Chapter 1 - Of the Beginning of Days - J.R.R. Tolkien

The Silmarillion
The History of the Silmarils - Of the Beginning of Days
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The initial shape of Arda, chosen by the Valar, was of a symmetrical continent lit by two lamps wrought by Aulë the Smith, filled with light by Varda, and hallowed by Manwë: Illuin in the north, and Ormal in the south. Seeds of growth were planted by Yavanna which grew to fruition over Arda as greenery, grasses, and trees. The lamps illuminated all of the Earth, with both lights mixing in the center at the dwelling of the Valar: the isle Almaren in the middle of the Great Lake.

But as the Valar rested from their toils, Melkor delved, in secret, the fortress of Utumno beneath the mountains in the north. He came forth suddenly, taking the Valar at unawares, and destroyed the lamps. Thus the symmetry of Arda was marred, and Almaren was laid to ruin. Melkor fled to Utumno before the wrath of Manwë and Tulkas, and the Earth groaned in their wake. The might of the Valar was then put towards saving their labor, and they feared to put forth their power like so again, for they knew not where or when the Children of Ilúvatar would awake.

The Spring of Arda ended; the world was darkened and split into two main continents: Aman in the far West, and Middle-earth to the East, separated by the Great Sea. It was in Aman where the Valar made their new abode, and they raised up the Pelóri mountains as a fortification against Melkor, across the Sea of Belegaer, in Middle-earth. Manwë, chief of the Valar, set his throne upon the highest peak of the Pelóri: Taniquetil. Thus the Valar made for themselves a home in the utmost West, in Aman, which is called Valinor, and established the city of Valmar.

Melkor hid from the Valar in Utumno, which, after the marring, was in the north of Middle-earth. He surrounded himself with beasts of terror, many of them Maiar in the form of Balrogs. These were to remain some of his most faithful, and dreadful, servants.

At this time, all was dark. So, upon the mound of Ezellohar in Valinor, Yavanna, with the aid of Nienna, brought forth the Two Trees: the elder Telperion, with fluttering leaves of shining silver, and the younger Laurelin, from which shone forth a radiant, golden light. Thus began the Days of Bliss of Valinor, and the Count of Time.

Timeline of Arda:

Years of the Lamps
1900: Creation of the Two Lamps, Illuin and Ormal.
* Ordering of Arda by the Valar
* The Spring of Arda begins and the first plants and forests grow, and animals are awakened.
* Melkor's spies and secret friends, chief among them a great craftsman of the folk of Aulë, later named Sauron, inform him that the Valar are weary from their labors.
3400: Melkor returns in secret and builds Utumno and Angband.
* Melkor blights and poisons the bliss of the new world.
* The Valar become aware of Melkor's return and begin seeking his stronghold.
3450: Destruction of the Two Lamps and the isle of Almaren by Melkor and his followers.
* Spring of Arda ends
* Melkor retreats to Utumno while the Valar save what they can from the cataclysm.
* The Valar establish a new home in Aman and raise the Pelóri to defend it.
3500: Yavanna makes the Trees of the Valar.