Formation of the Earth, illustration. Image 3 of 12. Protoplanetary Earth forming in the early Solar System. The Earth formed from small rocky bodies (planetesimals) that accreted (due to gravitational attraction) in the protoplanetary disc of the early Solar System. As the planetesimals impacted the protoplanet, they turned the surface molten and triggered volcanic eruptions. The Earth formed around 4.6 billion years ago. Over time, it formed a molten interior and a magnetic field and collided with another body to form the Moon. Water accumulated to form oceans, the crust formed and plate tectonics began. As the Earth cooled, life emerged and evolved. For the full sequence, from the formation of the Earth to the emergence of life, see images C048/0082 to C048/0093.