Radiocarbon Dating Presentation for Benson's Students

Category: Education

Presentation Description

This is for Benson's students who missed this class. Be sure to print out the handout first.


Presentation Transcript

See handout :

See handout Radiometric Dating


Photo courtesy of the Montana Historical Society 
Figures by Gardell Christensen, 1952 
Background by Dale Livezey, 1988 
Photo by John Smart, 1988 Where is the actual place?


1 mile of cliff

First Peoples Buffalo Jump:

First Peoples Buffalo Jump Formerly known as Ulm Pishkun


Map courtesy of The Defenders of Wildlife 60-75 million bison before European Contact 40,000 Native Americans in MT east of the mtns. What two important things did Indians NOT have before 1700?


Over 300 bison kill sites in Montana Most are NOT buffalo “ jumps ” .


Bearpaw Mountains in northern Montana

Archaeologists want to know . . . :

Archaeologists want to know . . . Who used the site? (which tribes?) When did they use it? (years, seasons) How did they use it?


Courtesy of Canadian Museum of Civilization Corporation


What would be the most abundant type of evidence present at kill sites?


Bone Beds Projectile Points Arrowheads Spear points


Roasting Pits Boiling Pits Stone tools


Used from 900 A.D. to at least 1500 A. D. How do we know?

What scientific technique can be used to establish dates?:

What scientific technique can be used to establish dates? Radiocarbon Dating One type of radiometric dating used to date materials that lived in past 50,000 years

1. What is a “radioactive isotope”?:

1. What is a “ radioactive isotope ” ? An atom with an unstable nucleus that decays (changes into something else) C-14 becomes N-14

2. C-14 has a half-life of 5,730 years. Explain what this means. :

2. C-14 has a half-life of 5,730 years. Explain what this means. Every 5,730 years half the remaining C-14 changes into N-14.


N-14 C-14 5,730 years after death 1/2 of the C-14 has decayed 11,460 yrs. After death After another 5,730 yrs. 3/4 of the C-14 has decayed 17,190 yrs. after death 7/8 of the C-14 has decayed 22,920 yrs. after death 15/16 of the C-14 has decayed


Half-Lives Carbon-14 . . . 5,730 years Iodine-131 . . . 8 days Potassium-40 . . . 1.25 billion years

Potassium - Argon dating (K-Ar):

Potassium - Argon dating (K-Ar) Used on rock that was formed as lava or magma hardened K-40 changes into Ar-40 Half-life is 1.25 billion years


3. What kinds of materials can be radiocarbon dated?


Bones Hides, fur Arrowheads Stone tools Bison feces Charcoal Horns Fire-cracked rock Blowfly pupa


Years Since Death Percentage of C-14 Remaining 40 K O 100 O 10 K 20 K 30 K 10 20 30 40 50 60 70 80 90 1-5,730 2-11,460 3-17,190 4-22,920 5-28,650 6-34,380 7-40,110


1. What percentage of the C-14 would be present in the bone of a wooly mammoth that died 20 kyr ago.

Finish the rest on your own.:

Finish the rest on your own.

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