Tree Rings Coral Rings
Ice Cores Lakes and Ponds, Varves, and Pollen

In climate studies, obviously one of the most important aspects is the ability to constrain a time period. For example, many climatologists study deep lakes that show pairs of layered sediments indicative of seasonal deposition throughout the year.  There sediment couplets, known as varves, show light colored sediments that are often washed into a lake during the spring melt, topped by a darker material that contains organics from a summer algal bloom. Varved sediments therefore lend themselves well to biological, chemical, and mineralogical testing that can indicate very specific yearly data about climate and environmental change.


Photograph of an outcrop containing a thick section of Pleistocene age varves, Scarboro Cliffs, Toronto, Ontario, Canada.
The largest of the varve couplets are more than 0.5 inches thick.



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