Unit 2 Lesson 3

Question 1

Absolute dating

Answer 1

Determining the actual age of an event or object

Only works for igneous rocks

Fossils can help determine the absolute age of sedimentary rock

Question 2

Ways to find the absolute age

Answer 2

1. Using radioactive isotopes
2. By radiometric dating
3. Radiocarbon dating

Question 3

Radioactive decay

Answer 3

The breakdown of a radioactive isotope into a stable isotope of the same element or of another element

Question 4

Half-life

Answer 4

The time needed for half of a sample of a radioactive substance to undergo radioactive decay to form daughter isotopes

Question 5

Radiometric dating

Answer 5

Finding the absolute age of a sample by determining the relative percentages of a radioactive parent isotope and a stable daughter isotope

Question 6

Radiometric dating methods

Answer 6

1. Radiocarbon dating
2. Potassium-Argon dating
3. Uranium-Lead dating

Question 7

Index fossils

Answer 7

Act as markers for the time that the organism lived on earth

Organisms that formed index fossils lived during short periods of geologic time

Rock layers that contain index fossils can be dated accurately

Question 8

Uranium - Lead Dating

Answer 8

Uranium-238 decays to lead-206

Based on measuring the amount of lead - 206 daughter isotope in a sample.

Can be used to determine the age of igneous rocks between 100 million years and billions of years old

Question 9

Potassium - Argon Dating

Answer 9

Potassium-40 decays to calcium and argon. The half life is 1.25 billion years

Based measuring argon as the daughter isotope

Can be used to date igneous volcanic rock between 100,000 and a few billion years old

Question 10

Radiocarbon Dating

Answer 10

can only be used to date organic matter that lives in the last 45,000 years