Definitions
from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun A layer or series of layers of sediment deposited in a body of still water in one year.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun geology An
annual layer ofsediment orsedimentary rock .
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
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Examples
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Preserved records of ecosystem variations (e.g., trees, fossils, and sedimentary deposits), combined with dating techniques such as carbon-14, lead-210, or ring/varve counting, have been a primary source of information for unraveling past environmental changes that pre-date the age of scientific monitoring and instrumental records.
Historical changes in freshwater ecosystems in the Arctic 2009
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The average varve thickness is 3.7mm while the post-1945 thickness increases to greater than 10mm, coincident with a 1957 drop in lake level of 26m.
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More telling is the strong correlation of varve thickness with an updated temperature
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Clearly if the shoreline is changing, then distance to the core sites from sediment sources for the summer part of the varve is changing.
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Being a simplistic kind of fellow myself, I thought Why are they comparing varve thickness to tree rings and global temperature?
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It is an interesting question, though, why varve thickness would be inversely correlated with both temp and precipsummer cloudiness perhaps?
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Associated with density flows are suspended sediment clouds responsible for the “Bouma” sequence and which will undoubtedly contribute to anomolous varve thickness in proximity to the flow.
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Because of this, the stations I have looked at should have a positive correlation with the varve data.
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Hence you can in theory introduce changes in varve thickness with no changes in runoff i.e. summer temperature.
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The recent qualitative change the glacial floods and perhaps the possibly-real qualitative difference in the modern minimum thickness varve frequency, lend support to the idea that something in recent years is different from the rest of the record.
bilby commented on the word varve
"Each of these layers defines an annual accumulation of sediment. Varved sediments may contain dropstones, which are fragments of rock that have dropped from an overlying floating ice sheet and that have sunk into and depressed the layers beneath them."
- Encyclopaedia Britannica.
October 2, 2008