The Earth as a Geode
The easiest way to visualize the formation of the hollow earth is to look at the best example that we have in nature ... that of a geode. Geodes range in size from small rock formations all the way up to large caverns filled with crystals. These features typically form when rock is found in its igneous state and then hardens around a gas bubble.
To bring this around to hollow earth, imagine a large spinning bubble of molten material that slowly cools and hardens into a dense, crystalline shell. This is hollow earth. Now imagine, if you will, the brilliance that can be seen from the inside of the earth. If geodes are to be any indicator, there is considerably more going on inside this planet than there is on the surface. In fact, I'd go as far to say that most planetary bodies were never intended for life on their surface. The inside, on the other hand ... that remains to be seen!
The important thing to remember is that the shell of the earth is basically one large crystalline form. Imagine a crystal the size of the earth ... or more accurately a geode!