6.4 - Weathering And Soil

Question 1

What is the biogeochemical cycle?

Answer 1

The biogeochemical cycle, is the process by which nutrients and other elements move through ecosystems and are recycled over time. There are several major biochemical cycles that play a crucial role in supporting life on Earth, including the carbon cycle, nitrogen cycle, phosphorus cycle, and water cycle.

Each of these cycles involves the movement of elements or compounds through various environmental compartments, such as the atmosphere, hydrosphere, lithosphere, and biosphere. For example, the carbon cycle involves the movement of carbon dioxide (CO2) from the atmosphere into plants through photosynthesis, where it is converted into organic matter. This organic matter is then consumed by other organisms, releasing CO2 back into the atmosphere through respiration and decomposition.

Similarly, the nitrogen cycle involves the movement of nitrogen through the atmosphere, soil, and living organisms. Nitrogen is taken up by plants in the form of nitrate or ammonium ions, which are then consumed by animals. Nitrogen is also fixed by certain bacteria in the soil, which convert it into a form that can be used by plants. Eventually, nitrogen is returned to the soil through decomposition and excretion, where it can be taken up again by plants.

The phosphorus cycle involves the movement of phosphorus through soil, water, and living organisms. Phosphorus is taken up by plants in the form of phosphate ions, which are then consumed by animals. Phosphorus is also released into the environment through weathering of rocks and minerals, and is eventually returned to the soil through decomposition and excretion.

Overall, the biochemical cycles are crucial for maintaining the balance of nutrients and elements in ecosystems, and are essential for supporting life on Earth. Any disruption to these cycles, such as through pollution or deforestation, can have significant impacts on the health and functioning of ecosystems.

Question 2

Inorganic carbon cycle in depth

Answer 2

The inorganic carbon cycle is a process that involves the movement of carbon in its inorganic forms through various reservoirs on Earth. Inorganic carbon refers to carbon that is not part of organic matter, but instead exists as carbon dioxide (CO2), bicarbonate (HCO3-), and carbonate (CO32-) ions.

The inorganic carbon cycle is closely linked to the Earth’s atmosphere and oceans, and plays an important role in regulating the planet’s climate. Here are the main steps of the inorganic carbon cycle:

Atmospheric CO2: Carbon dioxide is a gas that is present in the Earth’s atmosphere. It is primarily released into the atmosphere through volcanic activity, respiration of organisms, and the burning of fossil fuels.

Ocean uptake: A large portion of atmospheric CO2 dissolves into the ocean, where it reacts with seawater to form bicarbonate and carbonate ions. This process, called ocean uptake, helps to regulate the concentration of CO2 in the atmosphere.

Carbonate deposition: Some of the bicarbonate and carbonate ions in the ocean react with calcium ions to form calcium carbonate (CaCO3), which can accumulate and form sedimentary rocks over time.

Carbon release: Over geologic time, carbon can be released back into the atmosphere through volcanic activity, weathering of rocks, and oceanic circulation.

The inorganic carbon cycle is important for regulating the pH of the ocean, as well as the concentration of CO2 in the atmosphere. The uptake of CO2 by the ocean helps to reduce the amount of CO2 in the atmosphere, while the deposition of carbonate minerals helps to remove carbon from the ocean. However, human activities such as the burning of fossil fuels have caused a rapid increase in atmospheric CO2 levels, which has led to changes in the climate and ocean acidification.

Question 3

Inorganic carbon cycle overview:

Answer 3

• Timescales of instantaneous (diffusion and equilibrium) to 100’s to 1 million years
• Chemical, biological, and geological processes (instantaneous -> daily -> Ma)
• Stabalized by climate feedbacks over geologic timescales

Question 4

What is important about the reservoir sizes of carbon and the transfer between them?

Answer 4

It gives an understanding of the big picture of how carbon (or other elements) cycle through our planet (and potentially others)

Processes to consider depend on the timescale of interest

Question 5

What are the reservoirs of inorganic/oxidised carbon near earths surface?

