Before you start this assignment, it is important that I introduce the some new ideas. Read on for important information.

We have looked at the Earth’s Biosphere. Remember, the biosphere is the area in, on, and around the Earth that contains living things. Now we are going to investigate the geosphere or Earth’s Geologic System.

Geology has to do with rocks, rock cycles, and rock formation. We use the word GEOSPHERE to describe all systems and parts of systems dealing with the solid portion of the Earth. This includes rocks of all sizes, the Earth’s crust and the inner parts of the Earth (some of which are not solid!).

The other Earth systems have names as well. In the previous assignments you studied the BIOSPHERE. The biosphere encompasses all life on Earth. In subsequent quarters you will study the ATMOSPHERE and the HYDROSPHERE as well. The atmosphere describes the Earth’s gases, particularly those that form a “blanket” covering the Earth’s surface. The hydrosphere refers to the Earth’s water and all of its associated systems.

There you have it! The four major Earth systems: biosphere, geosphere, atmosphere, and hydrosphere. Now we will begin our exploration of the geosphere.


Many people view science as cold, hard facts that are indisputable. In reality, there is a lot more to science than cold, hard fact. In fact, many of science facts are not cold, hard truths. Scientific knowledge often is the best explanation we have at the time for what we see. As we learn more and are better able to see things, scientific explanations may, and often do, change. Science claims are tentative.

The goal of science is to produce a systematized body of knowledge that has explanatory and predictive power. We want to understand things. We seek understanding by observing natural phenomena but, because scientists are human (believe it or not, science teachers are human also!), their observations are influenced by their prior knowledge, experience, and beliefs. Also, because they are human and because science is always seeking new understandings, the problems that science investigates, the methods they use, and the way they interpret evidence changes from time to time.

Just what does all this have to do with plate tectonics you ask? Plate tectonics is a theory that has explanatory and predictive powers. It has been developed and modified over the centuries by scientists whose observations and explanations were influenced by their personal beliefs and prior knowledge. The story of the development of the theory of plate tectonics is a story of science in action.

Science in action---this is the object of our study. In this assignment you will see that scientists do not always agree, that explanations change as more information becomes available, that creative thinking and imagination are vital to scientific endeavors, and that science produces a growing, changing body of knowledge. In the process, you will also learn about the theory of plate tectonics. Sounds fun, doesn’t it?


· Go to the Plate Tectonics Internet site:

· Study the information on plate tectonics. At the bottom of each screen, click on NEXT SECTION until you reach the screen on types of plate margins.

· Fill out the following worksheet as you go through the screens.

· The following web site also has some excellent, easy to understand information on plate tectonics: ?

PLATE TECTONICS WORKSHEET--Use complete sentences to answer the questions.

1. What is the theory of continental drift?

2. Who proposed the theory? When?

3. What scientific data was used to support the theory of continental drift? Identify and explain at least four types of evidence.

4. What were the problems with the theory of continental drift?

5. Imagine that you are a scientist living at the time that Wagner proposed his theory. What might you have thought of his theory? What biases might you have had that would influence your acceptance of the theory?

6. What proposed explanations overcame the problem of how the continents moved?

7. How does the presence of ocean ridges and trenches support the theory that the continentals move?

8. How does sea floor spreading support the theory that continentals move?

9. How was sea floor spreading tested as a hypothesis?

10. How does the fossil record support the theory of plate tectonics?

11. How does the distribution and pattern of earthquakes support the theory?

12. In your own words, state the theory of plate tectonics.

13. How does the development of the theory of plate tectonics illustrate the changing nature of scientific knowledge?

14. How was the scientific method used to establish the theory of plate tectonics?

15. In your mind, what is a theory? Can theories change? Who makes theories? What has to happen to a scientific explanation for it to become a theory?


Send me your answers to the worksheet questions. If your answers are written in complete sentences, are accurate, and reflect good thinking then you will receive a good grade.


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