GEOL 1001 Chapter : Chapter 11 - Geologic Time Scale
Document Summary
Hadean eon (4. 57 - 3. 85 ga) (cid:12254) (cid:12254) Archean eon (3. 85 - 2. 5 ga) (billion) (cid:12254) Ma c crust gets melted to produce island arcs, hotspots which then gets partially melted to turn into felsic crust. Felsic crust begins to collide with each other. 85% of continental crust formed during this time. This is the time period when we get our rst signs of life. Stromatolites - microbial mats that form as a mound (cid:12254) Atmosphere was still unbreathable - starting to get o2. Proterozoic eon (2. 5 - 542 ma) (cid:12254) (cid:12254) (cid:12254) It is called rodinia - 800 to 600 million years ago, the continents readjusted and it became known as (pannotia) These have a nucleus that is more complex. First abundant fossil bed - 1. 2 billion years ago, these animals don"t move. These are one celled bers that give them mobility. Atmosphere at about 2. 4 billion years ago. (cid:12254) Iron in ocean precipitated because of the oxygen.
