Online Investigation of an Island Arc Volcano: Anatahan, Mariana Arc

Jeffrey G. Ryan, University of South Florida

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Current students have online access to nearly unlimited information in an entirely unfiltered state. As such, they need guidance in training in assessing information quality and identifying high-quality information resources for educational and research use. In this activity, students will conduct a directed Web surf/search effort for information on and datasets from the Anatahan arc volcano, which they will use in an interpretive study of recent magmatic activity in the Mariana arc. Students should have been exposed to concepts related to magma genesis and the nature of subduction zone magmatism before conducting this activity. As well, a rudimentary knowledge of trace element geochemistry and its application to the study of igneous rocks is expected, or should be prepared for if this activity is used.

The activity is designed as an extended homework "project" exercise that complements hands-on laboratory work in volcanic rock description and analysis. An intent of the activity is to help students connect the volcanic rock samples they see in the lab to a real volcanic event that they discover through their own research efforts.

Anatahan 2003 eruption

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Learning Goals

This activity provides hands-on experience with effective Web-based searching for scientific information, and with extracting valid and useful data from information resources. It will familiarize students with several useful Web resources related to petrology and geochemistry (i.e., the MARGINS website, the GERM site, and other related web resources on the Izu-Bonin-Mariana Focus Area.

The activity also has students making interpretive use of petrologic data on volcanic rock samples to understand the nature of magma sources and the impacts of crystallization processes on magma composition. Students do basic geochemical data analysis that directly models approaches used by field petrologic researchers.

Students will also gain useful experience in the research use of several common computer software packages (i.e., the Microsoft Office suite programs, +/- petrologic graphing program packages).

Context for Use

This Web investigative activity is designed for use in the later portions of a petrology or mineralogy/petrology course. As the student activities necessitate higher-order thinking, it is important that they have some background in the study of subduction zone processes and volcanic arcs, and in the study of magma processes and igneous rock formation, before undertaking this activity. Expanding the graphical element analysis parts of this activity beyond what is described is an effective way of engaging students in some of the basics of trace element geochemistry (i.e., elemental partitioning during igneous processes).

Description and Teaching Materials

Included is a handout that outlines the Anatahan acitivity in a step-by-step format. All other resources required can be accessed through the website references provided. Students will no doubt discover new resources that are not on the list below, which is a very good thing.

The handout for the Anatahan Web search/analysis activity (Microsoft Word 35kB Apr3 07)


Included for the benefit of the instructor is an Microsoft Excel workbook compiling Anatahan data from the 2006 Journal of Volcanology and Geothermal Research issue on the 2003 Anatahan eruption, which includes a few exemplar diagrams. 

Excel workbook for Anatahan sample data (Excel 162kB Apr5 07)

Teaching Notes and Tips

The normal student response will be to Google for information on the volcano. One can't stop this happening, so it is important to take the time to discuss what are and aren't scientifically valid resources.

It will also be important to have a significant discussion about what constitutes plagiarism of Web resources, given that this is an area where students seem to have extreme difficulties.

There are a subset of students (both older and younger) who are phobic of any non-toy computer software - these students will hit walls repeatedly trying to tabulate data and make plots in Excel. A brief visual description of reasonable ways to tabulate chemical data and a how-to on making simple graphs may be required.


Each student will generate a report including a specific set of tables and plots, responses to specific questions, and a list of Web and literature references used in their investigation. One can choose to assess this as a research activity, focusing on the breadth and quality of the information gathered; as an interpretive exercise, focusing on their thinking as to their compiled datasets and their graphical patterns; or as a problem set of sorts, seeking specific answers to the questions posed.

References and Resources

Front page for the 2003 Anatahan eruption resources in the NSF-MARGINS website.
The homepage of the Geochemical Earth Reference Model (GERM). This site maintains current compilation of rock compositional data and elemental partition coefficient information. 
This is the homepage for EarthChem, the largest online repository of bulk rock composition and trace element geochemical data for igneous rocks. 

Hanson, G.N., 1989: An Approach to Trace Element Modeling Using a Simple Igneous System as an Example. In Reviews of Mineralogy and Geochemistry, Volume 21: Mineralogy and Geochemistry of the Rare Earth Elements (B.R. Lipin & G.A. McKay, Editors) A good descriptive explanation of the use of element-element variation plots to examine melting and crystallization processes in volcanic rocks - useful background material for this activity. 

Selected papers from the 2005 Journal of Volcanology and Geothermal Research Special Issue on the Anatahan eruption: 

Wade, J.A., T. Plank, R. J. Stern, D. L. Tollstrup, J. B. Gill, J. C. O'Leary, J. M. Eiler, R. B. Moore, J. D. Woodhead, F. Trusdell, T. P. Fischer, D. R. Hilton, 2005: The May 2003 eruption of Anatahan volcano, Mariana Islands: Geochemical evolution of a silicic island-arc volcano. Journal of Volcanology and Geothermal Research, vol. 146, pp 139-170 

Pallister, J.S., F. A. Trusdell, I. K. Brownfield, D. F. Siems, J. R. Budahn, S. F. Sutley, 2005: The 2003 phreatomagmatic eruptions of Anatahan volcano-textural and petrologic features of deposits at an emergent island volcano. Journal of Volcanology and Geothermal Research, vol. 146, pp 139-170