1. Chapter 13
Earth’s History
Who is Stan Hatfield and Ken Pinzke

2. 13.1 Precambrian Time: Vast and Puzzling
Precambrian History
13.1 Precambrian Time: Vast and Puzzling
The Precambrian –
encompasses immense geological time
From Earth’s distant beginnings 4.56 billion years ago until the start of the Cambrian period, over 4 billion years later.
 Precambrian Rocks
• Shields - large, relatively flat expanses of ancient metamorphic rock within the stable continental interior.
• Most of our knowledge about Precambrian rocks comes from ores mined from shields.

3. Geologic Time Scale
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4. Remnants of Precambrian Rocks
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5. 13.1 Precambrian Time: Vast and Puzzling
Precambrian History
13.1 Precambrian Time: Vast and Puzzling
 Earth’s Atmosphere Evolves
• The original atmosphere - gases like those released in volcanic eruptions today—water vapor, carbon dioxide, nitrogen, and several trace gases, but NO OXYGEN.
• Later on, primary plants evolved using photosynthesis, and oxygen was released.
(Iron mopped up a lot of this early oxygen)
• Oxygen began accumulating in the atmosphere about 2.5 billion years ago.

6. 13.1 Precambrian Time: Vast and Puzzling
Precambrian History
13.1 Precambrian Time: Vast and Puzzling
 Precambrian Fossils
• The most common Precambrian fossils are stromatolites.
• Stromatolites – distinctively-layered mounds or columns of calcium carbonate. They are not the remains of actual organisms but are the shell material deposited by algae called diatoms
• Many of these ancient fossils are preserved in chert—a hard dense chemical sedimentary rock.

7. 13.2 Paleozoic Era: Life Explodes
Early Paleozoic
13.2 Paleozoic Era: Life Explodes
Following the long Precambrian, the most recent 540 million years of Earth’s history are divided into three eras:
1) Paleozoic(oldest)
2) Mesozoic (middle)
3) Cenozoic (newest).

8. 13.2 Paleozoic Era: Life Explodes
Early Paleozoic
13.2 Paleozoic Era: Life Explodes
 Early Paleozoic History
• During the Cambrian, Ordovician, and Silurian periods, the vast southern continent of Gondwana encompassed five continents (South America, Africa, Australia, Antarctica, and part of Asia).

9. Gondwana and the Continental Landmasses
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10. 13.2 Paleozoic Era: Life Explodes
Early Paleozoic
13.2 Paleozoic Era: Life Explodes
 Early Paleozoic Life
• Life in early Paleozoic time was restricted to the seas.
- Life in the Paleozoic is split into 7 periods:
- Cambrian
- Ordovician
- Silurian
- Devonian
- Mississippian
- Pennsylvanian
- Permian
Invertebrates
Fishes
Amphibians

11. Life in the Ordovician Period
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12. 13.2 Paleozoic Era: Life Explodes
Late Paleozoic
13.2 Paleozoic Era: Life Explodes
 Late Paleozoic History
• Laurasia is the continental mass that formed the northern portion of Pangaea, consisting of present-day North America and Eurasia.
• By the end of the Paleozoic, all the continents had fused into the supercontinent of Pangaea.

13. Late Paleozoic Plate Movements
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14. 13.2 Paleozoic Era: Life Explodes
Late Paleozoic
13.2 Paleozoic Era: Life Explodes
 Late Paleozoic Life
• 400 million years ago, plants adapted to survive at the water’s edge and began to move inland, becoming land plants.
• The amphibians rapidly diversified because they had minimal competition from other land dwellers.

15. Armor-Plated Fish
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16. Model of a Pennsylvanian Coal Swamp
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17. 13.2 Paleozoic Era: Life Explodes
The Great Paleozoic Extinction
13.2 Paleozoic Era: Life Explodes
 The world’s climate became very seasonal, probably causing the dramatic extinction of many species.
 The late Paleozoic extinction was the greatest of at least five mass extinctions to occur over the past 500 million years.