Geo Time Scale Instructions
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Project AstroBio The History of the Earth and the
Evolution of Life: Introduction: The Geologic Column took many years and much debate to develop in the 19th and 20th centuries. The end result is a chronological progression of life’s evolutionary milestones through all of geologic time from Earth’s origins to the present. Major divisions in the column are based upon either the rise to prominence of some new form of life, or a mass extinction of many forms of life. For example, the mass extinction we know best, the extinction of the dinosaurs (and 50% of all other species), took place 65 million years ago, at the end of the Cretaceous and the beginning of the Tertiary Periods. Thus a major event in the evolution of life has become a major delineator of time in the geologic record. In this activity, students will create a scale model of the Geologic Column, including the major events in the evolution of life on Earth. It can easily be adapted for any level within grades 4-12. Older students can work out the math, do research, and be more creative in designing the scaled time line, whereas it is more of a demonstration for younger students. In either case students will come away with an appreciation for the vast expanse of time covered by the Earth’s history relative to what we think of in our lives as a “long time”. Activity: The scaled timeline is based on a simple scale -- 4.56 billion years of Earth history will be condensed to a distance of 4.56 meters of adding machine tape. This can be done in a classroom using the tops of desks that are pushed together, or a length of classroom or hallway floor. Upon this record we will place time markers at certain intervals, as well as objects and images that represent major developments in the evolution of life. When all of this is laid out before us, we will come to a startling visual conclusion, namely how little of the Earth’s history has been involved with complex life (organisms with more than one cell). Materials Needed:
Instructions: 1. Tape together lengthwise, the 3 pages of The Geologic Column & Evolution of Life provided with this activity. This is the source of the information to make your scaled timeline. 2. Measure out a strip of adding machine tape 4.56 meters long. 3. Select one end of the tape to represent the Present. Beginning at that end, mark off each billion years according to the scale below, then subdivide and mark each billion years into 10-million year intervals: 4.56 billion years = 4.56 meters 1 billion years = 1 meter 10 million years = 1 cm 1 million years = 1 mm 4. Move to the opposite end of the tape. Beginning with the oldest event, mark off all of the important events in Earth’s history and the evolution of life as shown Geologic Time Scale & Evolution of Life. 5. Place the appropriate items and images on the scaled timeline to graphically illustrate the major events in the history of the earth and the evolution of life. Variations on this Activity: This scale can also be easily adapted for outdoor use, for example letting 4.56 billion years be represented by 456 meters (6-8 city blocks). This is an even more startling scale, and further allows one to actually “see” 1000 years, which is 0.1 mm! One can also add to the timeline a few astronomical and cosmological milestones in the history of the Universe, which extends back to the Big Bang at 13.7 billion years ago, three times longer than the Earth’s age. Other Methods of scaling the History of the Earth and the Evolution of Life: The above is but one method of producing a “scale model” of geologic time and evolution. Other methods to represent the 4.56 billion years involve a 24-hour clock, a one-year calendar, or a novel use of dots on a sheet of paper combined with a tower of reams of paper. 24-hour clock One-year calendar Stack o’ paper Credits: 1. The 4.56 billion years = 4.56 meters of adding machine tape activity was drawn from the exercise, “Lab 1, The History of the Earth”, from Laboratory Manual for Physical Geology, by Baer, Baer, and Whittington, Highline Community College, Washington, 1998. 2. The Stack o’ Paper activity was drawn from the exercise, “As Time Goes By”, origin unknown. |
