Cycles every 400,000 and 100,000 years
- Is it more circular-shaped or more egg- shaped?
- circular: low eccentricity
- oval shaped: HIGH ECCENTRICITY
- obliquity or axial tilt
- changes from 21 degrees to 24.5 degrees
- cycles every 41000 years
- greater tilt, the greater the seasonality
- minimum tilt develops more glaciers
- maximum tilt : warmer summers near poles and less glaciation
- orbital procession
- earth wobbles like a spinning top
- the spin axis sweeps out an imaginary cone
- cycles every 19-23 thousand years
- how do orbital changes show up in the geological record?
- example: changes in tilt
- More tilt = more severe the season
- less tilt = less severe of the season
- effects
- slightly warmer winters
- but cooler summer
- snow from winter doesn't melt
- past glaciation interpreted extended of ice sheets 20,000 years ago
- interpretation temperature variations over the last 100,000 years
- milankovitch cycles with paleoclimate records for the pas million years
- periods of low eccentricity and glacial periods
- showed that procession along with eccentricity and tilt, affects the total amount of insolation
- insolation = exposure to suns rays
- lighter composition absorbs lighter isotopes
- correlation in inferred temperature an co2 concentration
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