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What do sediments form over time?
Horizontal layers
According to the Law of Superposition where are the oldest rocks?
At the bottom
According to the Law of Superposition where are the youngest rocks?
At the top
What type of rock forms from compacted sediment?
Sedimentary rock
What method gives the exact age of a fossil?
Absolute dating
Which dating method uses radioactive isotopes?
Radiometric dating
What does relative dating tell us?
Which fossil or rock is older or younger
What does absolute dating tell us?
The numerical age of a rock or fossil
What is the oldest known type of fossil?
Stromatolites
What created stromatolites?
Cyanobacteria
About how old are stromatolites?
2 billion years
Where in Australia are stromatolites found?
About 100 km north of Perth
Why are stromatolites important?
They show early life and oxygen production on Earth
What does the Law of Superposition help scientists determine?
The relative age of rocks and fossils
Which isotope is used for dating very old rocks?
Uranium-238
