Changing sea levels

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Pleistocene-several glaciations. 

Distinct ice sheets formed sometimes coming into contact with one another

Britain: 3 distinct glacial advances

Youngest: Devensian (12-71 ka)

Wolstonian (130-200ka)

Anglian (424-478ka)

How do we know this?

Chronology of ice-look at oxygen isotopes in ice cores or deep sea sediments to see where 16O was at the time.

If more 16O (lighter oxygen) in ice cores- less melting after snowfall- locked up in ice. So sea has more 18O. - cooler periods= Higher 18O:16O ratio

If less 16O in ice cores- know moved back to sea via meltwater- climate likely to have been warmer. Sea will have a lower 18O: 16O ratio- enriched with 18O.

Ice ages cause rise and falls in sea level. 

During ice ages- water is stored on land as ice and snow- sea level falls

Deglaciation- increase in meltwater- water returns to the oceans- sea level rises

Sea level processes:

1000s years- ice sheet melts/grow; land motions

10s years: ocean processes, glacial melt/growth. 

evidence sea…


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