﴿ يَوْمَ تَرْجُفُ ٱلْأَرْضُ وَٱلْجِبَالُ وَكَانَتِ ٱلْجِبَالُ كَثِيبًۭا مَّهِيلًا ﴾

“on the Day when the earth and the mountains will be convulsed and the mountains will [crumble and] become like a sand-dune on the move!”

Please check ayah 73:18 for complete tafsir.