Fossil Dating Flashcards
What is fossil dating?
The process whereby the age of fossils is determined
What two methods can be used to determine the age of fossils?
Radiometric dating
Relative dating
What is radiometric dating?
A method of deducing the age of fossils that is based on radioactivity
Which elements have radioactive isotopes?
Uranium
Potassium
Carbon
What is a radioactive isotope?
A substance , the atoms of which have a different number of neutrons to other atoms of the same element
The substance in this form is radioactive
What is a radioactive substance?
A substance which decays into a non-radioactive isotope of another element by releasing nuclear particles
What is a half-life?
It is the rate of decay of a radioactive isotope
What is the rate of decay of an isotope?
The amount of time it takes to break down half of the mass of the radioactive material to its decay product
What are the two methods of radiometric dating?
Direct
Indirect
What is the direct method of radiometric dating?
The radioactive decay of the actual fossil is measured
What kind of fossils is the direct method used for?
Fossils younger than 50 000 years old
How is the age of fossils younger than 50 000 years old measured?
Through carbon dating
How does carbon dating work?
All organisms contain both Carbon fourteen and Carbon twelve
Carbon twelve is a stable isotope
Carbon fourteen is a radioactive isotope
Both isotopes are present in living organisms
All living organisms have the same ratio of carbon fourteen o carbon twelve
By measuring the current amount of carbon fourteen and comparing it to the ratio, you can tell the age of the fossil
What is the indirect method of radiometric dating?
The age of the rocks surrounding the fossil is measured
When is the indirect radiometric method used?
When fossils are older than 50 000 years old
How is the age of the rocks surrounding a fossil determined?
The amount of the original isotopes as well as the amount of the decay product in the rocks sample is measured
It is now possible to determine the age of the rock
What is relative dating?
It is an estimate of a fossil’s age based on the surrounding layers of rock
What is the method used for relative dating?
Palaeontologists study the sedimentary layers above and below a fossil
What is the theory behind relative dating?
The oldest fossils will be lower down
Why is relative dating not the preferred method for determining the age of fossils?
It is not a very accurate form of dating
What is inference?
Deductive reasoning
What is deductive reasoning?
It is when scientists use logical reasoning to make deductions and conclusions from the observations and evidence that is collected
What is deductive reasoning used for?
To understand fossils that are discovered and the history of life on earth
