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One of the more reliable methods of determining regional [#permalink]
21 Apr 2005, 09:40
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One of the more reliable methods of determining regional climatic conditions in prehistoric periods is to examine plant pollen trapped in glacial ice during ancient times. By comparing such pollen samples with spores taken from modern vegetation, scientists can figure out approximately what the weather was like at the time of pollen deposition. Furthermore, by submitting the prehistoric samples to radiocarbon dating techniques, we can also determine when certain climatic conditions were prevalent in that portion of the globe.
Which one of the following may be inferred from the information in the passage?
(A) The earth has undergone several glacial periods.
(B) Radiocarbon dating can be corroborated by glacial evidence.
(C) Similarities between prehistoric and contemporary climates do not exist.
(D) Pollen deposition is a fairly continuous process.
(E) Certain floras are reliably associated with particular climatic conditions.
(E) would be top choice if it were worded as there is at least (this serves as an assumption) one type of flora that can be associated with certain climatic conditions.
I like (D).
If there are abrupt changes in the pollen deposition then carbon dating wont give the time period correctly. So the assumption has to be that "pollen deposition is a continuous process"
anand, Since the scientists are using a sample that is already found in the glaciers to determine climatic conditions, I do not follow why there has to be a continuous pollen deposition.
Am I missing something?
anand, Since the scientists are using a sample that is already found in the glaciers to determine climatic conditions, I do not follow why there has to be a continuous pollen deposition. Am I missing something?
My logic is the following.
Assume climatic period lasts for 100 years. Also assume that the pollen taken for carbon dating is 1000 thousand year old. If the polen deposition were not a continuos process and instead was abrupt then it is possible that all the pollen found for sampling might be at the end of that climatic period.
it is possible that the climatic condition existed 1100 thousand years back.
If the deposition happens anytime within the 100 years then the date could range from 900 thousand years to 1100 thousand years.