Long term climate regulation Flashcards
For every two moles of carbon that is taken from the atmosphere in silicate weathering…
One mole of carbon is released again to the atmosphere in carbonate precipitation. And another is eventually released many many years later by volcanism.
How many recorded glaciations have been on Earth? Try and Name them.
6 Glaciations.
-Mid Archaen
-Huronian
-Neo-protozoic
-Late ordovician
-Permo-carboniferous
-Quatenary
A long term cold period is called a ______. Short term cold periods within this period are called ______ periods. Short term warm periods are called ________ periods.
Glaciation. Glacial period. Interglacial Period.
A Long term warming period is called a _________
Greenhouse period.
What are physical evidence examples of Cold periods
Tillites, Glacial Striations, Dropstones, Banded Iron, Cap Carbonates.
Main suspects of climate change regulations and forcings?
Enhanced Greenhouse Effect, Carbonate Geochemical cycle, Self destructive life.
Describe how Silicate weathering plays a role in climate regulation and what is it dependent on.
Silicate weathering (draws down carbon) is heavily dependent on Temperature and precipitation. A higher availability of weather-able material on the surface of the earth means more silicate weathering. The position of the continents determines their susceptibility to weathering conditions, and the sea level determines how much material is exposed to these conditions.
What is the relationship between the position of continents and the Carbonate geochemical cycle?
When continents are closer to the equator, they are exposed to higher temperatures and precipitation. This increases silicate weathering and therefor the drawdown of CO2 from the atmosphere.
What is the relationship between sea level and the carbonate geochemical cycle?
When sea level decreases, more material is exposed to geochemical weathering, increasing silicate weathering, increasing the drawdown of Co2 from the atmosphere. When sea level rises, less material is exposed to silicate weathering so less co2 is drawn down from the atmosphere.
Explain the Faint Young Sun Paradox
Nuclear fusion helps us understand that the sun gets hotter over time. 4.6BYA on a younger earth mean there was a younger sun, with 30% less luminosity then now. This difference in solar energy being received by the earth would have shown a frozen planet even 3.7 BYA. But 3.7BYA there was life and liquid water, meaning other factors had to be at play.
Theoretical Solution to the Faint Young Sun Paradox
Earth consisted of a stable equilibrium on the basis of methane production and organic methane haze. Higher temperature: more methane production by methanogens.below optimum: more CH4 → stronger greenhouse effect
above optimum: more CH4 → more organic haze (absorption of incoming radiation and re-emission into space)
Explain the Great Oxidation Event.
2.46 BYA, photosynthesizers raise oxygen levels after 200 million years of existing, this is because earth had a certain amount of oxygen sinks that needed to be filled. Cyanobacteria only developed the ability to fixate Nitrogen (a limiting factor in the production of oxygen) 2.5MYA. The combination of these two reasons (ox sinks and cyanobacteria nitrogen fixation) ultimately caused oxygen to increase.
What do banded iron formations show us?
When there is little to no oxygen in the atmosphere there was a high concentration of soluble ferrous iron. The appearance of oxygen during the great oxidation event created insoluble ferrous iron that settles on the sea floor.
How was the Huronian Glaciation Kickstarted?
Due to the great oxidation event, oxygen oxidised methane, weakening the greenhouse effect and the organic haze that coated the earth, kickstarting a glaciation.
How did the earth save itself from the Huronian glaciation
carbonate-silicate geochemical cycle to the rescue!
-growth of icecapes and decline in temperature slow down silicate weathering ( less precipitation, less exposed material)
-volcanism continues
-greenhouse strengthens again as a result
How was the Neo-protozoic glaciation kickstarted?
A significant fraction of the planets continents were located in the tropic. This mean that a significant amount of material was exposed to an area of high temperature and high precipitation, increase in CO2 draw down from the atmosphere as a result of Silicate Weathering.
- at high altitudes: continents are covered in ice sheets -> decrease in silicate weathering.
-at low altitudes material is weathered–> incerease in silicate weathering, this boosts ice coverage which at a tipping point boosts the ice albedo feedback loop to the point of a snowball earth.
How did the earth escape the Neo-protozoic glaciation?
Carbonate-silicate geochemcial cycle to the rescue!
-ice sheets cover weatherable material and lower temperatures decrease precipitation, stopping draw down of co2 from the atmosphere.
-at the same time, volcanism continues to release co2 into the atmosphere, and after a long time, greenhouse effect is strengthened once again.
How did the permocarboniferous glaciation start?
Land plants pull Co2 out of the atmosphere and store it in the ground, releasing oxygen as a result of photosynthesis. Roots help weather terrain and increase vulnerability of material to silicate weathering.
How did the permo-carboniferous period end?
Mesozoic warm period: increase rate of seafloor spreading means more volcanism. Higher sea level as a result means less silicate weathering.
How did the mesozoic warm period come to an end?
kickstart of the quaternary glaciation as a result of the crash of the indian subcontinent into the eurasian continent. Tectonic uplift alongside enormous amounts of monsoon driven silicate weathering led to the next glaciation.
