<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> The geological history of Earth follows the major events in Earth's past based on the geologic time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk - shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System . </P> <P> Earth was initially molten due to extreme volcanism and frequent collisions with other bodies . Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere . The Moon formed soon afterwards, possibly as a result of the impact of a planetoid with the Earth . Outgassing and volcanic activity produced the primordial atmosphere . Condensing water vapor, augmented by ice delivered from comets, produced the oceans . </P>

When does the geological record indicate that the earth formed