An Instructor's guide to Rates in Geology

by Dr. Eric M. Baer, Geology Program, Highline Community College and Dr. Jennifer M. Wenner, Geology Department, University of Wisconsin Oshkosh
Road sign with metric/english

What should the student get out of this page?

When the student finishes this module he or she should be able to:
  1. Calculate a rate given 2 values and the times they were measured
  2. Recognize a wide variety of rates examined in the geosciences
  3. Determine a rate from a graph in which time is on the x axis

Why is it hard for students?

Rates are often difficult for students because they have not had exposure to rates other than velocities. Rates beyond simple velocity are not taught until calculus. As a result, even though many geoscientists and teachers view it as basic, many students may not have been taught how to calculate rates in a systematic way.

What don't we include in the page?

We do not discuss derivatives, even though derivatives are the rate of change since we find very few instructors using this in introductory geoscience courses. This page only deals with constant rates of change because variable rates require calculus, which is often beyond the skill set of students in introductory courses.

When developing this page, we avoided using the better known equation R=d/t where d is distance. Instead, we use ΔX because this is a much more general equation - applicable where ΔX is distance but also applicable when it is something like temperature change. However, for a student that is really struggling it might be helpful to start with the specific well known example and then introduce the general equation.

Instructor resources

Rates, Dates and Geologic Time: Teaching about the Temporal Aspects of Geoscience contains a variety of teaching activities and visualizations.

There are numerous teaching activities for looking at specific rates in the SERC teach the Earth collection especially relevant ones may be found in the Starting Point Collectionwhich focuses on teaching introductory geoscience classes.

Bailey, C.M. (2000) Rates of Geologic Processes: Problems for an Introductory Geology Course. Mathematical Geology, Volume 32, Number 2, February 2000, pp. 151-158.

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