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Dating Past Climate - Coggle Diagram
Dating Past Climate
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Ice Cores
Ice cores are useful climate proxies, as the ice contains tiny bubbles of air trapped during the initial ice formation.
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The relative frequency of hydrogen and oxygen atoms with stable isotopes can be measured. This can be used as a climate proxy as the lower the frequency of isotopes the colder the climate.
16O evaporates more easily than 18O, so when water evaporates from ocean it leaves more 18O behind.
Lake Sediments
may contain: pollen grain, spores, diatioms, varves
Pollen Grains
Pollen analysis can be used to show past vegetation types and in turn can be used to infer palaeoclimatic conditions.
Diatoms
Diatoms are microscopic plants found preserved in lake sediments. They are particularly useful for past climate studies because of their sensitivity to different conditions “indicator species”. They are made from silica (SiO2) which helps them preserve well in the fossil record
Varves
These are tiny layers of lake sediment made up of light and dark bands. The light bands are formed of coarser sediments from in spring and summer from higher energy melt-water run off. Darker bands are made up of fine sediment and show deposition in the winter months when lake surfaces are frozen.
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Tree Rings
The study of tree growth rings (annules) can enable us to date past events such as climate change. Each annule marks a year in the tree’s life and represents a complete cycle of seasons of growth.
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By studying these rings and their width it is therefore possible to identify and date climate changes.
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Seafloor Sediments
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These consist of shells of calcium carbonate and it is the chemical composition of these shells which can tell us the sea level, temperature and ocean conditions from millions of years ago.
Fossils
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Some species are particularly sensitive to moisture and temperature fluctuations and where these can be found in the fossil record they can therefore be used as proxies for climate.