To me “curiosity killed the cat but satisfaction brought him back” can best describe why man has and continues to learn more about the world we live in. An example would be people not listening to the church teaching of the earth being about 6,000 years old and not changing. James Hutton was one such person. His observations of extinct volcanoes, igneous rock intrusion (prevailing belief at that time was all rocks were formed by deposition),rate of erosion of an ancient wall which was built in 200 AD that did not show effects of erosion made him realize that it would take millions of years for a mountain to erode and finally his observations of rock layers not all being horizontal gave more evidence of a dynamic earth. It was observed that fossils of the same organism on continents thousands of miles apart, glacial deposits in tropical latitudes, same rock structures in mountains separated by oceans, and the shape of the continents. Alfred Wegner put these continents together and called it Pangea which means all land. His idea did not get support because at that time no one could explain what forces could move these large masses of land.
We now have the information to answer that question. We know the earth’s surface consist of plates surrounded by mid-ocean ridges and trenches. These plates float on a layer of the mantle called the Asthenosphere. A way of showing how this operates is to place some wood blocks together in a pan containing corn syrup. Heat the corn syrup and have the student observe the motion of the wood blocks due to the convection movement within the corn syrup. The movement of plates result in their coming into contact with other plates. When this happen they may:
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1. Diverge—drift apart
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2. Convergent—come together
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3. Transform—slide/grind past
The above movements are important as they have an impact on the climate of an area. For example, mountain building has a bearing on the amount of moisture and area will receive, drifting apart changes their latitude which influences the amount of solar radiation and materials escaping into the atmosphere from these activities affect the atmospheric composition. Look at these fig. 5 showing the positions of the earth’s landmasses in the past, present and future.
