Tree "Cookies" are used to study climate changes over time.
This image shows two stacks of tree cookies in storage.

 

One way of studying past climates is by looking at the growth rings on trees. Climatic conditions can be inferred by variations in the tree's rings.

 

Widely spaced rings, from when the tree was growing fast, can mean the climate was favorable. Tightly spaced rings can show how a tree grew more slowly. The rings can also indicate avalanche patterns and so much more.

 

United States Geological Survey (USGS) staff collect these tree "cookies" in Glacier National Park, and around the country. Then the cookies must be sanded so the rings can be easily seen and measured.

 

You can learn more about this research here: www.nps.gov/articles/avalanche_research.htm