Geological Time Scale Flashcards
How old is Earth
4.55 billion years old
How are Eras defined?
Based on the appearance or disappearance of different life forms found in fossils.
How long was the Precambrian Era?
4 billion years
How long was the Paleozoic Era
300 million years
How long was the Mesozoic Era
185 million years
When did the Cenozoic Era start
65 million years ago
List key moments that occurred in the Precambrian Era
- Rodinia (the first continent) formed
As well as the appearance of:
-Prokaryotes (cells without a nuclei) and bacteria capable of photosynthesis
-Eukaryotes (cells with a nucleus), worms, soft coral and jellyfish
-Ediacaran fauna; animals capable of digesting and reproducing
List key moments that occurred in the Paleozoic Era
-Earth separates into four continents
Appearance of:
-animals with a spine and land plants
-jawed fish
-ferns
-first amphibians (life gets out of water)
-Appearance of conifers and small reptiles
1) Cold climate causes mass extinction to which half of animals disappeared
2) Major extinction due to various events caused 70% of all marine life to vanish
3) Largest mass extinction caused by glaciation, volcanic eruptions and destruction of ozone layer results in the disappearance of 96% of marine species and 75% of land species.
List key moments that occurred in the Mesozoic Era
-Warm climate favoured large reptiles and dinosaurs
-Appearance of birds, small mammals and flowering plants
1) Mass extinction due to a meteorite impact or volcanic eruption caused 50% of marine life to vanish
2) Mass extinction due to a meteorite impact in Yucatan, Mexico, causing the death of the dinosaurs
List key moments that occurred in the Cenozoic Era
-Era begins with a long cooling and drought period
-Mammals continue to thrive with the appearance of megafauna, primates and hominids
-Some extinctions have happened caused by hunting, fires and diseases
