On the Cutting Edge - Professional Development for Geoscience Faculty
Teaching Structural Geology, Geophysics, and Tectonics in the 21st Century
University of Tennessee, Knoxville
Cutting Edge > Structural Geology > Structure, Geophysics, and Tectonics 2012 > Teaching Activities > Measuring the vertical gradient of gravity

Measuring the vertical gradient of gravity

Rob Sternberg, Franklin & Marshall College

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Summary

The free-air effect tells us that as elevation above sea level increases, gravitational acceleration g decreases at the rate of about 0.3086 mgal/meter. This effect is routinely corrected for when making gravity surveys. We will use the LaCoste & Romberg gravimeter to measure the free-air effect in a tall building on campus, and compare with the theoretical value.

keywords: gravity; vertical gradient; gravimeter

Context

Audience

undergraduate elective course in geophysics

Skills and concepts that students must have mastered

follow instructions to use an expensive and delicate instrument
use a spreadsheet to tabulate, graph and analyze numerical data

How the activity is situated in the course

As a two-week lab exercise, one week for measurement in small groups, and one week for analysis

Goals

Content/concepts goals for this activity

effects on gravitational acceleration

Higher order thinking skills goals for this activity

analysis of data acquired
formulation of hypotheses why experimental value may not agree with accepted value
consideration of accuracy, precision, and replicability of results

Other skills goals for this activity

writing of lab report in scientific paper format
operating analytical equipment
working in groups to collect data and interpret results

Description and Teaching Materials

Vertical gradient of gravity lab handout (Microsoft Word 2007 (.docx) 19kB Apr30 12)

Teaching Notes and Tips

Needs a gravimeter
Data must be reviewed by instructor and errors parsed, especially if data are to be shared among groups

Assessment

Writeup of lab report in scientific paper format

References and Resources

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