Geologic Time

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Geologic Time
Geologic Time
A. Earth ≈ 4.6 Billion Years Old
1.
4.6 Billion = 4,600,000,000
2. Most Geologic Time is divided
into eras and periods
B. Precambrian Time = 88% of Earth’s History
1. Precambrian
Earth: lava
flowed over
the surface –
building the
continents
2. First Life? Bacteria found in rocks
from 3.5 Billion Years Ago (BYA)
3. About 2.5 BYA, bacteria
started using sunlight to
make their own food.
C. The Paleozoic Era
1. began ~544 Million Years
Ago (MYA)
2. Most
Paleozoic
animals were
invertebrates
Cambrian Species
3. After ~300 million years, about 95%
of Earth’s species DIE due to…
DRASTIC climate change caused by
Pangaea forming (about 260 MYA)
D. The Mesozoic Era
1. began ~245 MYA
2. Mesozoic = Age of Dinosaurs (or Reptiles)
Mesozoic Era
3. Dinosaurs ruled the Mesozoic, but the
first mammals also appeared in that era.
4. Dinosaurs lived from ~225 MYA to ~65 MYA
5. About 180 million years after the start of the
Mesozoic era, a massive impact filled the sky
with debris and changed the climate
E. The Cenozoic Era
1. began ~65 MYA and
continues today.
2. Cenozoic = Age of Mammals
3. Last Ice Age was ~10,000 years ago

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