The Pre-Cataclysm world event phase 1 introduced the new Horde quests and Alliance quests to uncover the Twilight’s Hammer infiltration in Orgrimmar and Stormwind, but also the beginning of elemental invasions to several locations across Azeroth.
The video shows two elemental invasions in Zul’Drak and Sholazar Basin. The best way to identify a spawning location is looking for a fight between NPC mobs and elementals. These invasions usually happen in areas where there are shamans or elementalists.
You can’t attack the rifts directly. In order to destroy them you have to kill a certain amount of elementals to cause damage to the rift. At the end you will see a device which triggers a daily quest titled: Hammering it Out.
There are four types of invasions by zones: Air, Water, Earth or Fire. You can find the locations and coordinates here.
Destroying a rift from each elemental type will grant you a Feat of Strength Achievement titled: Tripping the Rifts.