The radioactive element Unobtanium-189 (Ut-189) decays to the stable element Dilithium-171 (Di-171). The half-life of Ut-189 is 10 million years. Using a very sensitive atom-counter instrument, you determine that a mineral sample has 150 atoms of Di-171, and 50 atoms of Ut-189. Assume that no atoms have been lost due to metamorphism over the lifetime of the rock.

 How many half-lives have passed since the mineral formed?

1

2

4

The radioactive element Unobtanium-189 (Ut-189) decays to the stable element Dilithium-171 (Di-171). The half-life of Ut-189 is 10 million years. Using a very sensitive atom-counter instrument, you determine that a mineral sample has 150 atoms of Di-171, and 50 atoms of Ut-189. Assume that no atoms have been lost due to metamorphism over the lifetime of the rock.

 What is the age of the mineral?

10 million years old

20 million years old

30 million years old

Not using the examples in the text, how would you create a piece of art to illustrate the passage of time?

List the five most significant things that happened in the world in the last 100 years. Place them in chronological order starting from earliest to most recent, but don’t worry about giving the exact dates when they occurred.

Using what you have learned so far, make a list of 5 geologic events or phenomena and place these items in the correct chronological order, from earliest to most recent. Include the dates of these events where possible.