Dendrochronology
Dendro = tree, chronology = dating
Dendrochronology, or tree-ring dating, is a technique archaeologists use to determine the age
and environmental conditions of a site when it was occupied. Tree rings keep a record of
certain events and environmental changes during its growth. Each tree tells the story of its life!
Telling the story of climate
Every year, a tree forms a new ring
around its center during the warm
growing season.
Depending on the climate and
environment the tree is living in,
the thickness of the rings varies.
During a rainy season, a ring is
thicker and during a dry season or
drought, a ring is thinner.
Sometimes the rings show
evidence of a forest fire.
Photo: https://climatekids.nasa.gov/tree-rings/
Why do you think it is important for archeologists to know what the climate was like for the
people of the past? What can it tell us about the way people lived?
Telling the story about age
Trees can tell us which years were dry
and which years got more rain when
they were growing, but they can also
help archaeologists pinpoint specific
numerical dates (absolute dating)
when they lived. Because each year
adds a new ring, as long as you have a
known tree sample, you can count
back the rings to see how old an
unknown sample is exactly. In the Southwest this continuous timeline goes all the way to 322 BC!
Use dendrochronology to determine these dates in history!
The strips on the following page represent core samples taken from trees. Each sample shows
the growth rings for that particular tree indicated by each line. By lining up matching patterns
of the undated samples with the patterns on the dated sample, you can count back and
determine dates for each of the events in history labeled on the cores.
You will need:
Core samples from the following page
Scissors
Glue or tape
What to do:
1. Print and cut out all the cores on the following page. Be sure to leave on the labels when
cutting.
2. Each of the cores reveal different moments in time. Overlap each strip and look for and
line up matching patterns to create a timeline.
3. When all the patterns of the tree rings line up, tape/glue down each strip.
4. Once you have your timeline, count back each year on the strips to date when each
event took place.
Core Sample # Age of Tree Year Growth Began Year Cored
1
2
3
4
What year did each labeled event occur?
Women achieved the right to vote: ___________________________
New Mexico became a state: _________________________
Maxwell Museum of Anthropology was founded: _________________________
A.E. Douglass develops Dendrochronology: _______________________
Roswell UFO Incident: _________________________
Check the key below for answers.
Women achieve
the right to vote
Core #4
UFO reported
Maxwell Museum
in Roswell NM
is founded
Core #3 1957
A.E. Douglass
develops
Dendrochronology
Core #2
New Mexico
becomes a state
Core #1
Tree of Life
The story of a tree’s life is told in its rings and for this activity you are going to make your very
own tree rings to tell your story and show what your growing seasons look like!
You will need:
A paper plate
A pen
1. To begin, draw a circle in the middle of your plate
and write your first year growth/the year you
were born.
2. Add 1 ring around the center for every year
you’ve been alive. Years you don’t have much
memory of or have bad memories of are dry
years. Years with good memories which were full
of growth are rainy years. The better a year, the
thicker the ring.
3. Write landmarks which stand out between the
lines. For example: the first day at school, winning
an award, moving houses, etc.
4. Continue to add rings until you have reached your
current year.
Discussion Questions:
- How was your tree impacted by your environment?
- How does your tree compare with others in your environment?
Key
Core #1
Core #4
Core #2
Core #3
Women achieved the right to vote: 1920
New Mexico became a state: 1912 Core Sample # Age of Tree Year Growth Began Year Cored
Maxwell Museum of Anthropology was founded: 1932 1 24 1910 1934
2 28 1926 1954
A.E. Douglass develops Dendrochronology: 1929 3 31 1926 1957
4 38 1914 1952
Roswell UFO Sighting: 1947
Resources:
Dendrochronology from PBS Time Team America
http://www.pbs.org/time-team/experience-archaeology/dendrochronology/
Dendrochronology from Crow Canyon Archaeological Center
https://www.crowcanyon.org/index.php/dendrochronology
Tree Rings Simulation – Dendrochronology from UCAR Center for Science Education
https://scied.ucar.edu/interactive/tree-ring
Life as a Tree from Scishow Kids
https://www.youtube.com/watch?v=MwNJC-IRgPE
What Can Trees Tell Us About Climate Change? From Climate Kids - NASA
https://climatekids.nasa.gov/tree-rings/
Dendrochronology from Southwestlearning.org, NPS
https://www.nps.gov/tont/learn/nature/upload/Dendrochronology_Overview-Copy-2.pdf
Dendrochronology: What Tree Rings Tell us About Past and Present, from
Environmentalscience.org
https://www.environmentalscience.org/dendrochronology-tree-rings-tell-us
Lulu grateful for all that trees give us (especially paper!) PLANT A TREE!
