In geophysics

Geophysics

Geophysics is the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods. The term geophysics sometimes refers only to the geological applications: Earth's shape; its gravitational and magnetic fields; its internal structure and...

, a magnetic anomaly is a local variation in the Earth's magnetic field

Earth's magnetic field

Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...

 resulting from variations in the chemistry or magnetism of the rocks. Mapping of variation over an area is valuable in detecting structures obscured by overlying material. The magnetic variation in successive bands of ocean floor parallel with mid-ocean ridge

Mid-ocean ridge

A mid-ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges , typically having a valley known as a rift running along its spine, formed by plate tectonics. This type of oceanic ridge is characteristic of what is known as an oceanic spreading...

s is important evidence supporting the theory of seafloor spreading

Seafloor spreading

Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics....

, central to plate tectonics

Plate tectonics

Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

. These layers are used for dating rocks.

See also

• Aeromagnetic survey
  Aeromagnetic survey
  An aeromagnetic survey is a common type of geophysical survey carried out using a magnetometer aboard or towed behind an aircraft. The principle is similar to a magnetic survey carried out with a hand-held magnetometer, but allows much larger areas of the Earth's surface to be covered quickly for...
  
  
• Earth's magnetic field
  Earth's magnetic field
  Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...
  
  
• Kursk Magnetic Anomaly
  Kursk Magnetic Anomaly
  Kursk Magnetic Anomaly is a territory rich in iron ores located within the Kursk, Belgorod, and Voronezh oblasts in Russia, and constitutes a significant part of the Central Chernozyom Region...
  
  
• Magnetometer
  Magnetometer
  A magnetometer is a measuring instrument used to measure the strength or direction of a magnetic field either produced in the laboratory or existing in nature...
  
  
• Temagami Magnetic Anomaly
  Temagami Magnetic Anomaly
  The Temagami Magnetic Anomaly, also called the Temagami Anomaly or the Wanapitei Anomaly, is a large buried geologic structure in Ontario, Canada, stretching from Lake Wanapitei in the west to Bear Island in Lake Temagami....