In the very ancient history of Middle-earth, before the Two Trees were made and before the first Elves had awoken, the Valar drove Melkor out of the world after long ages of conflict. At that time the Valar created the first light when they raised two great Lamps held high on immense pillars to illuminate the young world. One of these stood in the south, named Ormal, while its mate Illuin shone on the northern lands, and their light met and mingled in the central regions of Middle-earth. Based on the names of these Lamps, it seems that Ormal shed a golden light (while the light of Illuin was blue).
These two Lamps of the Valar stood for millennia, and in their light the first growing things began to sprout in the time known as the Spring of Arda. In this time the Valar rested on the green isle of Almaren, but in the darkness of the far North Melkor was busy. He had returned to the world in secret and begun the building of the great fortress of Utumno, unknown to the Powers on their isle far to the south.
Suddenly Melkor emerged from his hidden fortress and assaulted the Lamps. Ormal and Illuin both fell, their pillars broken and their inner fires spilling out across the earth. The lands were shattered in their fall, and new seas created where they had once stood.3 Shocked by this unforeseen assault, the Valar abandoned Middle-earth and travelled to a distant new land in the far West beyond the Great Sea. To give light to that land, they made the Two Trees of Valinor, but with the loss of the Lamps, Middle-earth was left in darkness for many thousands of years.
Notes
1
The dating values shown here are taken from The Annals of Aman in volume X of The History of Middle-earth, but note that there is some uncertainty over the precise values. For a detailed discussion, see Note 1 to the entry for the Lamps of the Valar.
2
The name Ormal is not explained, but it seems to combine the Elvish prefix or- (indicating a high, rising or prominent thing) with mal 'gold'. Or can also mean 'day', but this connection seems very unlikely to apply to Ormal. The etymological roots of or as 'day' lie in the rising of the Sun, which did not exist in the time that the light of Ormal shone on the world.
3
The fall of the northern lamp Illuin created a wide inland sea, the Sea of Helcar. Based on early sketch maps (in volume IV of The History of Middle-earth), there was similar sea in the south, which implies that the fall of Ormal created an inland sea of its own. On that map, the southern sea is labelled as the 'Sea of Ringil', and Ringil was an earlier name for Ormal, which seems to confirm that Ormal's fall was responsible for its creation.