Fearless Planet
Fearless Planet
Starting with the earth’s origins 4.5 billion years ago, the first eon in the Earth’s history is called the Archaean. It lasted until 2.5 Ga (billion years ago). The oldest rocks found on Earth date to about 4.0 Ga. The timespan between the age of those oldest rocks and the formation of the Earth is sometimes seen as a separate eon, called the Hadean. Because no material from this time is preserved, little is known about Hadean times. The Earth’s surface must have been under an intense bombardment of meteorites and volcanism must have been severe due to the large heat flow and geothermal gradient. Sometimes sporadic detrital zircon crystals are found older than 4.0 Ga, and they show evidence of having been in contact with liquid water 4.3 Ga. This is proof that the planet already had oceans or seas at that time. From crater counts on other celestial bodies it is known that the intense meteorite bombardment (Late Heavy Bombardment) came to an end about 3.8 Ga. At the beginning of the Archaean eon, the Earth had cooled considerably. Due to the composition of the atmosphere, life would have been impossible for most present life forms, because of the lack of oxygen and absence of an ozone layer.
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EPISODE ONE – Earth Story
EPISODE TWO – Grand Canyon
About the formation of the Grand Canyon.
