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# Tree Rings, Ice Cores, and Varves

## Scientists can determine absolute ages using tree rings, ice cores and varves.

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Ice Cores

### Ice Cores

Credit: PD-USGOV-DOC-NOAA
Source: http://commons.wikimedia.org/wiki/File:Icecore_4.jpg

The Antarctic ice cap contains a tremendous amount of information about Earth during the past 1.5 million years. Scientists have only to collect the ice, analyze it and then learn what it has to say. Of course, that’s not so easy!

#### Why It Matters

• Information in ice cores can include radioactivity, air pollution, sea storminess, age, climate, temperature, volcanic activity.
• Scientists have a 800,000 year ice record and are hoping to get a 1.5 million year old ice record from Antarctica.
• Carbon dioxide levels are higher now than they have been in the past 800,000 years.
Source: http://en.wikipedia.org/wiki/File:Taku_glacier_firn_ice_sampling.png

Scientist gathering snow and ice samples - see fresh snow above the glacier ice (bottom of the pit wall)[Figure2]

#### Explore More

1. What are the three features of an ice core that can give information to scientists and what is that information?
2. How do scientists know that the layer of ice they are looking at was deposited in 1883?
3. What is the relationship between temperature and carbon dioxide content in Antarctic ice going back 800,000 years? At what time period is CO2 highest?
4. How do scientists tell annual layers in an ice core?
5. What nuclear events can be seen in ice cores from near the South Pole?
6. What can scientists tell from measuring the hydrogen isotopes of methane?

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