EARTH 002:

GAIA -- THE EARTH SYSTEM

Evidence for Climate Change
Climate will be an underlying theme for the remainder of this course, especially the idea that the climate is subject to significant change in relatively short periods of time. This is an appropriate topic, because climatic change may be occurring today as a result of a combination of natural and anthropogenic (man made) causes. If we are to understand the present, it is useful to understand the past. By studying past periods of climatic change and learning the cause of those changes we are better able to predict the behavior of the earth's climate system. As an introduction to this theme, I would like to present geologic evidence for a dramaitc shift in climate that occurred approximately 15-20000 years ago.
 
 
I. Venetz and Aggasiz -- Ice or Flood
A. A brief look at sediments from streams and glaciers
 
B. A look at other effects of floods and glaciation.
1. Stream erosion
 
2. Glacial erosion
 
C. Surveying the evidence from mountainous regions
 
 
D. Surveying the evidence from northern continents
 
II. Determining a time frame
A. C-14 dating
 
B. The ice cores from Greenland and Antarctica
1. Chemistry
 
2. Stable isotopes
Objectives:

1. Describe differences that you might look for to distinguish stream from glaical sediments.

2. Explain the underlying cause of V-shaped and U-shaped valleys that form by stream and glacial erosion respectively.

3. Give an example of features that indicate more extensive glaciation in mountainous regions.

4. Give an example of features that indicate more extensive glaciation in northern parts of Europe adn North America.

5. Explain how we can determine the age of glacial advance and retreat.

6. Relate the ratio of stable isotopes of oxygen in ice to the amount of ice stored in glaciers.

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