A growing number of scholars have noted that in the Gospels, especially Matthew and Mark, the cross is described as a kind of apocalyptic event. We see this in the way the events of the passion narrative appear to parallel motifs in the apocalyptic discourse (Matt 24//Mark 13).
In the apocalyptic discourse tells the disciples to "watch" (13:5, 23, 33, 35, 37) because no one knows the when the "hour" of the judgment will come (13:32). He warns them not to let the master find them sleeping (13:36). He warns that the disciples will be betrayed by their family members (13:12-13) and handed over to Jewish and Roman authorities (13:9-13). He warns that the temple will be destroyed (Mark 13:2). He speaks of things such as “darkness” covering the land (Mark 13:24; Mark 15:33) and earthquakes (Mark 13:8).
When you read the Passion narrative--the account of Jesus’ suffering and death in the Gospels--alongside this apocalyptic sermon it is clear that Jesus’ own death is being described as a sort of apocalyptic event.
Jesus goes out to a garden to pray, telling the disciples to "watch" with him (cf. (Mark 14:34, 37-38)--though he finds them sleeping. He explains that in fact his “hour” is at hand (13:41).
Judas comes and arrests him—as Jesus warns the disciples they would be betrayed by family and handed over to authorities, Jesus is betrayed by one of the twelve (14:10, 20, 43) and handed over to Jewish and Roman authorities (14:10-11, 18, 21,41-42; 15:1, 10, 15).
Once he is crucified, darkness covers the land (Mark 15:33), there is an earthquake (Matthew 27:51), and the veil in the temple is torn, symbolizing its destruction (15:38). Matthew even tells us that some of the dead were raised (Matthew 27:52).
The cross then is then truly described as a kind of cosmic / apocalyptic event.
 See, e.g., R. H. Lightfoot, The Gospel Message of St. Mark (Oxford: Clarendon Press, 1950), 48-59; Dale C. Allison, The End of the Ages Has Come: Early Interpretation of the Passion and Resurrection of Jesus (London: T & T Clark, 1987), 36-38; John T. Carrol and Joel B. Green, The Death of Jesus in Early Christianity (Peabody, MA: Hendrickson 1995), 36-7.