Is the Earth a magnet?

In a sense, yes. The Earth is composed of layers having different chemical compositions and different physical properties. The crust of the Earth has some permanent magnetization, and the Earth’s core generates its own magnetic field, sustaining the main part of the field we measure at the surface. So we could say that the Earth is, therefore, a "magnet."

But permanent magnetization cannot occur at temperatures above about 650 degrees Celsius (1,200 degrees Fahrenheit), when the thermal motion of atoms becomes too vigorous to maintain the ordered orientations needed for permanent magnetization. The core of the Earth has a temperature of several thousand degrees Celsius, and is not permanently magnetized.

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What do the different north arrows on a USGS map mean?

At the bottom of most USGS topographic quadrangle maps is a diagram that shows three north arrows -- true north, grid north, and magnetic north -- and the angles between them. Some maps, especially very old maps, do not have this diagram. True north, also called geodetic north or geographic north, is the direction of the line of longitude that...

Why measure the magnetic field at the Earth's surface? Wouldn't satellites be better suited for space-weather studies?

Satellites and ground-based magnetometers are important for making measurements of the Earth’s magnetic field. They are not redundant but are instead complementary. Satellites provide good geographical coverage for data collection. Ground-based magnetometers are much less expensive and much easier to install than satellites. An array of...

Does the Earth's magnetic field affect human health?

Not directly. High-altitude pilots and astronauts can experience higher levels of radiation during magnetic storms, but the hazard is due to the radiation, not the magnetic field itself. Direct effects on human health from the magnetic field at the Earth's surface are insignificant. Geomagnetism can impact the electrically-based technology that we...

What is declination?

At most places on the Earth's surface, the compass doesn't point exactly toward geographic north. The deviation of the compass from true north is an angle called "declination" (or "magnetic declination"). It is a quantity that has been a nuisance to navigators for centuries, especially since it varies with both geographic location and time . It...

Are we about to have a magnetic reversal?

Almost certainly not. Since the invention of the magnetometer in the 1830s, the average intensity of the magnetic field at the Earth's surface has decreased by about ten percent. We know from paleomagnetic records that the intensity of the magnetic field decreases by as much as ninety percent at the Earth's surface during a reversal. But those...

How does the Earth's core generate a magnetic field?

The Earth's outer core is in a state of turbulent convection as the result of radioactive heating and chemical differentiation. This sets up a process that is a bit like a naturally occurring electrical generator, where the convective kinetic energy is converted to electrical and magnetic energy. Basically, the motion of the electrically...

Do animals use the magnetic field for orientation?

Yes. There is evidence that some animals, like sea turtles and salmon, have the ability to sense the Earth's magnetic field (although probably not consciously) and to use this sense for navigation.

Could magnetic reversals be caused by meteorite or comet impacts?

Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. But self-contained dynamic systems like Earth’s dynamo can do this without any outside influence. Reversals...

Is it true that Earth's magnetic field occasionally reverses its polarity?

Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature of the ambient magnetic field at the time of deposition. Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the...
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Date published: March 8, 2018

New 3D Measurements Improve Understanding of Geomagnetic Storm Hazards

Measurements of the three-dimensional structure of the earth, as opposed to the one-dimensional models typically used, can help scientists more accurately determine which areas of the United States are most vulnerable to blackouts during hazardous geomagnetic storms.

Date published: September 12, 2016

Mapping a Space-Weather Menace to Electric-Power Grids

New strides have been made toward quantifying how geomagnetic storms can interfere with the nation’s electric-power grid systems.  

Date published: December 18, 2013

A Modern Compass Improves Oil Production

By using the Earth's magnetic field, combined with new innovative technology, oil and gas drilling companies are increasing oilfield productivity while reducing development costs and environmental impacts.

Date published: May 23, 2006

USGS, NOAA Mark 50 Years of Geomagnetic Research at Corbin, Va.

 

On May 23, 1956, a research center and observatory opened at Corbin, Va. to continuously monitor the Earth's magnetic field. It was charged by Congress "to enhance geomagnetic field studies and monitoring programs in support of scientific, general public, basic and national security needs of the United States."

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Image: Fredericksburg Geomagnetic Observatory
June 30, 2011

Fredericksburg Geomagnetic Observatory

Main and auxiliary absolutes piers with Zeiss-Jena 010B Theodolites.

Image: Deadhorse Geomagnetic Observatory
August 1, 2010

Deadhorse Geomagnetic Observatory

Absolutes pier at Deadhorse geomagnetic observatory.

Image: Boulder Geomagnetic Observatory
August 31, 2009

Boulder Geomagnetic Observatory

Jeff Fox using a theodolite at the Boulder geomagnetic observatory.

USGS
October 16, 2007

Earth Science Week, Continued: Geomagnetism and the Self-Sustaining Dynamo Called Earth

USGS scientist Duane Champion explains the Earth's geomagnetic qualities and the potential for and possible consequences of a geomagnetic shift.

July 29, 2004

PubTalk 7/2004 — Secrets in Stone

The Role of Paleomagnetism in the Evolution of Plate Tectonic Theory Video Presentation

Presentation of the award-winning USGS video "Secrets in Stone" (35 minutes), introduced by Jack Hillhouse, Research Geophysicist, and followed by a tour of the USGS Paleomagnetics Laboratory

  • Crucial discoveries in the early 1960.s were made
...
Chart showing the Earth’s magnetic feild

Chart showing the Earth’s magnetic feild

This is one of five world charts showing the declination, inclination, horizontal intensity, vertical component, and total intensity of the Earth’s magnetic field at mean sea level at the beginning of 2005. The charts are based on the International Geomagnetic Reference Field (IGRF) main model for 2005 and secular change model for 2005-2010. The IGRF is referenced to the

...
Earths and its surroundings

EARTH

Earth and satellites

Image shows a diagram of a cross-section of the Earth

Earth Cross-Section

A cross-section of the Earth, showing the sub-surface layers that are being mapped.