Understanding and Applying the Exner Equation

Chris Paola

Department of Geology & Geophysics/University of Minnesota

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Initial Publication Date: July 14, 2006 | Reviewed: June 24, 2014 (see revision history: 2 events)

Summary

The Exner equation lends itself readily to visualization and physical examples; it is far more important in quantitative sedimentary geology than the usual topics from fluid mechanics that are included in undergraduate sedimentary geology texts. We will look 'under the hood' of the Exner equation and discuss what its terms mean and how to present it to undergraduates with emphasis on building intuition rather than mathematical solution methods.

Sediment Transport and Deposition | College Lower (13-14), College Upper (15-16)

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Context

Audience

undergraduate required course in sedimentary geology

Skills and concepts that students must have mastered

differential calculus

How the activity is situated in the course

topic presented early in the course, just after sediment properties

Goals

Content/concepts goals for this activity

physical sedimentation

Higher order thinking skills goals for this activity

ability to understand physical meaning of terms in a simple but crucial differential equation; relation of mathematics to nature; estimation and simplification

Other skills goals for this activity

Description of the activity/assignment

The Exner equation describes the mass balance for sediment deposition and erosion. The original version embodies the main short-term processes of deposition and creation of the stratigraphic record is created. It can easily be modified to include additional processes like subsidence, compaction, and carbonate or evaporite formation. The Exner equation is far more important in quantitative sedimentary geology than the usual topics from fluid mechanics that are included in undergraduate sedimentary geology texts.

The goal is to take the equation apart to help undergraduates develop a physical intuition for what they mean and how they can be estimated using simple measures like length and time scales. The emphasis is on building intuition rather than mathematical solution methods.