Luke 21:11 says, "And great earthquakes shall be in divers places, and famines, and pestilences; and fearful sights and great signs shall there be from heaven." This definitely constitutes as a fearful sight. Mark 13:8 says, "For nation shall rise against nation, and kingdom against kingdom: and there shall be earthquakes in divers places, and there shall be famines and troubles: these [are] the beginnings of sorrows." This definitely constitutes a trouble. It is these noticeable events that Jesus spoke of.