Dating Rocks! Why Date the Rock Around a Fossil?

What Crafty Clover says in this video

Intro

Hi! I'm Crafty Clover! Let's discover something amazing. WHY DO SCIENTISTS DATE THE ROCK AROUND A FOSSIL?

The Big Idea

Most bones don't come with a clock inside them. So how do scientists know how old a fossil is? The rock layers above and below it can be dated. Think of a sandwich. Date the bread, and you learn about the filling! The rock is the calendar, and the fossil is the event.

Step 1

Number one: note the layer. Scientists write down exactly which layer of rock the fossil was found in. Layers on the bottom are usually older than layers on top.

Step 2

Number two: date the rock nearby. Some layers, like volcanic ash, have crystals that work like tiny clocks. Labs measure them to find out how long ago the layer formed.

Step 3

Number three: place the fossil in the window. If the layer below is older and the layer above is younger, the fossil fits between them. Scientists write the uncertainty too, with the word about.

A Closer Look

Let's look at the layers of rock. The ash bed on top can be dated. The fossil layer sits in the middle. And the older rock below gives the other end of the window.

Quick Facts

Quick facts! Some rock layers can be dated to millions of years ago. The window can be wide, so scientists say about, and not an exact year. Usually, younger layers sit on top of older ones. Scientists often date the ash instead of the bone, because the ash has the crystal clocks.

Think Like a Scientist

Now, think like a scientist! Stack five different colored books, or slices of bread, in a pile. Which was put down first? Which is the oldest? Then ask, why date the ash and not the bone? And what does a wide window still tell you?

Outro

Rocks keep time, and scientists read the calendar to date a fossil! Crafty Clover can be found on Amazon Books, Google Bookstore, and Apple Books. Available for purchase or download! Bye for now!