Revelation 6:12

There was a great earthquake

(σεισμος μεγας εγενετο). "There came a great earthquake." Jesus spoke of earthquakes in his great eschatological discourse (Mark 13:8). In Matthew 24:29 the powers of the heavens will be shaken. Σεισμος is from σειω, to shake, and occurs also in Revelation 8:5; Revelation 11:13; Revelation 11:19; Revelation 16:18. The reference is not a local earthquake like those so common in Asia Minor.As sackcloth of hair

(ως σακκος τριχινος). Σακκος (Attic σακος), Latin saccus, English sack, originally a bag for holding things (Genesis 42:25; Genesis 42:35), then coarse garment of hair (τριχινος, old word from θριξ, here only in N.T.) clinging to one like a sack, of mourners, suppliants, prophets leading austere lives (Matthew 3:4; Matthew 11:21; Luke 10:13). Here the hair is that of the black goat (Isaiah 50:3). Cf. Joel 2:10; Ezekiel 32:7; Isaiah 13:10; Mark 13:24. See Ecclesiastes 12:2 for eclipses treated as symbols of old age. Apocalyptic pictures all have celestial phenomena following earthquakes.As blood

(ως αιμα). In Acts 2:20 we find Peter interpreting the apocalyptic eschatological language of Joel 2:31 about the sun being turned into darkness and the moon into blood as pointing to the events of the day of Pentecost as also "the great day of the Lord." Peter's interpretation of Joel should make us cautious about too literal an exegesis of these grand symbols.