The History of the Earth: Supplemental Guide 8A | Dinosaurs 149

Introducing the Read-Aloud 10 minutes

What Have We Already Learned? 5 minutes

Review with students that a fossil can be either the preserved

body or the imprint of a plant or animal that lived long, long ago.

Explain that even though paleontologists are interested in the

history of life on earth, they still need to know a lot about geology

in order to determine how old fossils are and where they fi t in the

history of life on earth. Remind students that the soil and rocks

are divided into layers, and that the layers represent different

geologic times when changes happened to the crust of the earth.

Tell students that we determine how old certain fossils are based

on our understanding of geology and rock layers. Use Image

Cards 10–13 to talk about the order in which these living things

inhabited the earth.

Vocabulary Preview 5 minutes

Excavating

 Show image 8A-4: Excavating dinosaur bones

1. Today you will hear how paleontologists fi nd dinosaur fossils
   by excavating—or digging up—their bones.


2. Say excavating with me three times.


3. Excavating is making a hole to uncover something by digging.


4. Excavating dinosaur bones is a slow and careful process.
   Rocio thinks that excavating dinosaur bones is like digging for
   treasure.


5. Who do you see in this picture? What is this person doing?
   Do you think excavating dinosaur bones is an easy job or
   diffi cult job? Is it a slow process or a fast process? [Point out
   how the paleontologist is using a very small tool to chip away
   sedimentary rock that is attached to the dinosaur bone.]

DDinosaursinosaurs

8 A