Geological Time

Geology deals with vastness of time that is far outside human experience. Our common experience of time, and our ancestors' experiences that shaped our brain's evolution, span intervals from a moment, to a day, to a season, to a year, to a lifetime. Geologists, in contrast, deal with thousands to millions of years, up to the 4.5 billion year age of the Earth. This vastness of time is central to geological thought, because it allows time for imperceptibly slow processes to effect monumental changes. Given enough time, erosion levels mountains. Given enough time, natural selection produces new species. Frodeman (2003) argues that understanding the brevity of human existence relative to the span of Earth history requires an "innovation in our sense of reality."

In addition, time is a clue to causality in geology. If it can be shown that A happened before B, then A can have caused or influenced B, but B cannot have caused or influenced A. And finally, rate is important because it is a clue to the energy budget of the causative process; a process that moved a cubic kilometer of material in an hour is a profoundly different phenomenon than a process that moved a cubic kilometer of material in a million years.

We wish to know:

• How do humans build on our experiential concept of time to deal with temporal scales of thousands to billions of years? What distortions are introduced into a learner's view of earth history and process if the immenseness of geological time is not grasped?
• What is the role of narrative, of analogy (Frodeman, 1995), and of representation in helping people understand unfamiliar times and time spans?
• How do learners make the conceptual leap from observable processes (e.g. convection of cream in a cup of coffee at a rate of cm/s) to processes that are too slow to observe (e.g. convection of the Earth's mantle at a rate of mm/yr)?
• By what sequence of understandings does a learner come to accept that a landscape that looks static according to the standards of our life experiences is actually dynamic, undergoing constant change, but at a rate too slow for us to see?
• What is necessary for a learner to accept as "known" an event or sequence of events that happened when no humans were there to observe it?
• What is the relationship between a learner's understanding of time and causality? What is the relationship between a learner's understanding of the rate of earth processes and the energy of the formative processes?

Researchers have begun to develop instruments and methodologies to probe learner's knowledge of, interest in, and ability to reason about geological time. For example, Trend (1998, 2000, 2001, 2002) used card sorting, questionnaires, concept mapping, group discussions, and responding to objects, to explore what students and teachers know about the sequence and timing of events in geological history. He found that children cluster geologic events into just two categories ("extremely ancient" and "less ancient"). Their assignment of geo-events to these categories is generally accurate, but there is confusion over the relative timing within each time cluster (Trend, 1998). Dodick and Orion (2003a, 2003b) have developed an instrument, the Geological Time Aptitude Test, to probe students' ability to employ diachronic thinking in a geological context. "Diachronic" refers to the study of the development of something through time (Montagnero, 1996), for example, the ability to determine the sequential order of stages, or to identify precursor/successor linkages between events. They found that many students found such tasks difficult, that diachronic thinking continues to improve with age in the absence of instruction among 11 th and 12th graders, and that study of geology accelerates the acquisition of diachronic thinking skills even in a non-geological scenario.

Cited References

Dodick, J. and N. Orion (2003a). Measuring student understanding of geological time. Science Education, 87, 708-731.

Dodick, J. and N. Orion (2003b). Cognitive factors affecting student understand of geological time. Journal of Research in Science Teaching, 40, 415-442.

Frodeman, R. (1995). Geological reasoning: Geology as an interpretive and historical science. Geological Society of America Bulletin, 107, 960-968.

Frodeman, R. (2003). Geo-Logic: Breaking Ground Between Philosophy and the Earth Sciences, State University of New York Press, 159 p.

Montangero, J. (1996). Understanding Changes in Time. Taylor and Francis, London.

Trend, R. D. (1998). An investigation in into understanding of geological time among 10- and 11-year-old children. International Journal of Science Education, 20, 973-988.

Trend, R. D. (2000). Conceptions of geological time among primary teacher trainees, with reference to their engagement with geosciences, history and science. International Journal of Science Education, 22, 539-555.

Trend, R. D. (2001). Deep time framework: A preliminary study of U.K. primary teachers' conceptions of geological time and perceptions of geoscience. Journal of Research in Science Teaching, 38, 191-221.

Trend, R. D. (2002). How Important is Deep Time? Unpublished m manuscript. Downloaded May 16, 2006, from www.cgu.org.tw/2004jga/dach/paper/07/07-O-01.doc