IT took the earth this long to cool enough to form rocks
The answer is debated amongst geologists, astrologists and palaeontologists - the earliest period in life's history is the Archean eon, when the first proto-cells were thought to have formed. The earliest period there, is the Eoarchean - 4200 - 4400 million years ago. However, the earliest eon is the Hadean, which encompasses the formation of the Earth as celestial body 4600 million years ago, up to 4200 million years ago. The earth was formed by accretion (gravitational attraction of smaller bodies, to form a central object of greater mass, thus attracting more smaller bodies, and so on), within 10 - 20 million years, so, other than describing this period of Earth's history as 'Proto-Earth', there isn't really a way of classifying even earlier stages, unless you are willing to look into the stages of accretion in forming planets. (The earliest stage would probably be a 'proto-planetary disk' stage, which was itself formed as a by-product of the formation of the sun, followed by a kilometre-wide planetisimal, and then a Mars sized 'embryo', growing progressively. In this sense, the Earth and the Sun are descended from the same Giant Molecular Cloud, or GMC.)
About 500 million years after Earth formed
ScienceDaily (Sep. 7, 2011) - Ultra high precision analyses of some of the oldest rock samples on Earth by researchers at the University of Bristol provides clear evidence that the planet's accessible reserves of precious metals are the result of a bombardment of meteorites more than 200 million years after Earth was formed.
The Earth was formed 4.567 billion years ago from material accreted around the newly formed Sun.
Samples of Earth's crust contain less iron than found in meteorites, and iron is a comparatively heavy element that would have sunk into the planet when it was being formed.
earth cooled suffciently
Nobody really knows when the earliest organisms were on Earth. It was definitely more than a million years ago.
Because it was not man-made. The moon was formed a few million years after the earth and almsot 4 billion years before our earliest ancestors.
Because it was not man-made. The moon was formed a few million years after the earth and almsot 4 billion years before our earliest ancestors.
The answer is debated amongst geologists, astrologists and palaeontologists - the earliest period in life's history is the Archean eon, when the first proto-cells were thought to have formed. The earliest period there, is the Eoarchean - 4200 - 4400 million years ago. However, the earliest eon is the Hadean, which encompasses the formation of the Earth as celestial body 4600 million years ago, up to 4200 million years ago. The earth was formed by accretion (gravitational attraction of smaller bodies, to form a central object of greater mass, thus attracting more smaller bodies, and so on), within 10 - 20 million years, so, other than describing this period of Earth's history as 'Proto-Earth', there isn't really a way of classifying even earlier stages, unless you are willing to look into the stages of accretion in forming planets. (The earliest stage would probably be a 'proto-planetary disk' stage, which was itself formed as a by-product of the formation of the sun, followed by a kilometre-wide planetisimal, and then a Mars sized 'embryo', growing progressively. In this sense, the Earth and the Sun are descended from the same Giant Molecular Cloud, or GMC.)
About 500 million years after Earth formed
The origins of most mineral samples were terrestrial. This means that they were naturally formed on Earth, and were not extra-terrestrial.
Earth cooled sufficiently
The answer is debated amongst geologists, astrologists and palaeontologists - the earliest period in life's history is the Archean eon, when the first proto-cells were thought to have formed. The earliest period there, is the Eoarchean - 4200 - 4400 million years ago. However, the earliest eon is the Hadean, which encompasses the formation of the Earth as celestial body 4600 million years ago, up to 4200 million years ago. The earth was formed by accretion (gravitational attraction of smaller bodies, to form a central object of greater mass, thus attracting more smaller bodies, and so on), within 10 - 20 million years, so, other than describing this period of Earth's history as 'Proto-Earth', there isn't really a way of classifying even earlier stages, unless you are willing to look into the stages of accretion in forming planets. (The earliest stage would probably be a 'proto-planetary disk' stage, which was itself formed as a by-product of the formation of the sun, followed by a kilometre-wide planetisimal, and then a Mars sized 'embryo', growing progressively. In this sense, the Earth and the Sun are descended from the same Giant Molecular Cloud, or GMC.)
Rock Samples.
ScienceDaily (Sep. 7, 2011) - Ultra high precision analyses of some of the oldest rock samples on Earth by researchers at the University of Bristol provides clear evidence that the planet's accessible reserves of precious metals are the result of a bombardment of meteorites more than 200 million years after Earth was formed.
It was formed by by the movement of earth's crust about 40 million years ago.