deep time 2

Question 1

unstable isotopes

Answer 1

Many isotopes are in an unstable energy state
They will “decay” to gain a more stable state
Decay
-Emission of particles and energy to become more stable
Parent isotope
-Atom that decays
Daughter isotope
-Isotope that results from the decay

Half life: time it takes for half the isotopes in a group to decay into daughter isotopes

ex: Parent Potassium-40 (40K) decays to daughter Argon-40 (40Ar)
Half-life = 1.25 billion years

Question 2

half life

Answer 2

The time it takes for half the parent isotope to decay into the daughter isotope
Example: Carbon-14
Half-life: 5730 years
14C decays to 14N
After 5730 years, half of the 14C is now 14N
After 11,460 years
75% of the 14C is now 14N
After 17,190 years
87.5% of the 14C is now 14N

cab’t use carbon 14 in geology because it’s not old enough
after two half lives you have 1/4. You take half of remaining isotopes in second half life: theoretically: you can never get to zero. in reality after 1 your down to zero(can’t be 1/2)

Question 3

Radioactive Dating

Answer 3

Age determination
- Measures the ratio of the parent-to-
daughter isotopes
Analytical precision and the right minerals
from table screen shot now rb, k, u ones. don’t memorize half lives of them

Question 4

Confused by radiometric age determination? Hoped there would be no math in this class? Have no fear, your radiometric cheat sheet is here!

Answer 4

see screen shot

Question 5

half life calculation example: You have a rock that, upon careful analysis, has only 1/16 of the original Fake Isotope remaining. Fake Isotope has a half-life of 1.28 million years. How old is your rock?

Answer 5

it takes 4 half lives to get to 1/16
1.28x4= 5.12 million years

Question 6

relative dating: see screenshot and try to put them in order

Answer 6

EGLCHMDJANKBF

Question 7

isotopes

Answer 7

Change the number of neutrons
Same element, different isotope
Example: Helium
Atomic number: 2
Total of neutrons and protons: 4 – in the idealized element
This would be known as the 4He isotope
Other helium isotopes
3He = 2 protons, 1 neutron
6He = 2 protons, 4 neutrons

Question 8

small dots on relative dating map show

Answer 8

baked rocks around intrusion, wherever baked marks stop that rock is younger than the intrusion their meeting is an incomformity between crystal and rock ; rocks with baked marks are older than the intrusion no matter how deep it reaches

Question 9

angles that don’t match up on relative dating map

Answer 9

angular uncomformity