The destruction of the Mountains, and the Earth becomes a Smooth Plain

Allah says,

وَيَسْـَلُونَكَ عَنِ الْجِبَالِ

يُنفَخُ فِي الصُّورِ‌ (رضی The Day when the Horn الصُّورِ‌ [ Sur ] will be blown - 20:102) According to Sayyidna Ibn ` Umar اللہ تعالیٰ عنہما ، a Bedouin الصُّورِ‌ asked the Holy Prophet ﷺ about صُور (the Horn) to which he replied that it is something like a horn which will be blown, meaning thereby that when the angel will blow into it all those who had lain dead for centuries will return to life. Only Allah knows the true nature of the Sur (the Horn).