Answer 5

Limestone in sedimentary rocks = 40,000,000 Gt C

HCO3- in the oceans = 37,000 Gt C

Marine carbonate sediments = 2500 Gt C

CO3 2- in the oceans = 1300 Gt C

Atmospheric CO2 = 760 Gt C

CO2 (aq) in the oceans = 740 Gt C

Question 6

Inorganic medium-term carbon cycle with fluxes

Answer 6

The inorganic medium term carbon cycle is a process that involves the movement of carbon in its inorganic forms through various reservoirs on Earth over a period of several thousand years. Here are the main steps of the inorganic medium term carbon cycle, along with the fluxes that occur between the different reservoirs:

Atmosphere: Carbon dioxide (CO2) is present in the Earth’s atmosphere as a gas. The concentration of CO2 in the atmosphere is influenced by several processes, including the burning of fossil fuels, volcanic activity, and the respiration of organisms.

Ocean uptake: A significant amount of atmospheric CO2 is taken up by the oceans, where it reacts with seawater to form bicarbonate (HCO3-) and carbonate (CO32-) ions. This process, called ocean uptake, helps to regulate the concentration of CO2 in the atmosphere.

Sedimentary rocks: Some of the bicarbonate and carbonate ions in the ocean react with calcium ions to form calcium carbonate (CaCO3), which can accumulate and form sedimentary rocks over time. This process, called carbonate deposition, helps to remove carbon from the ocean.

Weathering: Over time, sedimentary rocks can be weathered and release CO2 back into the atmosphere. This process, called weathering, helps to regulate the concentration of CO2 in the atmosphere.

Volcanic activity: Carbon can also be released into the atmosphere through volcanic activity. Volcanic eruptions can release large amounts of CO2 into the atmosphere, contributing to changes in the Earth’s climate.

The inorganic medium term carbon cycle is important for regulating the concentration of CO2 in the atmosphere and influencing the Earth’s climate over a period of thousands of years. However, human activities such as the burning of fossil fuels have caused a rapid increase in atmospheric CO2 levels, which is leading to changes in the Earth’s climate and ocean acidification.

Question 7

Inorganic long term carbon cycle

Answer 7

The inorganic medium term carbon cycle is a process that involves the movement of carbon in its inorganic forms through various reservoirs on Earth over a period of several thousand years. Here are the main steps of the inorganic medium term carbon cycle, along with the fluxes that occur between the different reservoirs:

Atmosphere: Carbon dioxide (CO2) is present in the Earth’s atmosphere as a gas. The concentration of CO2 in the atmosphere is influenced by several processes, including the burning of fossil fuels, volcanic activity, and the respiration of organisms.

Ocean uptake: A significant amount of atmospheric CO2 is taken up by the oceans, where it reacts with seawater to form bicarbonate (HCO3-) and carbonate (CO32-) ions. This process, called ocean uptake, helps to regulate the concentration of CO2 in the atmosphere.

Sedimentary rocks: Some of the bicarbonate and carbonate ions in the ocean react with calcium ions to form calcium carbonate (CaCO3), which can accumulate and form sedimentary rocks over time. This process, called carbonate deposition, helps to remove carbon from the ocean.

Weathering: Over time, sedimentary rocks can be weathered and release CO2 back into the atmosphere. This process, called weathering, helps to regulate the concentration of CO2 in the atmosphere.

Volcanic activity: Carbon can also be released into the atmosphere through volcanic activity. Volcanic eruptions can release large amounts of CO2 into the atmosphere, contributing to changes in the Earth’s climate.

The inorganic medium term carbon cycle is important for regulating the concentration of CO2 in the atmosphere and influencing the Earth’s climate over a period of thousands of years. However, human activities such as the burning of fossil fuels have caused a rapid increase in atmospheric CO2 levels, which is leading to changes in the Earth’s climate and ocean acidification.

Question 8

Why is it useful to understand reservoir fluxes and sizes

Answer 8

It helps to understand roughly how long it takes a process to change a reservoir size

Eg. Total carbon in the ocean and atmosphere = 42300 Gt

Flux of CO2 removal by Si weathering = 0.03 Gt/yr

Residence time of carbon against removal by silicate weathering
= 42300 Gt / 0.03 Gt/yr - 1.5x10(6) yr

Question 9

How is C02 removed from the atmosphere?

Answer 9

Weathering silicates remove the CO2 from the atmosphere

Question 10

How does carbonic acid cause chemical weathering?

