Amos 8:8

Because of the sins just described the land would quake from the Lord’s approach and the large enemy army that He would lead against Israel. Perhaps a literal earthquake did occur, but probably trembling with fear is in view (cf. 2 Samuel 7:10). All the inhabitants would mourn over the coming destruction. The waves of terror and destruction would be like the rising and falling of the Nile River.

"Since the rise and fall of the Nile usually extended over a few months, some national upheaval lasting a considerable period of time is implied by the analogy. Sometimes the flooding of the Nile was highly destructive. Amos may have been comparing the destructiveness of social injustice, civil strife, economic exploitation, and religious shallowness in Israel to the destruction caused by the inundation of the Nile. The flooding of the Nile occurred repeatedly, as did the social, civil, economic, and religious problems of society." [Note: B. Smith, p. 148.]