Week 1- DYNAMIC PLANET: The Earth System and Unit Content Flashcards
What are the 5 main spheres of the Earth?
- Atmosphere (gases)
- Cryosphere (ice)
- Hydrosphere (water (liquid))
- Biosphere (sum of all life)
5.Geosphere:
-lithosphere (hard rock) (this can be seen as a sphere in its entirety instead of geosphere in general)
-asthenosphere
-remaining mantle
-outer and inner core
What does the atmosphere consist of?
-this is the gaseous envelope that surrounds the Earth
-includes gases themselves and their chemical composition
-also liquid water droplets/ ice particles that comprise clouds and precipitation
-dust particles
-other aerosol particles suspended in air
What does the cryosphere consist of?
Everything frozen on the Earth’s surface
-polar caps
-glaciers in mountains
-sea ice
- permafrost on soils
What does the hydrosphere consist of?
Includes all the water substance on the Earth in its liquid form
-oceans
-any fresh water: lakes, rivers, groundwater…
What does the lithosphere consist of?
comprises the upper part of the Earth’s surface
maybe down to a few tens of km deep from the Earth’s surface.
It doesn’t include
the deepest parts of the Earth’s mantle
What are climate forcing’s and responses?
cause and effect
external forcings= causes
internal responses= the change that results in the Earth’s climate
What are some examples of external forcings?
plate tectonics
orbital changes
solar input
What is positive feedback?
Positive feedback:
process internal to the Earth’s that acts to enhance the original action
Example: water vapor feedback=
-if Earth’s air temp increases then atmosphere has greater capacity to incorporate water vapour into it, this leads to an increase in evaporation putting more water vapour in air, since this is a greenhouse gas it increases the air temperature.
-So the idea is that the initial increase led to a further increase in air temp hence positive feedback
sometimes positive and negative offset each other
What is negative feedback?
process that counteracts the initial action
Example: cloud feedback
-if we increase the air temperature of the atmosphere it will lead to an increase in evaporation which will put more water vapour in the air so clouds more likely to form leading to more reflection of incoming so less radiation reaches the Earth surface so decrease in atmospheric air temperature
-So the idea is that the initial increase led to a decrease.
sometimes positive and negative offset each other
Where did the ocean and the atmosphere come from?
repeated melting of the Earth led to differentiation of internal structure (crust, mantle, core)
volatiles expelled as volcanic gases
How was the second atmosphere formed? What was its composition?
How= Outgassing produced the second atmosphere
Composition: nitrogen, carbon dioxide, water vapour, ammonia, hydrogen sulphide, sulphur dioxide (that was being emitted from the Earth and volcanoes)
Water vapour cooled by the planet so condenses along with soluble gases (such as sulphur dioxide) to form our first oceans
leaves nitrogen and CO2 dominant
some have argued that nitrogen also arrived by comets, was released by denitrifying bacteria or from the oxidation of ammonia
that nitrogen used more or less its current concentration early in the Life Time
Compare current nitrogen concentration to that of the second atmosphere?
current= 0.79bar (78%)
past= study by Marty et al in 2013 looked at fluid inclusions in hydrothermal courts that had an age of between 3 and a 3.5 billion years ago showed that the isotopic ratios of nitrogen where about the same as we have at present.
-partial pressure was 0.5-1.1 bar
Where did carbon dioxide come from?
today= much carbon stored as organic matter and in limestone (calcium carbonate)
These didn’t exist in early PreCambrian before there was any life
if all carbon in these storehouses was converted to co2 then concentrations would be 100-1000 times present levels in atmosphere (0.04%)
When did O2 appear in atmosphere?
earliest atmosphere would have had no oxygen (21% today)
Oxygen was not outgassed from Earth’s interior unlike other elements
the only abundant source is from photosynthesis
since other planets lack oxygen in their atmosphere it provides evidence that without life we wouldn’t have a lot of oxygen
What is an abiotic source of oxygen on Earth?
UV radiation can photodissociate water vapor
2H2O + UV radiation = 2H2 + O2
Would produce only small amounts (perhaps 10–7 times the present amount).
When did a rapid increase in oxygen concentration occur?
started around 2.5Ga
The Great Oxygenation Event
as more and more oxygen was added to the atmosphere we eventually reached the current value of 21% oxygen that we see today
Why has Earth’s climate been stable?
-A condition for sustained life is that the Earth’s temperature hasn’t fluctuated too wildly.
-Higher CO2 levels during the Proterozoic would mean quite a strong greenhouse effect.
-Then, gradual cooling as CO2 decreased.
-In fact, the Earth seems to have maintained an average temperature of about 15–25°C
-Sun’s brightness has increased by 25–30% during the lifetime of the Earth
-Faint Young Sun Paradox.
To keep temperature within a narrow range, something would have to balance increase in solar radiation.
What is the feedback between Solar Radiation and Removal of Carbon Dioxide?
One estimate: CO2 pressure was as large as 10 atmospheres! (refuted by Marty et al. 2013)
If Sun is stronger, oceans warm.
-Evaporation increases.
-Rainfall increases.
-Continents are weathered more.
-Weathering removes CO2 from the atmosphere.
What are solutions to the Faint Young Sun paradox?
- Feedback between Solar Radiation and Removal of Carbon Dioxide
- Methane as much as 100 parts per million (currently about 1.7 ppm) could have offset the faint sun.
- Lower albedo (less continental area).
- Different models for the evolution of the Sun.
What was the early Archean atmosphere like in summary?
-very little oxygen
-nitrogen concentrations around the same as present
-CO2 and methane could have been higher to offset the Faint Young Sun Paradox
What 2 main gases make up the universe?
helium 36.6%
hydrogen 60.4%
What 2 main gases make up the atmosphere?
Oxygen 21%
nitrogen 78%
What 2 main gases make up the cryosphere and the hydrosphere?
oxygen 86%
hydrogen 11%
