Geological Eras

Geological Eras

1. Precambrian Era

   • • lasted 4 billion years (4.6 billion years ago-579 million years ago) • represents 87% of Earth's history
   • Geological Events
     • Only part of Canada that existed was the Canadian Shield
     • The Shield consists of mainly igneous and metamorphic rocks
   • Biological Events
     • Single-celled organisms; fossils of algae found in rocks, dating to the middle of this period

2. Palaeozoic Era

   • Biological Events
     • Tropical locations = tropical climates = swamps on the edges of the shallow seas of the Shield
     • Living organisms developed in shallow seas and swamps
       • First organisms with shells in the sea; first plant in land
       • Then came fish in sea; amphibians on land
         • Fossils of these organisms found in rocks
       • *Mass extinction is the dividing line between Palaeozoic Era and Mesozoic Era.
         • Mesozoic Era
           • Ends with mass extinction. More than 1/2 of the plant and animal species became extinct.
             • Theory is that it was caused by a collision with an asteriod
         • End of the Palaeozoic Era saw at least 80% of sea life disappear and many land plants and animals as well -- cause is unknown-- break up of Pangaea, climate change???
   • Geological Events
     • North America continues to take shape; sediments moved by the rivers and deposited in shallow seas around the Shield
       • (These were compressed into sedimentary rocks and formed bedrock (solid rock beneath the soil))
     • 300 million years ago, continents collided to form Pangaea
       • Caused the Appalachians to form

3. Mesozoic Era

   • Biological Evenst
     • Climate is still warm
       • Reptiles and dinosaurs roamed large swamps and inland seas east of the Rockies (Alberta)
       • Sea creatures (coral reef) and plants; vegetation in swamps --> as they die, they are covered by sediments and later become oil and coal
   • Geological Evenst
     • Beginning of the break up of Pangaea
       • Beginning to form Rocky Mountains (folding) as the Pacific Plate collided with the N. American Plate
       • New layers of sedimentary rocks

4. Cainozoic Era

   • Biological Evenst
     • Mammals (including humans) dominate
       • Effects on landscape -> dams changed river systems
       • Effects on biology -> extinction of animals
   • Geographical Events
     • Final changes to Canada's landforms
       • Collision of the Pacific and N. American plates caused uplifting to form the Coast Range Mountains; Rockies continue to form
       • Inland seas disappear as land begins to rise
     • Glaciation
       • 4 periods of glacial activity in the last 2 million years (glaciers formed and retreated)
       • Weight caused them to scrape along the surface; transported material, rounded mountains (the Appalachians) and carved lakes