Warm Up, October 2nd, 20131) C-14 has gone through how many

half-lives if it’s about 23,000 years old? What % is left if it starts at 80%?

2) What has NOT happened to over 99% of life on Earth?

3) What 3 criteria make up a good Index Fossil?

4) What can ice cores tell us about Earth of the past? (2 examples)

Looking at a clock? Absolute

Looking at sedimentary layers? Relative

Looking at an index fossil? Relative

Measuring C-14? Absolute

5 + 5 Absolute

Geologic Time• The scale scientists use to determine

the order of events and when they took place on Earth.

How do we measure Geologic Time?

• In several sections:– Eons (biggest)– Eras– Periods– Epochs (smallest)

Precambrian Eon Phanerozoic Eon

• Most of Earth’s history• 4 Billion Years• No large life (microscopic)

• Very little of Earth’s history• 500 million years• Larger life begins (non-microscopic)

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Speaking of microscopic life…Is it possible to have fossils of singlecelled life?

Why or why not?

Radioactive Decay• What do you associate these words

with?

Half Life Worksheet - Partners

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Study Guide

Begin now, due Thursday(Yeah, that’s tomorrow)