﴿ وَجَعَلْنَا فِى ٱلْأَرْضِ رَوَٰسِىَ أَن تَمِيدَ بِهِمْ وَجَعَلْنَا فِيهَا فِجَاجًۭا سُبُلًۭا لَّعَلَّهُمْ يَهْتَدُونَ ﴾

“And [are they not aware that] We have set up firm mountains on earth, lest it sway with them, and [that] We have appointed thereon broad paths, so that they might find their way,”

وَجَعَلْنَا فِي الْأَرْ‌ضِ رَ‌وَاسِيَ أَن تَمِيدَ بِهِمْ (And We created mountains on the earth, lest it should shake with them. 21:31) The word مَید (mayd) in Arabic language means to be convulsed. Therefore, the meaning of this verse is that Allah Ta` ala has planted mountains on the earth to hold it in place because any violent movement of the earth would be catastrophic to those who live on it.