(Ambiya') 21 : 31
وَجَعَلْنَا فِي الْأَرْضِ رَوَاسِيَ أَنْ تَمِيدَ بِهِمْ وَجَعَلْنَا فِيهَا فِجَاجًا سُبُلًا لَعَلَّهُمْ يَهْتَدُونَ
And We placed within the earth firmly set mountains, lest it should shift with them, and We made in it roads that they might be guided.
Adhikr is the Balance and Trust to keep the universe in its equilibrium as told in verse 33: 71-73. Hills and mountains are cast on earth as nails for keeping the earth in its equilibrium as explained in verse 16: 15-16. See explanation 16: 6 and 61.