The age of the earth is estimated at 4.6 billion years. During the course of this immense period of time, the earth evolved from a cloud of cosmic dust, undergoing constant changes into what we know today.
The earliest era, called Precambrian, encompasses the time period from the very first beginnings of the earth to the time when the first rocks appeared. These rocks contained petrified residues from which it was possible to determine the age of one layer of rocks. No petrified remnants dating back to the Precambrian proper were found. It is not possible to provide any precise information concerning the formation of the rocks of that time because, since that time, the earth has been undergoing constant changes. It is possible to classify only certain processes of the origins of the mountains (most importantly in Northern America, Scotland, and Greenland - Laurentian Plateau formation).
