 |
 |
 |
 |
 |
|
DEEP TIME国外网站网页设计欣赏 
DEEP TIME国外网站网页设计欣赏 
The Hadean Eon9 is named after the god Hades, which is Greek for Underworld, and generally refers to the chaotic conditions on the early Earth. At the start of the Hadean the solar system was still forming within it's accretion disc9.1 and the planet was subjected to millions of years of violent impacts known as the Late Heavy Bombardment9.2. This was a time on Earth before there were any rocks, making geological study of this eon very difficult. The oldest dated material from this time were crystals formed from zircon. Around 3.8 billion years ago the Earth entered the Archaen Eon10. During this time the Earth's crust cooled and rocks and continental plates began to form. 300 million years-in the Earth's magnetic field was established, protecting the early planet from intense solar winds capable of stripping away any atmosphere which existed. Fossils of stromatolites, which were instrumental in creating the free oxygen in the atmosphere are found throughout the Archean, becoming especially common late in the eon. The Proterozoic Eon11 is the largest classified time period extending 2 billion years. The name Proterozoic is Greek for earlier life. We have a much better geologic record of this time as many of the rocks are less metamorphosed than from the Archaen Eon. The first-known glaciations occurred during the Proterozoic, one began shortly after the beginning of the eon, while there were at least four during the Neoproterozoic, climaxing with the Snowball Earth of the Varangian glaciation. The current Eon in the geologic timescale is the Phanerozoic covering roughly the last 545 million years. Here, this infographic splits into 3 Eras, the first of which is the Paleozoic Era12. During this time the Earth's landmass was broken up into a substantial number of relatively small continents. Towards the end of the era, around 251 million years ago, sophisticated reptiles and the first modern plants had developed. The continents gathered together into a supercontinent called Pangaea, which included most of the Earth's land area. The Mesozoic Era13 is the second period during the Phanerozoic Eon and extended from 251–65 million years ago. This was the Age of Dinosuars6 but also a time of intense tectonic, climatic, and evolutionary activity. The gradual drift of the continents towards their present positions resulted in the end of the supercontinent Pangaea. The climate was exceptionally warm throughout the period; this also played an important role in the evolution and diversification of new animal species. By the end of the era, the basis of modern life was in place. The Cenozoic Era14 is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 million years ago to the present. It is marked by the Cretaceous–Tertiary extinction event14.1 at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and the end of the Mesozoic Era. The Cenozoic Era is ongoing. http://deeptime.info/ 
|
