Canada's+Geologic+History

CANADA'S GEOLOGIC HISTORY
 Canada's amazing physical diversity is largely the result of the country's geologic development. Plate tectonics helps to explain part of Canada's geologic history, but there are other forces that come into play. The earth's physical landscape is also partly the result of conflict between forces that build the land higher and those that wear it down. Land that is violently pushed upward by great forces within the earth may form mountains. Mountains, in turn, are slowly and continuously worn down by wind, rain, running water, and ice. This wearing down is called erosion.

 At different times and in different places, one force has been stronger than the other. This conflict bas taken place over hundreds of millions of years, and forms the story of the earth's geologic history. How can we find out about the earth's early physical history? One approach is to carefully analyze landforms, rocks, and fossils.

 How can we imagine how old the Earth is, when it is estimated to have formed about 4 600 000 000 years ago? Here is a way to help you understand the passing of geologic time. Divide your age into a million years. This will tell you how many of your lifetimes equal one million years. For example, if you are 15, you would have to live your life approximately 66 667 (1 000 000 / 15) times before you would live a million years. How many times would the length of your life fit into the earth's lifespan of 4 600 000 000 years?

To make geologic time easier to understand, geologists have divided the earth's history into four time periods called eras. Each era represents a time of major sediment deposition and earth movement. While researchers do not all agree on their findings, the account you will be presented with is widely accepted. You may recognize some of the names, as at least one has been associated closely with the reign of the dinosaurs.

Activity
1. Summarize! Your job is to summarize each paragraph into no more than 2 points. Remember, when summarizing you are breaking things down into what is important. 2. Find a definition online or in a dictionary of erosion, fossil, and deposition. Does knowing the definition of the word change your understanding of the material?