Tafsir of At-Takweer 81:3

That is, they are removed from their places on the earth due to the tremors that occur, with the "moving" (tasyir) being a metaphor for this. It has been said that they are moved after being lifted into the atmosphere, as the Exalted says: "And you will see the mountains, thinking them solid, while they pass like the passing of clouds." This will only occur after the second blowing of the Trumpet.