Over time, Earth's interior—which is made mostly of silicate rocks and metals—differentiated into four layers. At the planet's heart lies the inner core, a solid sphere of iron and nickel that ...

Seafloor is made of a denser rock called basalt, which presses deeper into the mantle, producing basins that can fill with water. Except in the crust, the interior of the Earth cannot be studied ...

Prehistoric time line, geologic time scale, photos, facts, maps, and more from National Geographic. Humans have walked the Earth for 190,000 years, a mere blip in Earth's 4.5-billion-year history.

See phenomenal photos of the world's wonders from the September 2016 issue of National Geographic magazine ... This image was made by digitally stitching together more than 300 30-second exposures ...

Exclusive photos reveal a sprawling, 300-year-old coral near Solomon Islands, recently discovered by the National Geographic ...

Scientists said on Thursday they found what is believed to be the world's largest coral, which has been growing undisturbed ...

This story appears in the August 2017 issue of National Geographic magazine ... which rain down constantly on Earth, in Antarctica and other pristine locations, but Larsen thought there should ...