The Magnetic Anomaly Map of Canada shows the variation of the magnetic field across the country. Magnetic anomalies reflect differences in the magnetic properties of the underlying bedrock, and the magnetic field is measured by a magnetometer. To collect aeromagnetic data, a magnetometer is installed in a small aircraft or helicopter and flown back and forth in parallel lines across a survey area perpendicular to the general strike of the bedrock.
The Geological Survey of Canada has been acquiring aeromagnetic data since 1947, and it has carried out more than 550 surveys. These surveys have allowed rapid geological assessment of vast areas. Indeed, the dominant structural trends of geological provinces can be recognized on the map.
The national dataset that supports this map has aided Survey geologists in understanding bedrock structure and composition beneath soil, vegetation, water, and ice. Available to the public, the data support mineral and hydrocarbon exploration programs, as well as land-use decisions.