Reversals of Earth's Magnetic Field During the Past 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.
Shop Windows to the Universe Science Store!
Our online store
includes issues of NESTA's quarterly journal, The Earth Scientist
, full of classroom activities on different topics in Earth and space science, as well as books
on science education!
You might also be interested in:
The force of magnetism causes material to point along the direction the magnetic force points. This property implies that the force of magnetism has a direction. As shown in the diagram to the left, the...more
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 has a magnetic field with north and south poles. The magnetic field of the Earth is enclosed in a region surrounding the Earth called the magnetosphere. As the Earth rotates, its hot core generates...more
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 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 has a global magnetic field that is approximately, though not exactly, a dipole field (like a bar magnet) with a north pole and a south pole. Earth's North Magnetic Pole (NMP) is not in the same...more
Altocumulus clouds (weather symbol - Ac), are made primarily of liquid water and have a thickness of 1 km. They are part of the Middle Cloud group (2000-7000m up). They are grayish-white with one part...more