Is there any canon lore anywhere about these periods? (1rst, 2nd, 3rd and 5th worlds)
Wanted to make a Shadowrun game with past "proofs" of earthdawn... and it hit me right in the face... what's BEFORE earthdawn?
The link between Earthdawn & ShadowRun dates from when FASA had firm control of both licenses. Once that line was cut, everything about this was dropped.
Background: the magic in the world has a cyclic nature with bad things happening at certain points in that cycle. Those bad things are called Horrors and every now and then (when the world is filled with magic) they breach from another plane and feast on the environment (rocks, plants, animals, human emotions). This in general is considered a bad thing (they take their time to eat everything) and generally plummets the planet back to stone age level of technology.
The First Age: nobody is really sure what happened here. If you want to know more, go talk with a Great Dragon.
Age of Dragons: the dragon's had firm control and created servants (Immortal Elves). As with all servants, rebellion followed. The Horrors popped in and laid waste to the world. The Books of Harrow are rumoured to date from this age.
The 3rd age is vague at best. You could use this as an alternate description of what is happening. Doing so would move the Dragon servant to this age.
Age of Legend is the default setting of Earthdawn. It ends with the horrors stopping by. The Therian empire is the source for all Atlantis myths.
The 5th age is current time.
The 6th age is ShadowRun and it's speeding towards Horror arrival. The Great Ghost dance was used to hasten the arrival of the horrors. The arrival of the insect spirits was another sign, that everything was going faster then normal (Lofwyr was surprised that they arrived so soon, he wasn"t expecting them for another 200 years). Dunkelzahn killed himself to slow that speedup down.
If you would like to know more and are willing to read some books: