Geophysics is a way of studying the geology and structure of the Earth by measuring its physical properties.

Geophysics involves:

  • The collection of data (such as measurements of the Earth’s magnetism or gravity) using geophysical surveys
  • The processing of geophysical data to create maps and images
  • The interpretation of the data to better understand the geology below the surface

Ontario Geological Survey

The role of the Ontario Geological Survey in geophysics is to:

  • Acquire new geophysical data in Ontario
  • Publish the geophysics as maps and digital data
  • Use geophysics to assist with the geological mapping of Ontario


Geophysics is used to help “see” rocks and minerals that are hidden below the surface. Much of Ontario is covered by a thick blanket of overburden that was deposited by glaciers as they retreated at the end of the last Ice Age. In many areas, because there is little rock exposed at surface, geologists and mineral prospectors must use geophysics to help them with their work.

In addition to measuring the Earth’s magnetic and gravitational properties, geophysics is used to measure electrical properties, naturally occurring radioactivity and acoustic (seismic) properties. Many of these surveys can be performed from the air and/or on the ground and even underground in boreholes and mines.

As well as being used for geological mapping and mineral exploration, geophysics can be used for land-use planning, engineering studies, mapping underground water resources and for energy exploration.

When performed from the air, using specially modified aircraft, geophysical surveys can quickly cover very large and remote areas such as the northern areas of the province. Without the need to go on the land, airborne geophysical surveys have very little impact on the environment.

Ontario Geological Survey Geophysical Data

View the Geophysical Survey index in GoogleEarth kml format.  The Geophysical index contains boundaries illustrating areas that have published digital data products released by the Ontario Geological Survey.
Data includes: locations of published airborne surveys, regional magnetic and gravity surveys, seismic and magnetotelluric data with links to download the data from GeologyOntario.
Download the Geophysical Survey Index in ESRI shape file format.