How Do Cooled Lava Rocks Keep a Record of the Old Field?

What Crafty Clover says in this video

Intro

Hi there, curious minds! I'm Crafty Clover! Let's discover something amazing. How do cooled lava rocks keep a record of the old field?

The Big Idea

Rocks can remember! When lava cools, tiny magnetic grains in it line up with Earth's field at that moment. Let's see how rocks keep a record of the old field.

Lava Cools

Step one: lava cools. When lava cools, magnetic grains such as magnetite line up with Earth's field at that moment. The same thing can happen when tiny mineral grains settle in mud.

Locked in Place

Step two: locked in place. Once the rock hardens, the little grains are locked in place like frozen compasses. They keep pointing the way the field pointed long ago.

Reading the Record

Step three: reading the record. Scientists read this record to learn where the poles were and how the field has changed. Rocks like these are called a fossil compass.

A Closer Look

Let's take a closer look! Lava is hot and runny. Magnetic grains line up with the field. The rock hardens and locks them in. Scientists read that record later.

Quick Facts

Quick facts! These rocks are nicknamed fossil compasses. The grains point like frozen compasses. Scientists use them to find out where the poles were. They can read millions of years of history.

Think Like a Scientist

Now, think like a scientist! Draw a stack of rock layers. Add a tiny arrow in each layer showing which way the field pointed. Make one layer's arrows point the opposite way. That layer records a flip! Then explain what you learned to a friend.

Outro

Cooled lava rocks keep a record of Earth's old magnetic field, like frozen compasses. Science is amazing! What will you discover next? Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!