Parícutin magnetic survey
Ralph R. Bodle · Transactions American Geophysical Union · 1944
This survey was a joint project of the United States Department of State and the United States Coast and Geodetic Survey. The purpose was to learn whether any detectable change had occurred in the Earth's magnetic field in the region as a result of the volcano. Work started the latter part of May and continued well into July, 1943. The Mexican Government cooperated enthusiastically, giving assistance in every possible way.