This is a map of the earth's gravity field, produced by the GRACE satellite (Gravity Recovery and Climate Experiment) project. These are twin satellites, making detailed measurements of Earth's gravity field which will "lead to discoveries about gravity and Earth's natural systems". (The CU Geophysics group is involved with this project.) The image above shows the "gravity anomaly", a measure of the difference between what "g" is, and what it would be for a simple "model" earth (squashed at the poles and elongated at the equator due to motion) It shows you information about the mass distribution of the underlying earth. (Can you generate any ideas of why, e.g. the Andes have such anomalous positive gravity above them? Or, why Canada's Hudson's bay region appears to have a negative anomaly?)
I welcome your comments on the class and this website.
Send them to steven.pollock at colorado.edu