GEOLOGICAL PERIODS 
CHRONOLOGY OF EARTH’S HISTORY 
Cenozoic or Recent Era Began about 
Quaternary period 
Recent Epoch 50,000 b. c. 
Pleistocene or Glacial Epoch 1,000,000 B. c. 
Tertiary Period 
Pliocene Epoch 
Miocene Epoch 
Oligocene Epoch 
Eocene Epoch 
Paleocene Epoch 
Mesozoic or Medieval Era 
Cretaceous Period 
Jurassic Period 
Triassic Period 
Paleozoic Era or Antiquity 
Permian Period 
Pennsylvanian Period 
Mississippian Period 
Devonian Period 
Silurian Period 
Ordovician Period 
Cambrian Period 
The Proterozoic Era 
The Archeozoic Era 
7,000,000 b. c. 
19,000,000 b. c. 
35,000,000 b. c. 
55,000,000 b. c. 
short period intervening 
95,000,000 B. c. 
155,000,000 b. c. 
190,000,000 b. c. 
Earth 
215,000,000 B. c. 
250,000,000 b. c. 
300,000,000 b. c. 
350,000,000 b. c. 
390,000,000 b. c. 
480,000,000 b. c. 
550,000,000 b. c. 
Certain Archean works 
have been estimated to 
be 1,500,000,000 years 
old. 
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