Earth's Magnetic Field

“A moving ocean of liquid iron creates a magnetic bubble far larger than Earth.”

01 / PLAINLY

What it means, plainly

Earth's magnetic field arises mainly from conducting liquid iron moving in the outer core, a process called the geodynamo.

02 / CONTEXT

A little more

Convection, rotation, and electrical currents in the outer core maintain a changing field that extends as the magnetosphere. Magnetic poles drift, and polarity has reversed many times; rocks preserve part of this history.

03 / WHY IT MATTERS

Why it matters

It guides compasses, records plate motion, and deflects much of the solar wind, although it is not a perfect shield against all radiation.

04 / EXAMPLE

A familiar example

Alternating magnetic polarity frozen into basalt on both sides of ocean ridges helped confirm seafloor spreading.

05 / LIMIT

What it does not mean

A reversal does not switch the field off and on in one day, and evidence does not show that it automatically causes mass extinctions.

06 / NOTICE

Notice it in your day

Compare geographic north, magnetic north, and a compass direction in your area. Note why they need not line up exactly.

FINAL NOTE

The idea worth keeping

Separate the internal field, magnetosphere, and their changes across days to millions of years.

QUESTIONS / 02

Questions people still have

What mainly generates Earth's magnetic field?

Conducting iron moving in the outer core produces currents that sustain the geodynamo.

Do the magnetic poles remain fixed?

No. They continually drift, and global polarity has reversed irregularly many times.