Iron sinks deep inside Earth and forms its core. Lighter elements like silica, magnesium, and aluminum rise to the surface, and later harden to form the outer crust. 4,200 mya: Great oceans form ...

Chunks of Earth's primordial crust, or original crust ... The mantle is hot, dense, iron and magnesium-rich solid rock which is up to 2,900km thick. The core is the planet's centre and is made ...

Earth bubbles and broils beneath an underwater peak called Axial Seamount, located 480 kilometers (300 miles) off Oregon's ...