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Magnetic Seafloor Anomalies

Global map of magnetic anomalies imprinted onto the seafloor of the Earth in form of characteristic stripes and other patterns.


Global map of magnetic anomalies imprinted onto the seafloor of the Earth in form of characteristic magnetic stripes and other patterns. The magnetic anomalies are not only observable on the seafloor, but also provide insight into the subsurface structure and composition of the Earth’s crust. Anomalies trending parallel to the isochrons (lines of equal plate age) in the oceans reveal the temporal growth of oceanic plate and crust: seafloor spreading.

Ever so often the Earth’s magnetic field flips its polarity in an occurrence called a geomagnetic reversal. These reversals throughout Earth’s history are recorded in solidifying rocks, such as in the ones making up the growing oceanic crust at mid-oceanic ridges. The successive bands of ocean floor representing alternating magnetic polarity parallel with mid-ocean ridges was important evidence for seafloor spreading, the concept central to the acceptance of the early theory of plate tectonics.

The data plotted is from the global Earth Magnetic Anomaly Grid (EMAG2) and was compiled from satellite, ship and airborne magnetic measurements.

  • Various other map projections included
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  • Readable in black&white

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Earth’s magnetic field (collection)

A graphics collection representing multiple interesting aspects related to the Earth’s magnetic field.

A graphics collection representing multiple interesting aspects related to the Earth’s magnetic field. These include the following: 1) Rocks can capture the Earth’s magnetic field when they are formed; 2) The Earth’s magnetic field protects us from solar storms; 3) The magnetic and geographic poles of the Earth are not currently in the same location; 4) The magnetic poles of the Earth have switched position many times in the past; 5) The frequency of reversals is highly variable; 6) Reversals are not linked to biologic extinction events; 7) The Earth’s magnetic field of the past can be used to reconstruct plate tectonics.

  • Creator: Annique van der Boon
  • This version: 03.05.2023
  • License: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
  • Specific citation: These graphics by Annique van der Boon from van der Boon (2019) are available via the open-access s-Ink.org repository.
  • Related reference: A. van der Boon (2019), 10 things you might not know about Earth’s magnetic field, DOI: 10.13140/RG.2.2.17119.82089
  • Individual-element versions
  • Vector-format versions
  • Transparent-background versions
  • Colour-vision deficiency friendly
  • Readable in black&white

Faulty or missing link? – Please report them via a reply below!

Earth’s magnetic field (overview)

Schematics outlining key elements of the Earth’s magnetic field that is produced in the hot, liquid Outer Core, varies in strength, and even reverses multiple times through the planet’s evolution.

Schematics outlining key elements of the Earth’s magnetic field that is produced in the hot, liquid Outer Core, varies in strength, and even reverses multiple times through the planet’s evolution.

  • Creator: Annique van der Boon
  • This version: 02.05.2023
  • License: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
  • Specific citation: These graphics by Annique van der Boon from van der Boon (2019) are available via the open-access s-Ink.org repository.
  • Related reference: A. van der Boon (2019), 10 things you might not know about Earth’s magnetic field, DOI: 10.13140/RG.2.2.17119.82089
  • Individual-element versions
  • Vector-format versions
  • Transparent-background versions
  • Colour-vision deficiency friendly
  • Readable in black&white

Faulty or missing link? – Please report them via a reply below!

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