What does Revelation 16:20 mean?

The earthquake not only destroys cities but also triggers massive geological change. Earthquakes are a major cause of tsunamis, and this earthquake is so massive that islands are noticeably moved. The earthquake also flattens mountains. The world will undergo tremendous topographical changes that include changes to Israel's landscape. The Mount of Olives will split into two. One half of the mountain will move northward; the other half will move southward (Zechariah 14:4). This event will create a very wide valley. After the tribulation, Jerusalem will become a seaport (Zechariah 14:8). The mountainous parts of Israel will disappear (Revelation 16:20). A river will begin its flow from Jerusalem and enter the Dead Sea, making this otherwise unproductive body of water a productive place for fishermen (Ezekiel 47:7–10).

Also, the barren desert will become fertile. Isaiah 35:1 prophesies: "The wilderness and the dry land shall be glad; the desert shall rejoice and blossom like the crocus." Verse 6 says waters will gush forth in the wilderness, and streams in the desert. Verse 7 predicts that the burning sand will become a pool and thirsty ground will become springs of water.