• What is the horizontal scale of your graph? Years
• How many years does it show? 1860-2000, It goes by 20 years.
• What is the vertical axis showing? Degrees What are the units? C
• Can you tell from the picture's host page where the data came from? No
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• 1.) There are places that are really hot, and places that are really cold. So I think that the average temperature is around 40 degrees.
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• 2.) I don't think the temperature has changed a lot. 
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• 3.) I think the hottest earth has ever been is around 125. I think the coldest earth has ever been is around -60.  
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• 4.) No

The amount of rainfall effects whether the soil is grassland or forest soil because the grassland gets less rainfall than the forest soil gets.

Grassland does not have as much tree growth. Both forest soil and grassland  soil are fertile for farming, they both have deep soil profiles. 

Forest soil is on the East side of the United States and grassland soil is on the west and south.