Thursday, January 31, 2013

Pre-Cambrian


The pre-Cambrian is the name given to all of geological time before the Cambrian period, and is itself divided into three eras of Geological time, the Hadean, the Archean and the Proterozoic. The time frame encompassed by the “Pre-Cambrian” includes everything from the formation of the Earth 4600 million years ago, to the start of the Cambrian period 542 million years ago.

The Hadean era is the eldest era, and spans from the formation of the Earth (4600ma) to the beginning of the Archean era 3800ma. No rocks survive from the Hadean era, but it is theorised that at this time the surface of the Earth was a giant sea of lava with huge volcanoes, and a highly toxic (to us) atmosphere made of carbon dioxide and water vapour. Any rocks that did manage to form on the surface would have been quickly covered by new lava flows, or blasted away by impacts from space. It is believed that during the Hadean era an asteroid as large as the planet Mars smashed into the Earth and in the process created the moon as part of the “splash”! Rocks that have a date from this era are rocks that have fallen from Space and Moon Rocks.

Links for the Hadean era:
http://www.peripatus.gen.nz/paleontology/Hadean.html
http://www.fossils-facts-and-finds.com/hadean.html


Image Credit; (http://bullet-magnet.deviantart.com/art/Planet-Icarus-Erebosian-Eon-48325388)



No comments:

There was an error in this gadget