•Time and Change Flashcards
Law of superposition
Rocks that lie above other rocks are younger in age
Law of cross-cutting relationships
Rocks that cut across others must be younger
Law of included fragments
Fragments of rock included in the hose rock must be older than the host e.g at an uncomformity
What are the 6 factors that make a good zone fossil?
1) evidence of rapid evolutionary change
2) large population so common
3) wise geographical distribution
4) ready preservation
5) high facies independence (variety of environments)
6) distinct features
What are the two main groups of zone fossils?
Graptolites
Ammonoids
What is radiometric dating?
Absolute dating
Based on the fact that unstable elements decay or change into more stable elements at a stable rate
What is a proton?
Positively charged particle
What is a neutron?
Particle with no electrical charge
What is an electron?
Tiny particles of negative charge that orbit the nucleus of the atom
What is the half life
Half the time taken for the parent atoms in a mineral to change into daughter atoms
What is potassium argon dating?
Based on the fact that the radioactive isotope of potassium 40 decays into the gas argon 40
What is the limitations of potassium argon dating?
Metamorphism- can contaminate rocks with more potassium 40 which makes it look younger
Weathering/erosion- releases the gas to make it look older
Samarium-Neodymium Dating
Sm147 is a radioactive isotope and decays into Nd143. Has a half life of 106 billion years
Compare the amount of Nd143 with the stable element of Nd144
Time periods
Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Pre-Cambrian
