Extent of available data.
This data layer depicts the variation in the Earth's magnetic field resulting from the magnetic properties of the underlying geology. It was developed by the Minnesota Geological Survey (OFR-07-06). The variations in the aeromagnetic values are related to anomalous magnetic properties of rock units within the Earth. In general, it reflects the variable distribution of the mineral magnetite (Fe3O4). Magnetic data is a key basis for geological mapping, and it helps geologists and geophysicists understand the internal structure of Earth in general, and the bedrock geology of Minnesota in detail.