Teach the Earth > Rates and Time > Workshop 2012 > Participants and their Contributions > Cara Thompson

Teaching vastness of Earth's history and past vs present climate/oceanographic changes

Cara K. Thompson, Department of Geosciences, Stony Brook University


­I have taught a historical geology class in a region of the US that is referred to as the "bible belt" in which students fly through all of Earth's history within a few short months. For this reason, it is understandable to me that, given their background, students lack a good understanding of and are, therefore, skeptical of concepts like evolution and plate tectonics. I find that it is difficult to convey a sense of the time scales on which geologic processes occur. My goal is not to challenge their beliefs, but rather give them tools to understand geologic processes and to think about geology in a more scientific matter. One of the exercises I have students do is pick something that they are familiar with (the example that is commonly used is a football field), and have them calculate how much of that object represents different intervals of geologic time. In the football field analogy, if the formation of Earth occurs at the zero yard line, one of the important milestones in Earth's history, the advent of biomineralization (beginning of the Cambrian time period; ca. 542 Ma), doesn't occur until the 88th yard line. The entire existence of Homo sapiens on Earth spans the last two mm of the football field. I think this exercise gives them a visualization of the vastness of geologic time and can be used throughout the course.

Additionally, I have taught a class about global climate change in the context of climate change throughout the Earth's past. In this class, students are typically very driven to understand modern climate change and have more difficulty grasping climate change on longer time scales. Since there is so much misinformation, I feel it is important to address how the ocean-atmosphere-geosphere system responds to increased atmospheric carbon dioxide and what those responses mean for the global society. The goal is to have them understand which natural processes and potential remedial strategies will work on a human time scale and which require much longer time scales.

My research focuses understanding what drives changes in Paleozoic marine environments. I constructed a sulfur isotope curve for the Ordovician, which showed short-term changes superimposed over a longer-term trend. High-resolution geochronologic analyses of zircons from bentonite beds that were interlayered with the marine deposits suggest small-scale change occur at a scale of 105 years. Determining time scale of variation is important because it can be used to calculate marine sulfate reservoir size and concentration for the Ordovician as well as narrow down the list of potential drivers of sulfur isotope variation.

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