The Hadean Time And The Formation of The Earth

4.5 to 3.8 Billion Years Ago

The Hadean period is reprsented by the first hour and fifty minutes of the Clock. The nature of the Hadean has generally been believed to be a turbulent time of extreme heat and volatile gravitational collapse. In fact, it got its name from the images we generally hold of Hades, the mythological underground. However, there are scientists that as recently as May, 2005 are presenting new evidence that the earth may have already begun to cool during this time period and that life could have been possible. Stay tuned!

Scientists have generally thought that during the Hadean period the solar system was forming out of a spinning cloud of dust and gases called an accretion disk. At the center of the cloud, heavier particles drew together through gravitational force until nuclear fusion set it ablaze in light and heat. This, of course, was the birth of our sun.

Star forming nebula

Photo:NASA

But the solar particles were not the only particles present in the accretion disk. Other particles were lumping together to form microplanets (similar to modern asteroids), larger planetesimals, and the planets of our solar system.

Scientists also believe that the Earth and other planets would have been molten at this stage of development. As the Earth cooled, the heavier molten iron sank into the core, while lighter rock rose to the surface, cooled and became the crust. The oldest known Earth rocks to date are approximately 3.8 billion years old. Meteorites and lunar rocks have been found to be approximately 4.5 billion years old. With the formation of solid rock, Earth�s geological history began.

Galaxy

Photo: NASA

For more on geologic time go to the clock of eras page

or The Geologic Time Line