location of large igneous provinces:

Location of Large Igneous Provinces:

Why Cretaceous oil is important….

Heat is pumped in the atmosphere – from the hot equatorial regions to the poles.

And it works the same way in ocean circulation, although the continents require a more complicated path.

Heat transfer through deep ocean today;

Formation of cold dense water in polar regions with some warm saline water from Mediterranean

Deep ocean 100 My ago was filled with warm saline bottom water;Cretaceous bottom water formed in tropics or subtropics and flowed pole-ward transferring heat

Warm saline water could have formed in Northern hemisphere when salinity exceeded 37%.

The point of this…

Ocean circulation – plays a very important role in determining global climate.

Ocean circulation has not always been like is it today.

In the Cretaceous – it operated essentially ‘in reverse’ -

I.e., it was salinity-driven (not temperature) and almost all bottom water was formed near the equator.

And the Oceans went ‘anoxic’ for millions of years….

End of an Era – the end-Cretaceous ‘event’

Asteroid impacts can have apocalyptic consequences, but – the impact is not usually long-term.

Except in the Eocene…..

Weathering of rock: CO2 + XSiO3= XCO3+SiO2

Oceanic crust

Weathered sediment from continents

Ocean

Burial of organics: CO2 + H2O = CH2O+O2

Weathering of organics: CH2O+O2 = CO2 + H2O

Metamorphism of rock;

XCO3+SiO2=CO2 +XSiO3

Why is Plate Tectonics this important to CLIMATE? Long term (>105 year) concentrations of atmospheric CO2, O2, CH4 are set by many different interactions, including plate tectonics.

Fast seafloor spreading – high CO2

input: both at mid-ocean ridges (new CO2) and at subduction zones (re-cycled

CO2). Slow SFS, low CO2.

And this variation in CO2 input has both positive and negative feedbacks.

BOTH examples => are negative feedback

THE 'BLAG' HYPOTHESIS - WHAT IS IT?

LARGE-SCALE CLIMATE CHANGES ARE CONTROLLED BY THE AMOUNT OF CO2 IN THE ATMOSPHERE (the thermostat),

AND ATMOSPHERE CO2 CONTENT IS, IN TURN, CONTROLLED BY THE PROCESS OF PLATE TECTONICS, i.e., • seafloor spreading rates,

• rates of subduction, • mountain-building and weathering.

• sea level changes

Tracing the pathway of CO2.

(1) MOR eruptions: (2) transfer to atmosphere: (3) combined chemically during weathering: (4) transfer to ocean via rivers: (5) incorporated in biology

(6) Eventually sinks to seafloor as sediment: (7) seafloor is subducted: (8) mantle heat released CO2 in subduction zone: (9)

emitted by subduction volcanoes back into atmosphere.

Then, the cycle starts over.

Fast seafloor spreading – high CO2

input: both at mid-ocean ridges (new CO2) and at subduction zones (re-cycled

CO2). Slow SFS, low CO2.

And this variation in CO2 input has both positive and negative feedbacks.

BOTH examples => are negative feedback

Weathering – the only real method for getting rid of CO2 (i.e., carbon) from the atmosphere.

And even then, some of it sneaks back into the air…

2. The acidic rain formed by the

combination of CO2 and H2O in clouds rains

to the ground and reacts with limestones.

CaCO3 + H+ + HCO3- --> Ca++ + 2HCO3

-

1.In clouds, carbon dioxide reacts with water to form a weak acid.

H2O + CO2 --> H2CO3

H2CO3 <=> H+ + HCO3-

3. The acidic rain formed by the combination of CO2 and H2O in clouds falls to the

ground and reacts with minerals in continental rocks.

2NaAlSi3O8 + 2H+ + 2HCO3- + 9H2O --> Al2Si2O5(OH)4 + 2Na+ + 2HCO3

- + 4H4SiO4

(feldspars) (clays) (silicic acid)

4. The dissolved ions in sea water leave it in a variety of ways:

i.e., organisms building shells

Ca++ + 2HCO3- --> CaCO

3 + H2O + CO2 (forams) and

H4SiO4 --> SiO2·2H2O (diatoms)

5. Ocean sediments consist of biogenically produced shells that rain to the ocean floor and clay minerals and quartz, the insoluble products of erosion. The latter are washed to the sea by rivers or carried to the ocean by winds from arid continental areas.

7. Clay minerals and limestones are heated at subduction zones and react with SiO2

SiO2 + CaCO3 --> CaSiO3 + CO2

8. Volcanoes above subduction zones produce CO2, H2O, H2S, and SO2.

And some CO2 gets back into the atmosphere.

But SOME is carried down into the mantle – and buried.

The uplifted Tibetan plateau also creates it’s ‘own weather’ – the Monsoons.

The summer sun on the plateau causes an upwelling zone over the plateau, which draws (warm, very moist) air from the continental margins.

This causes very heavy seasonal rains, which are effective in weathering of the rocks and flushing nutrients into the surrounding ocean.

Weathering rates depend on

temperature, elevation, rain, vegetation cover

The flux of sediments from the Tibetan plateau has increased dramatically over the last 40 My (by factor of 10).

This both pulls CO2 directly from the atmosphere (as carbonic acid) but also fertilizes the upper ocean and increases the ‘biological pump’.

Possible problem with this hypothesis: there are negative feed-backs on weathering as a control on global climate.

Increasing weathering in high plateaus can cause a DECREASE in weathering in areas that are NOT high plateaus.