Magnetic stripes on credit cards hold important data.
There are two different types of magnetic striping. One is a phenomenon that appears on the ocean floor; the other is a method of encrypting data on plastic cards.
Ocean Floor Phenomenon
The earth’s magnetic field has reversed several times over the past few million years, and magnetic north became magnetic south. One way scientists chart reversals is through the magnetic striping on volcanic rocks on the ocean’s floor. When a volcano erupts, the lava forms some rocks that are slightly magnetized. The rocks follow earth’s prevailing magnetic field. During periods of magnetic reversal, the magnetization of volcanic rock also reverses. That creates magnetic striping.
Plastic cards and documents used for identification and account verification have a magnetic stripe on the back. The stripe is encrypted with data the issuer considers essential, like name and account number. While not absolutely secure, recent improvements in magnetic striping encryption make it exceedingly difficult to access the encrypted information illegally.
Magnetic Stripe Readers
Magnetic stripe card readers are everywhere.
Card readers are at most locations that accept credit cards. If the magnetic stripe becomes demagnetized, it can no longer be read and is useless for automated tasks.