Cycles

Question 1

What is dendrochronology?

Answer 1

the study of tree rings to date past events and areas

Question 2

What do tree rings represent?

Answer 2

Annual growth/ seasons/ growth conditions

Question 3

How ill tree rings reflect the seasons?

Answer 3

Less dense in summer due to better growth conditions
Dense in winter with worse conditions

Question 4

How long can trees be used to date?

Answer 4

~14,000 years

Question 5

What do ice cores record?

Answer 5

CO2 and temperature

Question 6

What is the length of glacial seasons?

Answer 6

~100,000 years

Question 7

What was the climate 20,000 years ago in europe?

Answer 7

Glacial

Question 8

How do ice cores represent time?

Answer 8

Will creating banding of snow layers which trap gas bubbles of that atmosphere at that time

Question 9

How far back can ice cores be used to date?

Answer 9

~1 million years

Question 10

What can be seen with in the Mediterranean rock record which shows cycles?

Answer 10

Prominent rhythmic alterations in rock type in marine and lake sediments

Question 11

What does the presence of high frequency switches of sediment colour and bundling show?

Answer 11

Multiple cycles occurring at once

Question 12

Why are lakes and river sediments less likely to show signs of cycles?

Answer 12

Lakes affected by uplift and tectonics
Rivers are highly dynamic

Question 13

What other type of core can cycles be seen in?

Answer 13

Marine cores

Question 14

What did Luis Agassiz propose?

Answer 14

extinction of the Pleistocene megafauna was due to widespread and deep “winter”

Question 15

What gave evidence in glacial environments that glaciers had once been larger?

Answer 15

Erratic’s and moraines being seen at higher elevations

Question 16

What did the realisation of greater glacial extent provide a new explanation for?

Answer 16

Erratic’s and other glacial features across N. Europe and N. America

Question 17

Who was Milutin Milankovitch?

Answer 17

A Serbian engineer and meteorologist who worked on a mathematical theory of climate

Question 18

What did Milankovitch calculate?

Answer 18

Seasonal variations in the amount of solar radiation received by the Earth were dependent on variations in the Earth’s orbit

Question 19

What did Milankovitch propose?

Answer 19

summer insolation (solar radiation) at high northern latitudes was critical in melting ice from the previous winter

Question 20

What feedback was produced by Milankovitch based on his summer insolation theory?

Answer 20

Cooler summers
Less ice melt
Year-on-year build up of ice
Glacial advance

Question 21

What was the initial focus of the orbital theory?

Answer 21

Explain why periodic glaciations occurred

Question 22

What criticism was there about the orbital theory?

Answer 22

George Simpson reported large summer and large winter temperature changes, but concluded that these extremes cancelled in the annual average

Question 23

What 3 things did Milankovitch proposed dominated the amount of solar radiation at earths surface was dominated by?

Answer 23

Eccentricity
Obliquity
Precession

Question 24

What is the cycle length of eccentricity?

Answer 24

100 and 400 thousand years

Question 25

What is the cycle length of obliquity?

Answer 25

41,000 years

Question 26

What is the cycle length of precession?

Answer 26

23,000 years

Question 27

What marine records show that proves Milankovitch’s theory?

Answer 27

Marine records show glacial and interglacial cycles which show his cycle periods

Question 28

What are Earths orbital variations caused by?

Answer 28

Mutual gravitational interactions between the sun, planets and satellites

Question 29

What can be done to see how the orbital cycles would have been affected in the past?(Laskar solutions)

Answer 29

Can be back calculated using supercomputer to show relative positions of planets in the past useful to around 55 Mya

Question 30

What is the range for obliquity?

Answer 30

21.5 to 24.5

Question 31

What are perihelion and apehelion?

Answer 31

Perihelion point on earths orbit closest to the sun
Apehelion point of earths rotation furthest from the sun

Question 32

What are the relative distances of perihelion and apehelion?

Answer 32

A = 158 million km
P = 153 million km

Question 33

What is an equinox?

Answer 33

Point where day and night are equal

Question 34

How many equinoxes are there?

Answer 34

2 (~20 March / 22 September)

Question 35

What are the solstices?

Answer 35

When sun appears to reach highest (summer) / lowest (winter) point (& longest / shortest days)

Question 36

What does eccentricity relate to?

Answer 36

The shape of earths orbit being roughly elliptical

Question 37

When is the NH closest to the sun?

Answer 37

In winter (milder winter)

Question 38

What does low eccentricity cause?

Answer 38

More variability in seasonal cycles

Question 39

What does obliquity relate to?

Answer 39

The tilt of earths axis

Question 40

What does a tilted axis give earth?

Answer 40

Seasons as no tilt there would be equal conditions or 90* tilt = extreme seasons)

Question 41

What is precession?

Answer 41

The wobble of earth on its axis

Question 42

What can precession alter?

Answer 42

The position of perihelion

Question 43

What are the complex dynamics of identifying orbital variation?

Answer 43

They act in unison to determine insolation and seasonality

Question 44

How can oscillation’s be presented in the frequency domain? (with example)

Answer 44

As spectra as 1/Period (frequency) so 20,000 yrs = 0.00005 years

Question 45

What will a perfect oscillation of orbital data be like?

Answer 45

infinite duration will give a spectrum peak that
is infinitely narrow at the central frequency

Question 46

How will signals with a finite strength be presented?

Answer 46

Smeared out spectrum

Question 47

What does power relate to with orbital cycles in data?

Answer 47

coherence and strength of cycles at given frequency