Paleoclimate Records

Question 1

What are the four major hypotheses for the controls on long-term (geologic-scale) climate
change?

Answer 1

1. BLAG Hypothesis
2. Uplift Weathering Hypothesis
3. Organic Carbon Hypothesis
4. Ocean Heat Transport Hypothesis

Question 2

Describe the BLAG Hypothesis

Answer 2

• Involves Sea Floor Spreading
• In areas with higher rates of spreading and higher rates of subduction (more volcanism and so more CO2 in the atmosphere), you get warmer temperatures. When spreading and subduction slows (less volcanism and less CO2), you get cooler temperatures.

Question 3

Who came up with the BLAG hypothesis?

Answer 3

Berner, Lasaga, & Garrels in 1983

Question 4

Describe the Uplift Weathering Hypothesis

Answer 4

• Suck CO2 out of the atmosphere from the weathering of silicate rock

Question 5

Who came up with the idea of Uplift Weathering Hypothesis?

Answer 5

Maureen Raymo & Ruddiman in 1982

Question 6

What happen in the Cenozoic Time Frame that causes uplift of rock to high elevation?

Answer 6

Uplift happens during the Cenozoic is caused by collision (ocean/continent & continent/continent) India to Eurasia creating the Himalayas

Question 7

Provide an analogy for Uplift Weathering Hypothesis

Answer 7

Think about this as the ice cube process – start with a block of ice and want it to melt. Stick it out in FL in August. How to melt this ice faster but at the same temperature? You would break it into smaller pieces.

Question 8

Draw a diagram explaining Uplift Weathering Hypothesis

Answer 8

1. Large mountain glaciers to the high elevations this creates mass wasting.
2. Gravity creates slope precipitation also known as a monsoon.
3. You don’t have this smooth plateau – jagged rough topography that has a lot of surface area and many interspatial sections that allow water and atmosphere gases to chemically weather that rock.
4. Exposure of large volume of crust increases chemical weathering and lowers atmospheric CO2.

Question 9

Uplift Weathering Hypothesis using the Himalayas as an example

Answer 9

• India collides into Eurasia
• Uplift of the Himalayas start to really show at about 35 myr
• Tibetan Plateau is what is being uplifted – large amount of rock available for erosion.
• On top of that, this creates the Indian monsoon. This is where you have winds blowing across the India plateau. This moist humid air moves up and rises as it moves up the Himalayas and then cools, condenses, and rains.
• This creates a lot more chemical weathering during the monsoon.

Question 10

What happens during continent-continent collision

Answer 10

1. Slow down spreading and reduces the amount of vulcanism
2. Creating rugged mass of rock that can be eroded, weathered, and then suck out CO2

Question 11

The Ganges delta is not only the biggest sediment sink but also…

Answer 11

largest sink for organic carbon

Question 12

Who developed the Organic Carbon Burial Hypothesis?

Answer 12

• France-Lanord & Derry – Galy

Question 13

The Ganges and Bengal Fan is responsible for what percent of burial of terrestrial organic carbon?

Answer 13

20%

Question 14

The Ocean Heat Transport Hypothesis

Answer 14

• Changes in ocean circulation due to changes in continental positions-> opening & closing oceanic gateways
  
  • That ocean circulation controls the transfer of heat from the tropics to the polls

Question 15

• Key things have happened during the Cenozoic timeframe (65 Myr) that have something to do with the Ocean Heat Transport Hypothesis

Answer 15

• Southern Ocean – Australia was connected to Antarctica
• Antarctica and South America were connected to each other.
  
  • 33,26 Myr ago – opening of Tasmanian-Antarctica gateway
  • 25-20 Myr – opening of Drake passage (South America & Antarctica) -> This allows for the Southern Ocean we know today and allows for Southern Ocean circulation.
  • Clockwise rotation around antarctica – this stops the transfer of heat.

Question 16

Using the Ocean Heat Transport Hypothesis, describe the transfer of a warm water molecule

Answer 16

• A warm water molecule travels south from the equator.
• Gets trapped in the circulation around Antarctica and never actually reaches Antarctica. As a result, Antarctica never receives the heat and allows it to form ice.

Question 17

What is the albedo effect?

Answer 17

Dark water absorbs light – ice reflects the sunlight (albedo effects)

Question 18

What is Eccentricity and draw a diagram?

Answer 18

• How circular versus elliptical is the Earth’s orbit around the sun
• Periodicity: 96,000 yrs

Question 19

What are the three Milankovitch Cycles?

Answer 19

1. Eccentricity
2. Precession
3. Obliquity

Question 20

What is Precession and draw a diagram?

Answer 20

Circular precession of axis of rotation

• Periodicity: 23,000 years

Question 21

What is Obliquity and draw a diagram

Answer 21

Amount of tilt of the earths axis: affects seasonality

Periodicity:41,000 yrs

Question 22

What process allows the table to be set by Cenozoic climate cooling to throw us in periods of warm and cold temperatures?

Answer 22

Milankovitch

Question 23

What allows us to understand the impact of the Milankovitch Cycles?

Answer 23

It is the marine sedimentary records, benthic forams, delta 0 18 proxies and goes geochronology Uranium/Thorium and main sedimentary record of that allow us to understand the impact of Milankovitch Cycles on earth’s climate (large cooling events recorded in sea floor sediments).