module 3- absolute dating

Question 1

how do we date geologial materials and events?

Answer 1

• use radioactive elements
  isotopic dating
  -radioactive isotopes decay (protons and neutrons leave randomly).
  -they have a proportional decay rate and a half life
  produces a unique parent and daughter isotope
• analysis can be used to determine planetary age
• measure amount of parent isotope and daughter element in rock, then calculate amount of parent isotope in the rock when formed, then using half life, calculate age
  -tungson isopte used to date formation of earth and stars

Question 2

what assumptions are made in radiometric dating

Answer 2

• system has stayed closed (no daughter product escaped) (no erosion)
• no daughter product present initally
• enough parent and daughter product atoms to measure (ex. recent materials dont have enough carbon produced to measure)

Question 3

what are the best isotopes to use for dating

Answer 3

• those commonly found in rock forming materials (eg. K40 occurs in micas, feldspots, and hornblends)
• those with unique daughter products (some isotopes can produce different daughter products depending on envionment- these are not useful because we need 1 parent and 1 daughter)
• uranium238

Question 4

why are zircons commonly used in geochronology

Answer 4

• common igenous rock
• hard and resistant to erosion
• have trace amounts of uranium and thorium
• oldest dated material on earth

Question 5

what are the best rocks to carbon date

Answer 5

-igenous rock
-lava flows
- as soon as fock has formed (when it is solid, crystal structure and chemial structure are set), radioactivity begins
- second best is metamorphic

Question 6

lava vs magma

Answer 6

• lava: molten rock that has emerged into the surface of the earth
• magma: molten rock inside of earth