Paleozoic+Era

Paleozoic Era
 The next 570 million years are divided into three eras. The longest of these is the Paleozoic era. During the 345 million years of this era, Canada's landforms continued to take shape. Sediments were moved by rivers and deposited in the shallow seas that surrounded the Shield. Over millions of years, these sediments were compressed into sedimentary rock. Today these rocks form the bedrock of parts of every province.

 Geologists believe that North America was located near the equator during the early part of the Paleozoic era, over 400 million years ago. Organisms that eventually produced the great oil and gas deposits of western Canada lived in shallow seas around the ancient Canadian Shield. Huge swamps grew in the warm climate of this tropical location. The swamps eventually produced the coal bearing rocks of Nova Scotia. Sediments deposited in the Paleozoic era also produced the salt beds of southwestern Ontario.

1. What was the most important geological event of the Paleozoic era?

2. Geologists believe that Canada was located closer to the equator during the early part of the Paleozoic era. Why has this tropical location been important to Canada?

 About 300 million years ago, the continents collided to form the supercontinent of Pangaea. This collision caused the eastern part of North America to crumple up and form the Appalachian Mountains.

 At the beginning of the Paleozoic era, living organisms existed only in the seas. For the first time, organisms with shells appeared. Later, simple plants appeared on land and eventually forests of trees developed. As time passed, more complex organisms such as fish, insects, and amphibians began to evolve. Amphibians were the first animals to live on land. Remains of these Paleozoic organisms are now found in sedimentary rocks as fossils. Fossils help scientists to estimate the age of the rock in which they are found.

3. Based on the fossil evidence, what life forms existed during the Paleozoic era?

 The division between the Paleozoic and the Mesozoic eras was a time when many plant and animal species became extinct. Half of the fossil groups of organisms found in the rocks of the late Paleozoic era are missing in the rocks of the early Mesozoic era. During the past 600 million years, there have been at least five such mass extinctions. During each of these, many of the earth's species disappeared and new and greater numbers of species appeared. The greatest extinction occurred in the late Paleozoic era when at least 80% of life in the seas became extinct and land plants and animal species disappeared in large numbers. The cause of this extinction is not clear but it could be related to the formation of Pangaea and related climate changes.

4. What event marks the division between the Paleozoic and Mesozoic eras?