Geography Palaeoclimatic Indicators
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38 Terms
Uniformitarianism
the idea that present physical processes have always operated the same way
What can we do with uniformitarianism?
extrapolate backwards in time and deduce what past conditions were like
Proxy
a preserved physical, chemical, or biological natural recorder of past climates/conditions
Law Of Superposition
where within the core, the age of sediment or ice is in relation to its depth
What is an ice core?
cylinder of ice drilled out of an ice sheet or glacier
Where are ice cores most commonly found?
greenland and antartica
How long was the longest ice core?
3km
How old was the oldest ice core in Greenland?
123,000 years
How old was the oldest ice core in Antartica?
800,000 years
Examples of indicators:
carbon dioxide, oxygen isotopes, pollutant concentration, electrical conductivity
How far to direct instrumental records go?
150 years
Are direct instrumental records recorded globally?
yes
What are the negatives of direct instrumental records?
only go back 150 years, estimation required for areas without direct reading, some debate over correct readings.
What two things does a Proxy require?
a reliable indicator of climate conditions and a reliable method for dating
Give one reliable indicator of climate conditions.
Temperature
What is dendroclimatology?
Using tree rings to reconstruct past climates
What do wide tree rings mean?
rapid growth and so warm, wet conditions
What do thin tree rings mean?
slow growth and so cool or dry conditions
What does the use of tree rings as a proxy require?
averages across trees
How far back do living trees provide?
few hundred years
How far back does structural timber provide?
1,000+ years
How far back does preserved bog trees provide?
up to 5,000 years
How are ocean sediments and microfossils formed?
marine sediment layers over time and conpressses
How can species be used in ocean sediments/microfossils?
different species thrive in specific water temperature ranges
How can shell material be used in ocean sediments/microfossils?
chemical analysis of the shell material to find water temperature
How are ice cores formed?
unmelted snow forms ice under pressure
How far do trapped air bubbles record in ice cores?
up to 500,000 years
How are annual layers formed in ice cores?
summer/winter texture changes or summer sunlight sublimation
A higher concentration of heavy water isotopes indicate what climate?
warm temperatures
A higher concentration of light water isotopes indicate what climate?
cooler temperatures
Why does pollen act as a biological proxy for past climate change?
preserved pollen grains in sediment layers reveal shifts in historical plant communities
Three pros of pollen as a proxy
pollen types indicate the vegetation types, relative data can be carried out, can be collected from many environments
Three cons of pollen as a proxy
other factors affect plants so cannot isolate temperature, sediment layers can be disturbed or missed, wind and water can transport pollen from its native area
What is relative dating?
doesn’t find exact act of sample, instead finds two bounds
What is absolute dating?
get an exact date, often done through radiocarbon dating
What does absolute dating/radiocarbon dating require?
carbon/organic compound
Pro of absolute dating
more accurate
Cons of absolute dating
more expensive, less accessible