Constructing Deep Time Knowledge
Doug Lombardi, University of Nevada, Las Vegas
Knowledge about deep time, sometimes referred to as geological time, is essential to understanding several topics covered in science courses, including biological evolution, stellar life cycles, cosmology, plate tectonics, and global climate change. However, understanding deep time has proven difficult for students (Dodick & Orion, 2003; Libarkin, Anderson, Science, Beilfuss, & Boone, 2005; Prather, 2005; Trend, 2001a, 2001b). Basic conceptions of time may begin forming as early as infancy (Mandler, 2008), but having fundamental temporal conceptions does not necessarily mean that individuals will naturally develop a concept of deep time. Furthermore, the development of deep time understanding may involve coordinating temporal conceptions with other cognitive processes. For example, Dodick and Orion (2003) examined the capacity of students to use an "active logical understanding of geological time" (p. 418). Dodick and Orion found that, in addition to other cognitive abilities, students must possess the "basic principles of diachronic thinking" (p. 436) in order to describe past geological systems. Specifically, diachronic thinking would be involved in understanding how objects and processes change over time, and specifically in the case of deep time, how changes occur over very long time periods. Student would therefore have to coordinate their understanding of time and diachronic thinking when encountering scientific phenomena involving long-term transformations. Instruction designed to facilitate this coordination could potentially strengthen students' deep time understanding, as well as their scientific knowledge.
Educational research about student understanding of deep time has generally focused on transformations over time periods from hundreds of millions to billions of years (see, for example, Dodick and Orion, 2003; Trend 2001a, 2001b). However, a recent study by Lombardi and Sinatra (2010) shows that deep time understanding contributes to understanding about transformations on the order of decades to hundreds of thousands of years (i.e., the time periods associated with climatic events). Lombardi and Sinatra (2010) specifically found that greater knowledge of deep time and increased plausibility perceptions of human-induced climate change provide significant explanation of variance in student understanding of weather and climate distinctions. In other words, students with increased deep time knowledge were better able to decouple recent weather phenomena from the scientific evidence supporting human-induced global climate change. Students with greater deep time knowledge may be able to conceptualize about the temporal aspect of the distinction, where weather covers time periods ranging from minutes to a few years and climate covers periods ranging from a few decades and longer.
Increased knowledge about deep time may facilitate students to more easily transition from their everyday perspective (e.g., observing weather events) to the scientific (e.g., inferring that climate is changing based on long-term data sets), a necessary condition for conceptual change (Duit, Treagust, & Widodo, 2008). Students who are able to transfer deep time knowledge into other domains (e.g., astronomy and geology) may also acquire robust diachronic thinking schemes, which positions them to gain a better understanding of evolutionary processes over very long time periods (Montagnero, 1996). Students have the ability to develop deep time knowledge, and through instructional intervention, we may be able to create a robust understanding of transformations over very long time periods and strengthen their knowledge of many important scientific phenomena of great importance to our society, such as global climate change.
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