Does anyone know what the mythological meaning of this apocalypse? i am interested to know...
It's hard to say if there is a special meaning to this apocalypse.
The two main sources of knowledge when it comes to Ragnarok are the Poetic Edda, which is a collection of poems collected by an unknown compiler, and the Prose Edda, which is usually attested to Snorri Sturluson. Ragnarok is also alluded to in a few sagas and þættir, but in those instances it's quite difficult to understand exactly what is meant, since old norse poetry relies heavily on so-called kennings - a type of mythological metaphores you can only understand if you know the myth or legend they're based on. Unfortunately, a lot of these have been lost.
In the Poetic Edda, the poem Völuspá gives a full account of the mythology concerning both the creation of the world and the apocalypse. According to the Völuspá, a number of events gradually make the gods weaker. At some point, three roosters will crow (Fjalar, a red rooster sitting in a tree - its name means "hider" or "deceiver", Gullinkambi (Goldencomb) in Valhöll, which is the golden rooster that wakes up the Einherjar every morning, and a nameless black rooster in Helheim). After this, the wolf Garmr, which had been chained up in the Gnipa cave, breaks free. Then the gods lose control and the world descends into chaos.
According to the Völuspá, "brothers will deliver bane-wounds onto each other, the children of sisters will break their kinship, there will be aggression in the world, a time of swords, lawlessness, and cleaved shields; a time of wind, and a time of wolves, before the world falls - no man will spare another."
Then the sons of Mimir, of whom we don't really know anything (presumably their role would have been much clearer if more material had been preserved), will do something and the god Heimdallr - a god with great hearing who keeps watch over Bifrost to ensure that no giants will enter Asgard, the realm of the gods - will blow his horn Gjallar. Odinn will ask the head of Mimir for advice, and the world-tree will shake as the entrance to Helheim is consumed by flames. Then all the evil creatures and the antagonists will begin to emerge: the giant Hrym approaches from the east with his magical shield, Jörmungandr - a giant seasnake which is large enough to wrap around the earth and bite its own tail - will make the oceans go all crazy, the giant eagle Hræsvælg ("corpse-eater") will scream, and the ship Naglfar (which is made from dead men's nails) will set sail and approach from the west, manned by the fire giants of Muspelheim and with Loki by the helm.
The gods will hold their final council, and the giant Surtr will approach from the south with his fiery sword and cause the heavens and earth to crumble. Then the final battle will be held. Odinn will die in battle against the wolf Fenris. His son Vidar will then kill the wolf. Freyr and Surtr will fight each other and both will die. Jörmungandr will rise up and descend from the sky to meet Thor in battle. Thor kills the snake, but he will only take nine steps before he falls over dead. Then, as the great protector of the world is dead, the earth will sink into the ocean, the sun and the stars will disappear, and the world will burn.
After a while, the world will rise again and the surviving gods will once again hold council. In some versions of the poem, there is an added verse in the end which speaks of an "almighty god" who will descend from above, but that's obviously a Christian addition. The story Gylfaginning in the Prose Edda adds some more details to what will happen after Ragnarok. For example, the sun has had a daughter before being swallowed by the wolf etc.
I've always liked the fact that everything is supposed to be cyclic, and that the world will emerge again after the apocalypse.