Answer 10

CO2 dissolves in rainwater, forms carbonic acid and dissociates

CO2 + H2O <—-> H+ + HCO3-

Rocks exposed at earths surface undergo chemical attack from this dilute acid

Chemical weathering by carbonic acid primarily affects two prominent classes of minerals - carbonates and silicates

Question 11

Carbonate vs silicate weathering

Answer 11

Carbonate weathering and silicate weathering are two types of weathering processes that play important roles in the inorganic carbon cycle.

Carbonate weathering involves the breakdown of calcium carbonate (CaCO3) rocks, such as limestone and chalk, through exposure to rainwater and carbon dioxide (CO2) in the atmosphere. This process releases calcium ions (Ca2+) and bicarbonate ions (HCO3-) into rivers and oceans. These ions can then react with other elements to form sedimentary rocks, shells, and other marine life. Carbonate weathering helps to regulate the concentration of CO2 in the atmosphere by removing it through chemical reactions with rocks, which ultimately results in its transfer to the ocean.

Silicate weathering, on the other hand, involves the breakdown of silicate rocks, such as granite and basalt, through exposure to water and carbon dioxide in the atmosphere. This process releases silica (SiO2) and other ions such as calcium (Ca2+) and magnesium (Mg2+) into rivers and oceans. Silicate weathering plays a critical role in the long-term regulation of atmospheric CO2 levels, as it consumes CO2 through a chemical reaction between the silicate minerals and atmospheric CO2. This process also contributes to the formation of sedimentary rocks and the production of nutrients that can support plant growth.

In summary, both carbonate weathering and silicate weathering are important processes in the inorganic carbon cycle. Carbonate weathering helps to remove CO2 from the atmosphere through chemical reactions with calcium carbonate rocks, while silicate weathering helps to consume atmospheric CO2 through chemical reactions with silicate rocks.

Question 12

Carbonate vs silicate weathering equations

Answer 12

Carbonate weathering:

CaCO3 + H2CO3 —-> Ca2+ + 2HCO3-

Silicate weathering:

CaSiO3 + 2H2CO3 —> Ca2+ + 2HCO3- + SiO2 + H2O

Much of this Ca and SiO2 re-precipitates in place in soils, but depending on relief, effective precipitation, etc. also winds up in rivers and transported to the oceans.

Question 13

What is biomineralization

Answer 13

Biomineralisation is the process by which organisms create hard structures within their bodies, typically composed of minerals such as calcium carbonate (CaCO3) or silica (SiO2). In the oceans, biomineralisation is an important process that plays a critical role in the carbon cycle and the formation of marine ecosystems.

Marine organisms that are involved in biomineralisation include corals, mollusks, foraminifera, and coccolithophores, among others. These organisms secrete hard structures, such as shells or skeletons, that are made up of various forms of calcium carbonate or silica. The process of biomineralisation involves the precipitation of these minerals from seawater, which can be facilitated by the organism’s metabolism, pH changes, or the secretion of organic compounds.

The formation of calcium carbonate structures through biomineralisation has significant implications for the global carbon cycle. Calcium carbonate is a form of inorganic carbon, and the production of these structures by marine organisms can result in the removal of carbon dioxide (CO2) from seawater. When these structures are buried in sediment, they can contribute to the long-term storage of carbon. Additionally, the formation of these structures provides habitat for many other marine organisms, which can contribute to the formation of complex marine ecosystems.

However, ocean acidification, which is caused by the absorption of excess CO2 from the atmosphere, can negatively impact biomineralisation in the oceans. As the pH of seawater decreases, the availability of carbonate ions in seawater decreases, which can make it more difficult for marine organisms to form calcium carbonate structures. This can have significant impacts on marine ecosystems and the global carbon cycle.

Question 14

What is the net effect of carbonate weathering and precipitation reactions?

Answer 14

Carbonate weathering and precipitation has no net effect on Carbon

Question 15

What is biomineralisation?

Answer 15

Biomineralisation is the process by which organisms create hard structures within their bodies, typically composed of minerals such as calcium carbonate (CaCO3) or silica (SiO2). In the oceans, biomineralisation is an important process that plays a critical role in the carbon cycle and the formation of marine ecosystems.

