The Thunder - 13:3
He built the earth and placed on it firm mountains and rivers and every kind of fruit He created, male and female. He covers the night with the day. Surely in this are signs and lessons for a thinking people.
Why were firm mountains placed on the earth?
The Bee/16:15
And He has placed in the earth stabilizers so that you may not be shaken, and rivers and roads so that you may find the way,
Luqman/31:10
He created the heavens without a pillar that you see. And He placed stabilizers on the earth that you may not be shaken, and He spread therein every kind of creature. And We rained down water from the sky, and We caused to grow therein every beautiful variety.
The Prophets/21:31
We placed mountains on the earth so that it might not shake them, and We made in it wide passages for them to find the way.
Those Who Pull Out/79:32
He has also made the mountains.