Download GEOLOGIC TIME

GEOLOGIC TIME
ESRT PAGES 8 and 9
AGE OF EARTH
• 4.6 Billion Years old = 4600 Million Years
old
• MYA = millions of years ago
GEOLOGIC TIME
• Based on fossil evidence and mass
extinctions
• Life forms have evolved over time
• 4 MAJOR ERAS
1. PRECAMBRIAN
• Longest era
4.6 billion years to 544 million years ago,
longest geologic era,
lasted about 4 billion years
• No fossil record – WHY?
a. Most rocks were non-sedimentary
because the earth was still cooling
b. Small organisms with no hard shells
Ending of Precambrian Era sees a sudden
explosion of life due to evolution of
atmosphere
What process added oxygen to the
atmosphere?
photosynthesis
2. PALEOZOIC
• 544 million years to 251 million years ago
• Invertebrates
• Fish, amphibians, vertebrates
• land plants first appear
At the end of Paleozoic
• massive climate change and mega
volcanoes that erupted for centuries
• Massive release of CO2 into atmosphere
• Temps on planet warmed
• Mass extinction of trilobites, eurypterids,
fern-like plants and many insects
3. MESOZOIC
• 251 million years to 65 million years ago
• Dinosaurs
• Earliest Birds and mammal
• Extinction of dinosaurs
• 63 Millions years ago
At end of Mesozoic
• Asteroid impact
• Vast cloud of searing vapor and debris
raced over continents incinerating
everything in its path
• Pulverized rock was ejected
• Enough heat was generated to broil
surface of planet
• Lots of sulfur in the air
• All dinosaurs became extinct as well as
many, many other organisms
• Evidence of impact crater is in the Yucatan
peninsula in Mexico
4. CENOZOIC
• 65 million years ago to present
• Modern plants and animals
• Last 2 million years - age of man,
dominated by glaciation