Lecture 3- Milankovitch cycles etc.

Question 1

Sapropels

Answer 1

Organic rich black muds- layers of high carbon concentrations

Question 2

Sapropels- low salinity lids

Answer 2

Prevent oxygen rich water being formed as low salinity fresh water sits on the surface

Question 3

Sapropels and precession

Answer 3

Sapropels sit on precession spikes (strong indication insolation and rainfall at source of the Nile)

Question 4

Urbain Leverrier

Answer 4

Applied Newton’s gravitational laws to orbits/masses of planets

Question 5

Eccentricity change- 100,000 years

Answer 5

1-6%

Question 6

Obliquity change (tilt)- 41,000 years

Answer 6

24.5 to 22.1 degrees

Question 7

When tilt is decreased…

Answer 7

Polar regions receive less sunlight

Question 8

When tilt is increased…

Answer 8

Polar regions receive more sunlight…

Question 9

Precession of the equinoxes

Answer 9

Caused by the ‘wobble’ of the earth’s axis

Question 10

Cause of decrease in summer radiaion

Answer 10

Caused by a decrease in axial tilt

Question 11

Tilt cycle (41,000)

Answer 11

Predominates at poles, gets smaller at equator

Question 12

Precession (22,000)

Answer 12

Is small at poles, larger at equator

Question 13

Eccentricity cycle (100,000)

Answer 13

Amount of energy change involved in the eccentricity
cycle is small

Question 14

Problem with dating glaciers

Answer 14

Morraine of previous glaciers are bulldozed- only evidence of the most recent glacier

Question 15

Carbonate ooze (depth)

Answer 15

<4000m

Question 16

2 types of info found from carbonate ooze:

Answer 16

1. Species distribution of foraminifera reflects temperature and
   nutrients
2. Shells lock isotopic (C & O) concentrations from water
   of formation

Question 17

Carbonate compensation depth

Answer 17

More carbonate can be dissolved in Atlantic ocean as CCD is deeper

Question 18

Why is CCD deeper in Atlantic

Answer 18

Organic matter rains down and oxidised carbonates move down the water column and make the water more acidic

Question 19

Atlantic cores

Answer 19

Faster sedimentation: more resolution

Question 20

Assumptions made when tuning

Answer 20

• An orbital signal is present
• Time lag
• Which component of orbital change the
  record responds to
• Continuous and complete record

Question 21

Issues with using magnetic susceptibility for global changes

Answer 21

Only useful for regional changes

Question 22

The further you go back in time

Answer 22

The more difficult it is to use ice sheet models as your main measure