Increase in volcanism at the beginning of the Holocene on Reykjanes, Iceland: case example

Barbara Tewksbury, Hamilton College

Author Profile


Students make simple stress calculations to determine whether deglaciation at the end of the Pleistocene may have been responsible for a short but dramatic increase in rates of volcanism on Reykjanes in Iceland as a result of depressurization of the underlying mantle.

Used this activity? Share your experiences and modifications



Structural geology course for geo majors.

Skills and concepts that students must have mastered

General stress principles, lithostatic stress, general knowledge about plate tectonics, igneous rocks, volcanism.

How the activity is situated in the course

In some years, I have used this as part of a homework assignment and, in other years, as part of a take-home exam. It could also be used s an in-class activity.


Content/concepts goals for this activity

The primary goal is for students to apply content and concepts that they have already learned, but they also learn about generation of magmas by decompression melting, the early Holocene volcanic and deglaciation history of Iceland, and the usefulness of structural geology concepts in another discipline.

Higher order thinking skills goals for this activity

Calculate an estimate for the amount of magma produced by depressurization and evaluate a hypothesis based on their calculations and plus additional data.

Other skills goals for this activity

Description and Teaching Materials

Students begin by calculating an approximate per cent increase in mantle melting that could be produced by melting a 2 km thick ice sheet on Reykjanes. They then extrapolate to a melt volume using a ballpark estimate for the volume of mantle involved in partial melting beneath Reykjanes. They also need to make calculations that allow them to relate the rates of volcanism in the data that they are given to the volumes that they have calculated. Students then evaluate the hypothesis that deglaciation was responsible for the difference in rate of volcanism in the Early Holocene in comparison to the rest of the Holocene. They then address the question of why the volume of magma that they calculated does not match the volume erupted in the Early Holocene.

Assignment for Reykjanes volcanism case example (Microsoft Word 2007 (.docx) 347kB May10 12)

Teaching Notes and Tips


Students individually submit written analyses with argument and evidence.

References and Resources

Jull, M. and McKenzie, D., 1996, The effect of deglaciation on mantle melting beneath Iceland: JGR, v. 101, no. B10, p. 21,815-21,828.