Absolute Dating (1) Flashcards
What does absolute dating determine?
It determines the ACTUAL age of the specimen in years.
It determines the age of a rock/object using radiometric techniques which uses the half-lives of radioactive isotopes.
Provide some characteristics of absolute dating. (comparison)
It is more specific than relative dating.
provides quantitative data
expensive
time-consuming
requires a particular type of rock or samples
Describe radioactive isotopes
unstable
decay to different elements over time
What is the half-life of a radioactive isotope?
The half-life of a radioactive isotope is the time it takes for half the nuclei of a particular piece of radioactive material to decay
uses logarithmic curve
Name 2 types of radiometric dating
- Potassium-argon
- carbon-14
What does the decay of radioactive potassium (K-40) form?
calcium (Ca-40)
argon (Ar-40)
What can produce potassium (K-40)?
Volcanic lava and ash
Why shouldn’t argon be contained in cooled lava?
As lava comes out of volcanoes, gases, including argon, are released.
Thus, when lava cools to form rock, it should contain potassium but no argon.
Igneous?
What is the half-life for K-40 to decay to Ar-40
half-life of 1250 million years
/1.25 billion years
How can the amt of K-40 and Ar-40 help know the absolute age of the rock?
By measuring the amount of K-40 and Ar-40 now present, we can determine how many half-lives have passed since the igneous rock crystallized, and thus know the absolute age of the rock.
What are the disadvantages of Absolute dating?
It can only be used on rocks of volcanic origin (/igneous?)
To determine the age of the fossil, there needs to be enough suitable rock available to analyse
Available rock needs to be the same age as the fossil.
Accurate from4.3 billion years(the age of the Earth) to about200,000 yearsbefore the present
As only small amounts of argon-40 were detected earlier than 100,000 years, it is not valid for young rocks.
