Assalamu alaikum wa rehmatullahi wa barakatuh
And He has set up on the earth mountains standing firm, lest IT [the earth] should shake with you; and rivers and roads; that ye may guide yourselves; 16:15
Is not He (better than your gods) Who has made the earth as a place of settlement, and has placed rivers in its midst, and has placed firm mountains therein, and has set a barrier between the two seas (of salt and sweet water). Is there any ilah (god) with Allah? Nay, but most of them know not. 27:61
He created the heavens without any pillars that you can see; He set on the earth mountains standing firm, lest it should shake with you; and He scattered through it beasts of all kinds. We send down rain from the sky, and produce on the earth every kind of noble creature, in pairs 31:10
Have WE not made the earth as a bed, And the mountains as pegs? 78:6-7
Isostasy and Mountains:
According to Encyclopedia Britannica,
isostasy, ideal theoretical balance of all large portions of Earth’s lithosphere as though they were floating on the denser underlying layer, the asthenosphere, a section of the upper mantle composed of weak, plastic rock that is about 110 km (70 miles) below the surface. Isostasy controls the regional elevations of continents and ocean floors in accordance with the densities of their underlying rocks.
According to Wikipedia,
Isostasy (Greek ísos “equal”, stásis “standstill”) is the state of gravitational equilibrium between Earth’s crust and mantle such that the crust “floats” at an elevation that depends on its thickness and density.
When continents collide, the continental crust may thicken at their edges in the collision. If this happens, much of the thickened crust may move downwards rather than up as with the iceberg analogy. The idea of continental collisions building mountains “up” is therefore rather a simplification. Instead, the crust thickens and the upper part of the thickened crust may become a mountain range.
Polar Motion and isostasy:
The Earth’s rotation axis moves with respect to the fixed stars (inertial space); the components of this motion are precession and nutation. The Earth’s crust also moves with respect to the Earth’s rotation axis; this is called polar motion.
The slow drift, about 20 m since 1900, is partly due to motions in the Earth’s core and mantle, and partly to the redistribution of water mass as the Greenland ice sheet melts, and to isostatic rebound, i.e. the slow rise of land that was formerly burdened with ice sheets or glaciers.