James Trexler

University of Nevada, Reno

Introductory level geology

Beginning map reading, map scales, the concept of contouring data, interpolation, mathematical averages.

The lab project is used in the latter half of a unit on volcanoes.

Goals include calculation of tectonic plate motion rates from isotopic age data, and volcanic ash distribution from large hot-spot eruptions.

Both parts of this lab require students to assess data that is recorded as a range of values. Students must decide whether arithmetic averages give reasonable answers. The contouring part of the exercise involves interpolation.

This lab project is in two parts. In the first part students are given a map of Snake River Plain volcanic centers with a range of dates of eruptions. Based on what they know about hot-spot tracks, they use the map and reported isotopic ages to calculate a range of values for the relative velocities of the North American Plate and the Yellowstone hot spot. In the second part, students are given a map of the distribution of a volcanic ash from the Yellowstone volcanic field, with thickness of the ash where known. Students are asked to contour the map to show how the ash is distributed, and think about the factors that affect that thickness, both during and after the eruption. In both parts of the lab students have to deal with real data that is incomplete in some cases, and usually occurs as a range of values. Students must make decisions about how to treat incomplete data sets that do not have absolute values.

Written reports are graded based on completeness, and whether calculated values fall within reasonable limits (key included in file below). Classroom discussion during the exercise helps students get more comfortable with incomplete data sets.