In a rock, it is found that there is three times as much daughter element as parent element. The parent element has a half-life of 1 billion years. The oldest rock on Earth is 4.6 billion years old. The asthenosphere is composed of a different type of rock than the mantle. The Earth's inner core is liquid.
Ocean crust is denser than continental crust.
Planets were drawn together by the process of differentiation. Earth's temperature is warmest at the surface and coldest on the interior. The solar system formed from a rotating cloud of gas.