# Tree Rings

Subject:
Math
Lesson Duration:
60 Minutes
State Standards:
State: Arizona Subject: Science                     Grade Level: 3-5
SS03-S1C1-02: Recognize how archaeological research adds to the understanding of our past.
SS04-S1C1-04: Describe how archaeological research adds to our understanding of the past.
Thinking Skills:
Remembering: Recalling or recognizing information ideas, and principles. Understanding: Understand the main idea of material heard, viewed, or read. Interpret or summarize the ideas in own words. Analyzing: Break down a concept or idea into parts and show the relationships among the parts.

### Objective

In this lesson students will learn about tree rings and how archaeologists use them to help date sites and artifacts. What are tree rings? How are tree rings used to determine the age of archaeological sites?

Students will...
● Understand how trees grow and why growth rings are formed.
● Describe how climate and weather affects the growth of tree rings.
● Explain the age of a tree by its rings.
● Understand how ring patterns can be used to determine the age of archaeological sites.

### Background

Teachers should review the Tree Ring Background Reading handout ahead of time.

### Preparation

Print copies of the "Tree Ring Background Reading" and "Tree Core Sequences" for students.

Print and cut out teacher copies of the Tree Core Sequences.

Each small group needs: scissors, tape, and a large piece of construction or butcher block paper.

### Lesson Hook/Preview

Which do you think is older: a tree with a skinny trunk or a tree with a thick trunk? Why? Take a poll of the class' predictions.

### Procedure

Step 1: Complete a guided reading using the Tree Ring Background Reading handout.

Step 2: Now the students will investigate tree age by matching similar tree rings. Looking at the Tree Core Sequence Examples handout, we can see that Core Sample F and Core Sample D have a ring that matches. Line up the matching rings, and make sure they always stay in the same curved direction. Core Sample D goes further back to the left so D is an older tree.

Step 3: In small groups or in partners have the students line up from top to bottom the larger core samples A through F in the Tree Core Sequences handout. Students must cut out all six core samples. Arrange them on the paper by aligning matching tree rings. Students will tape them down AFTER you double check. 10-20 minutes.

Step 4: Have students do a “gallery walk” around the room. Rotate around the room seeing if other groups or pairs have the same alignment/timeline. Have students share out any observations.

### Vocabulary

Core: a cylinder of wood taken from the tree

Climate: the average weather in one place over several years

### Assessment Materials

Directions: Line up all six tree rings. It might be a good idea to tape them
together after you think you have the right sequence. It might also be a good
idea to write the year for each ring starting backwards from core F to help

1. When was the first year of growth, the pith, for the oldest tree?
2. If the youngest tree (F) was cut down in 2010, then when was the oldest
tree (E) cut down?
3. The oldest tree was cut down to build the cabin, meaning it was cut down
in the same year the cabin was built or close to that time, so when was
the cabin built?
4. The Nintendo Wii came out in 2006. Which core was cut down in the same year?
5. When was the second oldest tree (C) cut down?
6. Did it get wetter or dryer from the oldest tree to the youngest tree?
7. Write your initials in the tree ring for the year that you were born.

Tree Ring Activity Questions

1) 1996
2) 2000
3) 2000
4) B
5) 2003
6) Wetter