There are some factors leading to the earth expansion, while other factors lead to its contraction.
The earth contraction:
Obviously, when it becomes colder and colder, it will contract .. leading to breaking of its surface; therefore, large fissures and rifts may then occur and may also lead to some mountainous ranges appearing: some parts of the earth surface will depress and other parts will elevate.
This is the cooling of the earth in general particularly its core as it cools by heat radiation and the eruption of volcanoes... it is not the Global Warmth which almost affects the earth surface, not the earth core.
Here is about the earth contraction:
The expansion of the earth, on the other hand, is due to the falling down on it of a large number of meteoritic rocks and large amounts of cosmic or celestial dust, which is a continuous process.
And this is about its expansion (specially in the past)
">> (and He made [mountains] that landed upon it); that which heavily landed upon the earth, are the mountains. This can be explained as follows:
That sun had been transformed into an earth after the cooling of its surface, then the meteorites started to fall down on it to become the mountains. Therefore, most of the mountains on the earth surface were originally meteorites.
>> (and blessed it) means: He increased its size, and that was by many factors :
First: The crust of the earth started gradually to be colder more and more; so this increased its thickness.
Second: The falling down of meteorites upon it increased its mass and volume.
Third: The falling down of minute particles upon it (these are the fine particles that we see in a beam of sun rays entering a dark room through a window.) The origin of these particles is from the meteorites which were broken up after their Doomsday, so that their parts scattered in the space.
Fourth: The metals increased its volume and size by combination with other elements, e.g. the oxygen may combine with iron, so it will increase its volume, and ferric oxide will result; and carbon dioxide combines with calcium forming calcium carbonate; and nitrogen combines with sodium and potassium resulting in sodium nitrate and potassium nitrate; and so on gases combine with most of the metals to increase their volume, and by this way the Earth size goes on increasing with the passing of time and years."