Earth Systems 3209

1. Earth Systems 3209 Reference: Chapters 6, 8; Appendix A & B Unit: 2Historical Geology

2. Unit 2: Topic 1.1 Uniformitarianism “vs” Catastrophism Focus on . . . • recognizing that Uniformitarianism is a fundamental principle of geology and contrast this principle with catastrophism.

3. Historical Geology • Science is the investigation of ideas. Throughout history, scientific ideas (paradigms) change as new evidence is discovered regarding scientific models and theories. • These changing ideas were demonstrated throughout geologic history. One notable change that formed the framework for geologist is the movement from Catastrophic ideas to one of uniformity, hence the birth of the principle of Uniformitarianism. Text Reference: pages 5-6

4. Doctrine of Catastrophism: Catastrophists thought that Earth’s physical features (mountains, canyons, and almost all landforms) formed by sudden spectacular events (catastrophes) produced by unknowable causes that no longer operate and can not be explained by nature. (James Usher) These ideas attempted to fit the rate of change of Earth’s processes into a relatively young aged Earth. These scientist thought Earth was millions and not billions of years old. This is not to say that catastrophic events do not occur today, tsunamis, earthquakes, volcanic eruptions, etc.

5. Principle of Uniformitarianism: • One idea that helped scientist better understand the processes acting on Earth is the idea ofUniformitarianism. This idea was first recognized by a Scottish Geologist named James Hutton. • After years of studying land forms and rocks, Hutton came to the conclusion that, “ the present is the key to the past”and “that, the physical, chemical, and biological laws that operate today to shape Earth also operated in the past.”

6. Example 1: Question:How would the ideas of Catastrophismand Uniformitarianism explain the formation of the Grand Canyon?

7. Example 1: Question:How would the ideas of Catastrophismand Uniformitarianism explain the formation of the Grand Canyon? Catastrophist: • Sudden event • Unknowable causes • Unexplained • Short period of time

8. Uniformitarianist: • Gradual change • Uniform processes • Long period of time Example 1: Question:How would the ideas of Catastrophismand Uniformitarianism explain the formation of the Grand Canyon?

9. Example 2: Questions:Which suggests that major Earth features are the result of sudden disasters of unknowable causes in Earth’s past?(A) catastrophism (B) creationism(C) fundamentalism (D) uniformitarianismWhich states that the basic laws of nature have remained unchanged since Earth was created?(A) catastrophism (B) correlation(C) superposition (D) uniformitarianism

10. Example 3: Question:Based on the information below, answer the question that follows; Identify and explain a concept that scientists could use to support the idea suggested in the above quotation. “The Earth has been covered by giant combinations of continents, called supercontinents, many times in its past, and it will be again one day in the distant future. The next predicted supercontinent . . . may form when the Americas and Asia both drift northward to merge, closing off the Arctic Ocean . . . .” Charles Q. Choi, Our Amazing Planet

11. Example 3: • Question:Identify and explain a concept that scientists could use to support the idea suggested in the above quotation. • The idea can be supported by the concept of uniformitarianism. Uniformitarianism explains that the same geologic processes that were occurring on Earth in the past are still occurring today and will continue to occur in the future. • Earth has experienced tectonic forces which were responsible for the formation and destruction of supercontinents in the geologic past. Since these same forces are still occurring today and will continue to occur in the future, then it can be concluded that there will once again be another supercontinent in the future.

12. Your Turn . . . Take the time and complete the following questions . . .(Solutions to follow) Question: With the aid of a specific example, explain how uniformitarianism can be used to understand past catastrophic events.

13. Solutions . . . Questions: With the aid of a specific example, explain how uniformitarianism can be used to understand past catastrophic events. • The principle of uniformatarianism states that processes that acted on Earth in the past,are still actingon Earth today and will continue in the future. • Catastrophic events which occur on Earth today, for example, earthquakes, are caused by the same processes that caused earthquakes in the past. • These forces associated with plate tectonics cause present day earthquakes and are thought to be responsible for causing earthquakes in the past.

14. Another Question and Solution: Two hikers sit together on a hilltop overlooking a steep-sided river valley. One hiker explains its formation using uniformitarianism while the other uses catastrophism. Summarize each hiker’s explanation of how the valley formed. A. The hiker that follows an uniformitarianism view would suggest that the valley formed over an extremely long period of time (perhaps millions of years) and was formed by physical forces, such as erosion and weathering, that have affected and shaped Earth for millions of years. In comparison, a hiker that follows a catastrophic view would suggest that the valley formed over a relatively shorter period of time and was formed by some unexplainable, sudden event commonly called a catastrophe, for example an earthquake, etc....

15. Uniformitarianist: • Gradual change • Uniform processes • Long period of time Summary . . . Overview of Points covered: Catastrophist: • Sudden event • Unknowable causes • Unexplained • Short period of time