Relative + Absolute Age

Question 1

What is the Law of Superposition?

Answer 1

Each rock layer is older than the one above it. The deeper you dig, the further back in time you can see.

Question 2

What is relative age?

Answer 2

The age compared to the ages of other rocks. The Law of Superposition can be used to find the relative age of rocks

Question 3

What are index fossils?

Answer 3

Fossils that help geologists match rock layers. They are widely distributed in rock and represent organisms that existed for a short geological time period.

Question 4

What can index fossils tell us>

Answer 4

The relative age of rock layers in which they occur.

Question 5

What is relative dating?

Answer 5

How old rock is compared to other rocks.

Question 6

What are the 2 ways to express the age of rocks?

Answer 6

Relative age and absolute age.

Question 7

What is absolute age?

Answer 7

Number of years that passed since rock formed

Question 8

How is absolute age calculated?

Answer 8

By using radioactive dating.

Question 9

What is radioactive dating.

Answer 9

Scientists use the rate at which elements decay within the rock to calculate the age.

Question 10

How does radioactive dating work?

Answer 10

As radioactive elements within the rock decays, it changes into a different element so the composition of a rock changes over time.

Question 11

What is a half life?

Answer 11

Rate of decay of a radioactive element-time it takes for half of the radioactive atoms to decay. It decreases at an exponential rate.

Question 12

What is carbon dating?

Answer 12

Type of radioactive dating used to determine absolute age.

Question 13

How does carbon dating work?

Answer 13

Plants and animals contain carbon, including carbon 14. After the organism dies the carbon 14 in the organism’s body decays and changes into a different element.

Question 14

What is used to date fossils of prehistoric mammals?

Answer 14

Carbon 14, but it can only be used to date fossils/rocks younger than 50,000 years old.

Question 15

Iodine-125 has a half life of 60 days. Let’s say you start with a 50 gram sample. How much would be left after 4 half lives.

Answer 15

50 g > 25 > 12.5 > 6.25 grams
You would be left with 6.25 grams

Question 16

What fraction of Carbon-14 would be left after 8 half lives?

Answer 16

1/2 > 1/4 > 1/8 > 1/16> 1/32 >1/64 > 1/128 > 1/256
You would have 1/256 remaining after 8 half lives.

Question 17

What is absolute dating?

Answer 17

The actual number of years since the rock formed (radiometric dating/ half life calculations)