Revelation 8:8-9 The second angel sounded his trumpet, and something like a huge mountain, all ablaze, was thrown into the sea. A third of the sea turned into blood, a third of the living creatures in the sea died, and a third of the ships were destroyed.
When the first trumpet sounded, hail mixed with fire burned one third of the land. Now the second trumpet damages one third of the seas. A huge blazing mountain is thrown into the sea and one third of all sea life and shipping are destroyed.
“Something like a huge mountain” in the sea is reminiscent of a volcanic event in the Mediterranean world. The eruption of Mount Vesuvius was a recent event for the first readers of Revelation, even although Ephesus was more that 1000 miles from Pompeii the eruption of Vesuvius was a well-known event. Some Jews believed Vesuvius was a judgment of God on the Romans for destroying Jerusalem in AD 70. Pliny reported that some sea creatures were stranded on dry land. Volcanic debris blocked the Bay of Naples and sea levels dropped.
Pliny Epistles, 6.20 Then we beheld the sea sucked back, and as it were repulsed by the convulsive motion of the earth; it is certain at least the shore was considerably enlarged, and now held many sea animals captive on the dry sand. On the other side, a black and dreadful cloud bursting out in gusts of igneous serpentine vapour now and again yawned open to reveal long fantastic flames, resembling flashes of lightning but much larger. (Trans. William Melmoth, LCL, 1:493.
Some read the “great mountain” as a meteorite striking the earth. Certainly this would cause a great deal of destruction to the sea, but volcanic activity is far more common in the Mediterranean world than meteor strikes. It is important not to read this sea as the Atlantic or Pacific oceans, but rather the Mediterranean Sea. The Roman Empire relied on the Mediterranean for fishing and commerce, so whatever the “burning mountain” is, it destroys one-third of the shipping on the Mediterranean and destroys one-third of the food supply.
However, in the Old Testament, nations are sometimes described as mountains. In Jeremiah 51:25 for example, Babylon is a great destroying mountain. When the Lord stretches his hand against Babylon, it will become a “burnt mountain.” Greg Beale concludes the second trumpet is “the judgment of a wicked kingdom” (Revelation, 476).
The sea “turning to blood” recalls the first of the ten plagues, the Nile turning to blood. Just as the Mediterranean. The Nile was necessary for life in Egypt. To attack the Nile was to threaten all life in Egypt. In a similar way, to destroy one third of the shipping in the Mediterranean would cripple the economy and military strength of the Empire. Looking ahead to Revelation 18, God’s judgment falls on the economy of Babylon, although the imagery clearly has the Roman Empire in mind.
Destructive burning mountains appear in other apocalyptic as well. In the Sibylline Oracles:
Sib. Or. 4.130-34 But when a firebrand, turned away from a cleft in the earth in the land of Italy, reaches to broad heaven, it will burn many cities and destroy men. Much smoking ashes will fill the great sky, and showers will fall from heaven like red earth.
Sib. Or. 5.512–514, 528-31 I saw the threat of the burning sun among the stars and the terrible wrath of the moon among the lightning flashes. The stars travailed in battle; God bade them fight… 528-31 Heaven itself was roused until it shook the fighters. In anger it cast them headlong to earth. Accordingly, stricken into the baths of ocean, they quickly kindled the whole earth. But the sky remained starless.
In both these examples, it is likely a volcanic eruption is the source of the apocalyptic imagery. What is important here is the continued use of the plagues as a model for God’s judgment on the empires of this world, focusing here on devastating the economy of the empire.