This is a partially developed activity description. It is included in the collection because it contains ideas useful for teaching even though it is incomplete.

Initial Publication Date: February 12, 2008

Lithospheric flexure in Hawaii

Andrew Goodwillie, Kim Kastens, Linda Sohl, Jaime Toro, Amy Cline, Shelley Olds, Rob Graziono, Sarah Titus, Erin Heffron, Chuck Anderson, Jim Washburn, Steve Reynolds, Ron Schott, and Charlie Onasch
Topic: Tectonics
Course Type: upper level

Description

Students use GeoMapApp to investigate lithospheric flexure in the Hawaiian islands. Students make 2D profiles of bathymetry and gravity data across the big island of Hawaii and the adjacent seafloor. They can also look at seismic profiles from the region to estimate sediment thickness. These data can then be used as input into a calculation of lithospheric flexure which requires (1) the deflection of lithosphere (from bathymetry and sediment thickness) and (2) the distance from the center of the load (Hawaii) to the crest of the forebulge (bathymetry) in order to calculate the flexural rigidity using an Excel spreadsheet. The size of the load can be changed in the spreadsheet until it matches the true gravity profile. The geodynamical equations for this calculation can be found in Turcotte and Schubert.

Some variations might include:
-looking at gravity data alone (at first) and make a mental model for explaining the gravity high centered on Hawaii and the gravity low around the island (before discussing lithospheric flexure)
-looking at gravity/bathymetry/seismic data from somewhere further up the Hawaiian-Emporer seamount chain to see the decay of lithospheric flexure (as time slices)

Goals

-interpretation of gravity data
-intuitive understanding of lithospheric flexure
-experience using GeoMapApp (which may come in handy in other classroom contexts)