[Doctor Stochastic]

Ice cores are layered. You can look it up. There are various methods. Besides counting visually (and comparing to annulary tree growth rings), there is a difference in pH between summer and winter depositions so that electrical conductivity can be used. This is good to about 1 or 2 mm. Also one can analyze the H vs D and O16 vs O18 ratios to get temperatures. Various metal residues (Be for example) can be used to date certain parts against known dates. Cores can also be checked with coral cross-sections as well as cores from other parts of the world (Greenland, Siberia, Antarctica.)

There are articles in the usual journals.

[Kay Ludlow]

Ice cores are layered

I understand that completely. My question is how compressed are the layers after the weight of 100,000 years of snow have been on top of them? I would not think that individual years could be distinguished, just broader patterns - more like earth cores than like tree rings. Dig down in the earth and you can see the eons, but only very rarely was there a specific layer that can be certain to have formed in one year (like a volcanic layer). Instead you can see how the earth changed in different periods for sure, but can't determine specific years because of the compression.