Teach the Earth > GIS and Remote Sensing > Activities > Exercise 7: Plate Boundaries in the Woodlark Basin Region

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# Exercise 7: Plate Boundaries in the Woodlark Basin Region

Barbara and David Tewksbury, Hamilton College

### Summary

Students use a variety of data sets (bathy DEMs, SRTM DEMS, earthquake data, volcano data, ocean floor ages, and motion vectors) to 1) determine the locations and types of plate boundaries in the complex region between the Pacific and Australian Plates, 2) create a topologically valid plate map of the region (which identical to making a geologic map in ArcMap, so it teaches them how to make a geologic map as well), 3) make a poster presentation with a cartographically complete map and illustrated rationale for plate boundaries, and 4) do an extension on plotting strike and dip data in ArcMap. You might also be interested in our Full GIS course with links to all assignments.

## Context

Type and level of course
Entry level GIS course for geoscience students.

Geoscience background assumed in this assignment
Knowledge of the characteristic features of plate boundaries, basic understanding of plate motion vectors and ocean floor relative ages.

GIS/remote sensing skills/background assumed in this assignment
Projections and coordinate systems, symbolizing and colorizing layers, hillshading, layer manipulation, ArcScene basics, working with rasters and shapefiles.

Software required for this assignment/activity:
ArcGIS (ArcInfo license level) with Spatial Analyst extension and ArcScene.

Time required for students to complete the assignment:
A week and half of class plus homework.

## Goals

GIS/remote sensing techniques students learn in this assignment
Hillshading an unprojected raster using a Z factor; clipping a raster and a shapefile specific lat/lon coordinates; adding X-Y data to ArcMap from an Excel spreadsheet; customizing color ramp symbology; portraying a 3D point data set in ArcScene for visualization; georeferencing; editing a shapefile, adding lines with attributes, symbolizing by attributes, and using geological symbols; understanding edges, vertices, and ends; snapping and snapping tolerances; working with values in symbology; editing common boundaries in a polygon shapefile using the topology edit tool; creating a geodatabase; adding feature datasets and feature classes; creating and using domains; performing a topological analysis; converting lines to polygons to create a topologically valid geologic map.

Other content/concepts goals for this activity

Higher order thinking skills goals for this activity
Combining multiple data sets for analysis of a problem without a unique solution.

## Description of the activity/assignment

This is Exercise 7 in a semester-long GIS for Geoscientists course. You can find the other exercises in this series on the course summary page or by typing Tewksbury GIS Exercise into the Cutting Edge search engine.

The region between the Pacific and Australian Plates in the southwest Pacific is tectonically complex, with many microplates and plate boundaries. The Woodlark Basin region, lying south of the Solomon Islands and north of the Coral Sea, is particularly interesting. NASA's quite excellent world plate map (http://___) shows the Woodlark Basin but does not provide any plate boundary detail for the Basin.

In this four-part exercise, students evaluate the nature and locations of plate boundaries in this area based on multiple data sets (bathy DEMs, SRTM DEMS, earthquake data, volcano data, ocean floor ages, and motion vectors) and defend the analysis. This exercise also introduces students to making a geologic map in ArcMap using a geodatabase and performing a topological analysis.

Although students could do library research to find a variety of published plate maps for this region, their assignment is to do the analysis based solely on the data sets allowed for this assignment. Each student turns in a signed page certifying that they have not consulted other data or sources.

Exercise 7b: In this lab exercise, students create a base map for the region that shows topography, bathymetry, volcanism, seismicity, seafloor ages, and plate motion vectors. Making the basemap involves adding X-Y data (earthquakes and volcanoes), clipping the various data sets to the same geographic area, creating a hillshade using a Z factor, and georeferencing the two jpegs. Students also create a 3D view of regional earthquakes in ArcScene, calculating the Z factor to accurately portray earthquake depths.

Exercise 7c: In this homework, each student uses the multiple data sets in the ArcMap from Exercise 7b to analyze the locations and types of plate boundaries in the area and to create an initial plate boundary map in ArcMap. They make their plate boundary maps by creating and editing a shapefile with a field for plate boundary type. They work with snapping and snapping tolerance, line editing, and symbolizing.

Exercise 7d: In this lab exercise, students explore the limitations of creating and editing a geologic map using shapefiles. To overcome the limitations, students develop a geodatabase for creating a plate map of the region, showing each plate in a different color and the various types of plate boundaries with different symbols. The exercise involves creating domains and a topology for the geodatabase, drawing the plate boundaries in the feature dataset, testing for violations of the topology rules, fixing topological violations, generating polygons from the line feature classes, and adding a field with plate names to the polygon feature class. The final product is a formal poster that has a complete ArcMap plus additional text boxes and graphics that outline the evidence for the locations and types of plate boundaries.

Exercise 7e: The plate map that students develop for the Woodlark Basin region is like a standard geologic map in all respects except for the addition of strike and dip data. The last part of this exercise is designed to give them practice in using ArcGIS Help to figure out how to plot a set of strike and dip data and symbolize them correctly in ArcMap.

## Determining whether students have met the goals

Students are assessed on the following: 7b – quality of basemap showing bathymetry, topography, volcanoes, and earthquakes and quality of ArcScene jpeg that shows the earthquakes in 3D; 7c - reasoning behind their initial plate boundary maps; 7d - quality of the final ArcMap, and on the accuracy and quality of the arguments and evidence for the locations and type of plate boundaries on their final posters.

## URLs and References

Students download virtually all of the data for this activity from the Internet, and the URLs are listed in the assignments themselves. Two other data sets have been provided by colleagues and can be downloaded below. Andy Goodliffe (University of Alabama) has provided a high resolution data set for the central part of the Woodlark Basin. Suzanne Baldwin (Syracuse University) has provided data on ocean floor ages and plate motion vectors, and students georeference the jpegs containing these data.