Reversals of Earth's Magnetic Field During the Past 5 Million Years

Reversals of Earth's magnetic field during the last 5 million years

Image courtesy USGS.

This image shows the reversals of Earth's magnetic field over the past 5 million years. The scale along the left is time, going backward from the present as you move down the page, in millions of years before the present day. Chrons are long periods during which the magnetic field remained oriented in one direction for most of the duration of the chron. The current chron, called the "Brunhes normal", began 780,000 years ago. The immediate prior chron was the "Matuyama reverse". Periods during which Earth's magnetic polarity was "normal" (that is, the same as it is now) are shown in black, whereas periods of reversed polarity are shown in white. Most chrons are interrupted by shorter periods, called subchrons, during which the field flips to the opposite of the dominant orientation during the longer parent chron.

Last modified November 10, 2006 by Randy Russell.

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Magnetic Field

The force of magnetism causes material to point along the direction the magnetic force points. As shown in the diagram to the left, the force of magnetism is illustrated by lines, which represent the force....more

Content for Climate Change Education Courses

Looking for online content that can be used for a climate change education course or module? Pages linked below can be used to support an introductory climate change education for either a unit or a full...more

The Earth's Magnetic Field

The Earth has a magnetic field with north and south poles. The Earth's magnetic field reaches 36,000 miles into space. The magnetic field of the Earth is surrounded in a region called the magnetosphere....more

The Discovery of the Radiation Belts

The belts of trapped radiation above the Earth's atmosphere, but within the magnetosphere, were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts. When...more

Earth's Magnetic Poles

Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more

Earth's North Magnetic Pole

Earth has a magnetic field with a north pole and a south pole. Earth's magnetic field is pretty much (but not exactly) like the magnetic field around a bar magnet. Earth's North Magnetic Pole (NMP) is...more

Altocumulus

Altocumulus clouds are part of the Middle Cloud group (2000-7000m up). They are grayish-white with one part of the cloud darker than the other. Altocumulus clouds usually form in groups and are about...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA