαζα καὶ πῦρ μεμιγμένα ἐν
αἵματι, καὶ ἐβλήθη εἰς τὴν γῆν· καὶ τὸ τρίτον τῆς γῆς κατεκάη, καὶ τὸ
τρίτον τῶν δένδρων κατεκάη, καὶ πᾶς χόρτος χλωρὸς κατεκάη.
= And the first trumpeted; and came hail and fire having been mixed
with blood was thrown to the earth. And a third of the earth was
burned and the third of the trees were burned and all the green grass
By contrast, the Textus Receptus, TR, is alone in having the following text:
Καὶ ὁ πρῶτος ἄγγελος ἐσάλπισε, καὶ ἐγένετο χάλαζα καὶ πῦρ μεμιγμένα
αἵματι, καὶ ἐβλήθη εἰς τὴν γῆν· καὶ τὸ τρίτον τῶν δένδρων κατεκάη, καὶ
πᾶς χόρτος χλωρὸς κατεκάη.
= And the first angel trumpeted, and came hail and fire having been
mixed with blood, and it was thrown to the earth; and the third of the
trees were burned, and all the green grass was burned.
The TR is almost unsupported among the MSS at this point.
To understand the highly symbolic text, we need to understand the symbols. This will vary very greatly between different schools of Prophetic/Apocalyptic systems such as Furturism, Preterism, Historicism, Spiritualistic, etc. For example,
- Futurism begins with the premise (at least most schools of futurism) that all these passages must be interpreted strictly literally
- Preterism believes that these passages all describe events that occurred in the first century
- Historicism believes that these events were fulfilled during the Christian era and culminating in Jesus return
- Spiritualist schools or prophetic interpretation look for more general ideas about the maturing of personal spiritual growth in Christians.
The above is not an exhaustive list. However, if one wishes to understand this language symbolically, then we have the following precedents:
- Trees[Gr: dendron] (4) 7:1, 3, 8:7, 9:4 - a symbol of people generally, and righteous people particularly. This is consistent with New Testament usage of tree to represent people and their character (Matt 7:17, 18, 12:33, Luke 6:43, 44, 13:19, etc.)
- Hail [Gr: chalaza] (4) 8:7, 11:19, 16:21(x2). These are the only occurrences of this word in the New Testament. However, the Old Testament has several instances of hail such as the plague of hail on Egypt (Ex 9:18-34, Ps 78:47, 48, 105:32, 33), during a battle of the Israelites with the Amorites (Josh 10:11, see also Psa 18:12-14), God’s reserves for judgement in the last day (Job 38:22, 23), as an instrument of judgement generally (Ps 147:17, 148:8, Isa 28:2, 17, 30:30, 32:17, Eze 13:11, 13, 38:22, Hag 2:17). Thus, hail is a consistent symbol of God’s judgement.
- Blood [Gr: aima] (19) Several sources of blood are used: of the lamb (1:5, 5:9, 7:14, 12:11, 19:13), of martyred saints (6:10, 16:6, 17:6, 18:24, 19:2), from heaven in a plague (8:7, 8, 11:6, 16:3, 4, 6), of the wicked (14:20). In all cases death is involved. The same is true in the rest of the NT where blood is used a metaphor for death (eg, Matt 23:30), unless it occurs in the phrase “flesh and blood” which is a metaphor for humanity as opposed to spirit beings (eg, Matt 16:17, 1 Cor 15:50 but never in Revelation).