L6. RADIOMETRIC DATING Flashcards
a method used for sequencing rock layers, fossils, and geologic events of the earth
RELATIVE DATING
determines the sequence of events and their relative ages, but does not provide a specific numerical age.
RELATIVE DATING
Uses the following:
- Stratigraphy
- fossil correlation
- the principle of cross-cutting relationships
RELATIVE DATING
Example: Determining that one rock layer is older than another based on their position in a sequence.
RELATIVE DATING
a method used to date materials by comparing the abundance of a radioactive isotope to its decay products
ABSOLUTE DATING
crucial for determining the age of archaeological and geological specimens.
ABSOLUTE DATING
Radioactive Isotopes (6)
Carbon-14 (C-14)
Potassium-40 (K-40)
Uranium-238 (U-238)
Uranium-235 (U-235)
Rubidium-87 (Rb-87)
Thorium-232 (Th-232)
Half-life: 5730
Usage: Organic remains up to 50,000 years
C-14
Half-life:4.5 billion
Usage: Old rocks and minerals
U-238
Half-life: 1.25 billion
Usage: Geological dating
K-40
Half-life: 49 billion
Usage: Ancient rocks
Rb-87
Half-life: 14 billion
Usage: Geological processes
Th-232
Purpose: date relatively recent organic materials (e.g., bones, wood)
CARBON-14
(C-14)
Range: effective up to about 50,000 years old.
CARBON-14
(C-14)
Use: date artifacts and remains of once-living things.
CARBON-14
(C-14)
Living organisms have the same ratio of ___ to ___ as found in the atmosphere
C-12, C-14
- Decays into Lead-207.
URANIUM-235
the amount of time it takes for half of a sample of that substance to decay or reduce by half.
HALF-LIFE
- Useful for dating relatively young rocks (in geological terms) and minerals up to around 1 billion years old.
URANIUM-235
Decays into Lead-206.
URANIUM-238
Ideal for dating older geological formations, such as rocks billions of years old.
URANIUM-238
Decays into Argon-40
POTASSIUM-40
Best used for dating igneous rock, ancient geological events, such as the formation of mountain ranges or crustal evolution
POTASSIUM-40
Decays into Strontium-87
RUBIDIUM-87
Has a half-life of about 48.8 billion years, one of the longest half-
lives among radioactive isotopes
RUBIDIUM-87
suitable for dating extremely old rocks, from millions to billions of years old.
RUBIDIUM-87
Decays into Lead-208
THORIUM-232
suitable for dating extremely old rocks, from millions to billions of years old.
THORIUM-232
What dating method will you use to date a rock that is estimated to be around 1 billion years old?
ABSOLUTE DATING
(POTASSIUM-40 to be more specific)
A fossil is estimated to be around 100,000 years old. Can carbon-14 dating be used?
No.
Because it is only effective up to about 50,000 years old.
oldest fossil ever dated
stromatolites
the remains or imprint of an organism that lived during a specific geological time period
index fossil
used by scientists to identify and correlate the ages of rock layers (strata) in different locations.
index fossil
How old is the Earth
4.5 Billion years
Another name for neutron
gluon
4 forces
Gravity
Electro magnetic
Strong nuclear force
Weak nuclear force
cyanobacteria
stromatolites
Age of oldest fossil
3.5 billion years old
Age of oldest mineral
4.4 billion years
Oldest mineral
Zircon
