And man will say;"What is the matter with it"
meaning, he will be baffled by its situation after it used to be stable, settled and firm, and he used to be settled upon its surface.
This refers to the alteration of the state of things and the earth moving and shaking. There will come to it inescapable quaking that Allah prepared for it. Then it will throw out its dead people -- from the first to the last generations. At that time the people will be baffled by the events and the earth changing into other than the earth, and the heavens as well. Then they will be presented before Allah, the One, the Irresistible.
Concerning Allah's statement,
يَوْمَيِذٍ تُحَدِّثُ أَخْبَارَهَا