Chapter 2, Section 3 – Unit A Science 8 Messana

 What did you decide was more useful…tree rings or ice cores?  Why?

 Geologic Time Scale – a timeline of Earth’s History divided into periods of time by major events or changes on Earth What do we call these major events or changes?

Catastrophic Events – events that cause major destruction or change life completely Examples:  Mass extinctions  Ice Ages  Meteors  Major volcanic eruptions

 1. Hadean  2. Archean  3. Proterozoic  4. Phanerozoic  #1-3 make up Precambrian Time  Eons -> Eras -> Periods -> Epochs  Change in name is due major geologic or climatic events!!

 90% of Earth’s history  Lasted nearly 4 billion years of Earth’s 4.6 billion years  Volcanic ash & dust ->clouds formed ->rain  Single-celled micro-organisms in ocean at end  No animals  No plants

 544 million years ago – present  Explosion of Life!  3 Eras: ◦ Paleozoic Era – “Age of Amphibians” ◦ Mesozoic Era – “Age of Dinosaurs” ◦ Cenozoic Era – “Age of Mammals”

 544 mya – 248 mya  All life in ocean until end  Fish developed  Reptiles, Insects, Ferns developed – moving life onto land at end  Ends with a Mass Extinction (from a meteor strike?)– kills 90% of all ocean species

 248 mya – 65 mya  Dinosaurs rule!  Small mammals, birds, flowering plants  Ends with Mass Extinction due to meteor strike off Mexico ->dust cloud blocked sunlight, killed plant life and affected food chain

 65 mya – Present  Large warm-blooded mammals, modern birds, flowering plants  Animals developed migration techniques  Tertiary Period  Quaternary Period = last 2 million yrs ◦ Ice ages ◦ 1 st modern human fossils = 100,000 yrs old ◦ Humans are ? seconds of 12 hour clock!! :0

 Earth is constantly changing due to the same basic forces  EX:Slow = erosion, plate movement Fast = volcano, earthquake