Cycles Flashcards
(47 cards)
What is dendrochronology?
the study of tree rings to date past events and areas
What do tree rings represent?
Annual growth/ seasons/ growth conditions
How ill tree rings reflect the seasons?
Less dense in summer due to better growth conditions
Dense in winter with worse conditions
How long can trees be used to date?
~14,000 years
What do ice cores record?
CO2 and temperature
What is the length of glacial seasons?
~100,000 years
What was the climate 20,000 years ago in europe?
Glacial
How do ice cores represent time?
Will creating banding of snow layers which trap gas bubbles of that atmosphere at that time
How far back can ice cores be used to date?
~1 million years
What can be seen with in the Mediterranean rock record which shows cycles?
Prominent rhythmic alterations in rock type in marine and lake sediments
What does the presence of high frequency switches of sediment colour and bundling show?
Multiple cycles occurring at once
Why are lakes and river sediments less likely to show signs of cycles?
Lakes affected by uplift and tectonics
Rivers are highly dynamic
What other type of core can cycles be seen in?
Marine cores
What did Luis Agassiz propose?
extinction of the Pleistocene megafauna was due to widespread and deep “winter”
What gave evidence in glacial environments that glaciers had once been larger?
Erratic’s and moraines being seen at higher elevations
What did the realisation of greater glacial extent provide a new explanation for?
Erratic’s and other glacial features across N. Europe and N. America
Who was Milutin Milankovitch?
A Serbian engineer and meteorologist who worked on a mathematical theory of climate
What did Milankovitch calculate?
Seasonal variations in the amount of solar radiation received by the Earth were dependent on variations in the Earth’s orbit
What did Milankovitch propose?
summer insolation (solar radiation) at high northern latitudes was critical in melting ice from the previous winter
What feedback was produced by Milankovitch based on his summer insolation theory?
Cooler summers
Less ice melt
Year-on-year build up of ice
Glacial advance
What was the initial focus of the orbital theory?
Explain why periodic glaciations occurred
What criticism was there about the orbital theory?
George Simpson reported large summer and large winter temperature changes, but concluded that these extremes cancelled in the annual average
What 3 things did Milankovitch proposed dominated the amount of solar radiation at earths surface was dominated by?
Eccentricity
Obliquity
Precession
What is the cycle length of eccentricity?
100 and 400 thousand years
