Rifts are small disturbances in reality.
Destroying rifts inside cataclysms can provide temporary stability to anything and fill the stability meter of a Javelin. However, the rifts can form back again.
Rifts can only be found hovering above an arena or above the spear in the Echoes Heart chamber.
Pockets of Stable Reality[]
Just like rifts, there are Pockets of Stable Reality which are smaller but permanent safe zones. They completely fill the stability meter of the javelin.
Inside one of these pockets, the storm seems to completely disappear, and reveals how the cataclysm would be without it.
The map below shows the regions containing Rifts and Pockets of Stable Reality.