Second Fracture

The Second Fracture is the third recorded case of world-class magic being used and caused the second phase of splitting the planet up into the Ipholic Plates we see on Ipholas today. The Second Fracture uplifted Ipholas' crusts from the mantle of the earth and tore them apart along their techtonic boundaries, separating them with massive ravines leading straight into the Underdark and below.
The Second Fracture was caused by a coordinated casting of world-class seismic magic by grand scalemages of the Nagakin empire which ended the Scale Wars. Similar to the events of the First Fracture, the casting was performed by four groups of Nagakin mages approximately twenty-large and lead by two-to-three grand scalemages that positioned themselves at "the four corners of the world," areas of high seismic activity.
Following the third casting of world-class magic, the goddess of Magic, Mystra, punished the arrogance of the mortals of Ipholas by shattering the weave and inducing Ipholas' Spellplague. Although traditional arcane magic was impossible to perform during this time, new forms of magic were developed in its wake, including void magic, veriturgy, and cruoromancy.