THE EARTH:

THE EARTH IS MADE UP OF THE INNER CORE, OUTER CORE, MANTLE, AND CRUST. THESE ARE LATER SUB-CATEGORIZED. THESE ARE THE FOUR PARTS OF THE EARTH.

THE CRUST:

The Earth's crust is the site of chemical exchange between the hydrosphere, atmosphere, and the Earth's interior.  Earth's mantle and crust formed about 100 million years after the formation of the planet, about 4.6 billion years ago. At first the crust was very thin, and was probably changed often as the tectonic plates shifted around a lot more than they do now.  The Oceanic Crust is about 3 mi to 6 mi thick and composed primarily of denser, more mafic rocks, such as basalt, diabase, and gabbro. Continental os about 20 mi to 30 mi thick and mostly composed of less dense, more felsic rocks, such as granite.