The known Dragon Breaks are:
1) The Marukhati Selective Dragon Break
2) The Warp in the West that results in dozens of kingdoms around the Iliac Bay becoming four while Talos and Mannimarco undergo apotheosis
3) The first activation of Numidium
4) The Tribunal tapping into the power of the Heart of Lorkhan which may or may not be related to the disappearance of the Dwemer
There are many interesting books on the topic such as Where Were You When the Dragon Broke?, The Dragon Break Re-Examined, and The Warp in the West.
This portion of issue 199 of Game Informer provides a little background (Taken from my post on Towers and Stones)
The Dragon Breaks are large gaps in time when nothing occurs, they may be related to Akatosh, God of Time. The Maruhkati Selective, a sect of the Alessian Order may have correlations with the first Dragon Break. When a Dragon Break occurs, everyone in Tamriel, possibly in the entire planet Nirn fall unconscious and can't remember anything that goes on during the break. Khajiit claim to be able to see through the events of the Dragon Breaks, suggesting some relation to Moon Sugar (used to make skooma). See here for more info on the Khajiit.Game Informer wrote:All the organization in the world can't hold back Murphy's Law, but sometimes companies find a playful way to deal with narrative discrepancies. "One of the main things we've always done with the Elder Scrolls is to maintain deniability" explains Kurt Kuhlman, a senior game designer at Bethesda Softworks. "As long as the lore is presented from the point of view of someone within the fictional world, it's okay for someone else from within the world to have a different point of view. As soon as we step outside the game and say 'This is actually true.' it's much harder to reconcile any contradictions."
A classic example of this in the Elder Scrolls lore is referred to as "The Dragon Break." During development of Morrowind, the writers at Bethesda noticed a gap in their timeline. Nothing happened historically over a period of over 1,000 years. Details of the world's history jumped from the year 1190 to the year 2260, when the later date likely should have been 1260. The gap was likely a result of a typo that happened when someone input dates on Bethesda's internal timeline. But before the typo was discovered, the game's fiction had already expanded past the point of making a simple fix. Events and details taking place after 2260 had already been established, so altering the world's chronology would have been a massive headache. The solution? Maintain deniability
"One of the designers decided to jump on that and started writing about the Dragon Break - an event where a group of religious fanatics actually 'broke time' through some esoteric ritual," Kuhlman explains. "I responded with another in-game book, The Dragon Break Reconsidered, which explained away the lost 1,200 years as a simple error in interpreting ancient records." Which of these explanations is true Elder Scrolls lore? Bethesda has never officially specified, and likely never will.
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