Name ____________________________ Date ______________ Period ________
Biology
Unit 6 – Biodiversity/Evolution, Background Paper 6-9
Dating
Sorry – not a lesson on how to get someone to go out with you. This reading is about how we know what age
to put on a fossil or artifact. When someone says that such and such is xxx,xxx,xxxx years old, how do we know? I have
heard people challenge proposed dates with, “How do you know, no one was there?” Not much of a challenge really.
Ever look at a tree stump and count the rings? How did you know the tree was a certain age? You weren’t there were
you? The type of dating you did on the tree stump is called dendrochronology and is just one of many dating methods
(dendrochronology can be used to date items as far back as 11,000 years with precision). Several methods must be in
close agreement in order for the proposed date to gain acceptance. Dating methods fall into two categories; relative
dating and absolute dating. Relative dating methods tell you that something is older or younger than something else. It
doesn’t tell you how much older or younger. Absolute dating fixes a time on the item in question. The purpose is not
for you to remember all of these techniques but to realize that when a date is placed on a fossil it is not some random
guess but a careful crosscheck of multiple methods available to determine when something occurred even though you
weren’t there to see it.
Relative Dating Techniques
(remember, it only tells you if one item is older or younger than another)
Cation Ratio – Used to date surfaces that have chemical deposits on them (like a toilet ring)
Cultural Affiliation – Used to date artifacts associated with particular human cultural periods
Fluorine Dating – Used to compare the age of different bones at the same site
Obsidian Hydration – Used to date stone tools made from volcanic material
Patination – Used to date items that have been chemically altered in the ground
Pollen Analysis – Pollen is very resistant and can date items up to 400 million years ago
Rate of Accumulation – Used to date items found in rock or soil deposits
Seriation – Used to date cultural artifacts by the level of technology used to make them
Varve Analysis – Like counting rings in a trees, this method counts annual sediment in lakes
Absolute Dating Techniques
Archaeomagnetism – Dating using the changes in the earth’s magnetic fields
Astronomical Dating – Used to date items influenced by the position of celestial bodies
Dendrochronology – Counting tree rings in living, dead, or fossilized trees
Ice Core Analysis – Counts the annual accumulation of ice in glaciers and icecaps
Electron Spin Resonance – Measures the amount of crystal structure in an item
Fission Track – Measures the number of tracks created in an item by radiation over time
Optically Stimulated Luminescence – Measures how long an item has been out of contact with sunlight
Oxidizable Carbon Ratio (OCR) – Dates items by measuring the chemical reactions that affect carbon
compounds
Potassium- Argon Dating – Measures the rate at which radioactive decay occurs
Racemization - Dates by measuring the changes in Amino Acids in once living organisms
Radio-Carbon Dating (Carbon-14) – Dates by measuring the changing ratio of different carbon atoms once
an organism dies
Thermoluminescence Dating – Dates items that may have been heated (pottery, hearths)
Uranium-Thorium Dating – Dates long stretches of time using radioactive decay ratios
Background 6-9,BiodiversityEvolution2012
Text 2012
Greg Ballog
Page 1
Name ____________________________ Date ______________ Period ________
Title of Reading: 6-9 Dating
Points Earned
1 2 3 4 5 6 7
Concept Map of Reading (3 points)
Main Idea
A) What one question do I have about this article?
1 Point
A&B
B) Show or describe the reading to a parent or guardian (Name ___________________).
What comments or questions did they have concerning the reading?
(Biology Homework Time __________)
Background 6-9,BiodiversityEvolution2012
Text 2012
Greg Ballog
#
1
2
3
Answers
Page 2