Marine organisms that are involved in biomineralisation include corals, mollusks, foraminifera, and coccolithophores, among others. These organisms secrete hard structures, such as shells or skeletons, that are made up of various forms of calcium carbonate or silica. The process of biomineralisation involves the precipitation of these minerals from seawater, which can be facilitated by the organism’s metabolism, pH changes, or the secretion of organic compounds.

The formation of calcium carbonate structures through biomineralisation has significant implications for the global carbon cycle. Calcium carbonate is a form of inorganic carbon, and the production of these structures by marine organisms can result in the removal of carbon dioxide (CO2) from seawater. When these structures are buried in sediment, they can contribute to the long-term storage of carbon. Additionally, the formation of these structures provides habitat for many other marine organisms, which can contribute to the formation of complex marine ecosystems.

However, ocean acidification, which is caused by the absorption of excess CO2 from the atmosphere, can negatively impact biomineralisation in the oceans. As the pH of seawater decreases, the availability of carbonate ions in seawater decreases, which can make it more difficult for marine organisms to form calcium carbonate structures. This can have significant impacts on marine ecosystems and the global carbon cycle.

Question 16

What is the net effect of carbonate weathering and precipitation reactions?

Answer 16

The net effect of carbonate weathering and precipitation reactions is the removal of carbon dioxide (CO2) from the atmosphere, which helps to regulate the Earth’s climate over long timescales.

Carbonate weathering involves the breakdown of calcium carbonate (CaCO3) rocks through exposure to rainwater and CO2 in the atmosphere. This process releases calcium ions (Ca2+) and bicarbonate ions (HCO3-) into rivers and oceans. The bicarbonate ions can react with calcium ions and other elements in seawater to form solid calcium carbonate, which can be deposited as sediment on the ocean floor. This process, known as precipitation, removes bicarbonate ions from seawater, effectively removing CO2 from the system.

The net effect of carbonate weathering and precipitation reactions is the removal of CO2 from the atmosphere, which is transferred to the ocean as dissolved inorganic carbon (DIC). This process is one of the key mechanisms by which carbon is cycled between the atmosphere, oceans, and land. Over long timescales, the removal of CO2 through carbonate weathering and precipitation reactions can help to regulate the Earth’s climate by reducing the greenhouse effect caused by excess CO2 in the atmosphere.

It is worth noting that the net effect of carbonate weathering and precipitation reactions can be influenced by a variety of factors, such as temperature, rainfall, and the type of rocks present in a given region. Additionally, changes in ocean chemistry, such as ocean acidification, can impact the rate and efficiency of these processes.

Question 17

What is the net effect of silicate weathering and biomineralisation

Answer 17

CaSiO3 + CO2 —-> CaCO3 + SiO2

• A net conversion of atmospheric CO2 to solid CaCO3
• Much of this biogenic carbonate will re-dissolve, but there is small amount that forms carbonate structures (like the cliffs of Dover) which requires a return flux of CO2 to the atmosphere from the sediments

This can be from tectonics eg. Volcanoes

Question 18

What it carbonate metamorphism?

Answer 18

CaCO3 + SiO2 —> CaSiO3 + CO2

Carbonate metamorphism reverses the net effect of silicate weathering and carbonate precipitation.

Carbonate metamorphism refers to the process of transforming carbonate rocks (such as limestone, dolomite, or marble) under conditions of high temperature and pressure. This process typically occurs during mountain building events or in areas of the Earth’s crust where tectonic forces are actively deforming rocks.

Under high temperatures and pressures, the minerals in carbonate rocks can undergo a series of chemical and physical changes. For example, the minerals in limestone can be transformed into marble through recrystallization, which involves the dissolution and re-precipitation of mineral grains. Similarly, dolomite rocks can be transformed into magnesium-rich marbles through the replacement of calcium ions by magnesium ions.

The specific conditions required for carbonate metamorphism depend on a variety of factors, such as the type of rock, the depth and temperature of burial, and the duration of exposure to high pressures and temperatures. For example, the transformation of limestone into marble typically requires temperatures above 400°C and pressures of several kilobars, while the transformation of dolomite requires even higher temperatures and pressures.

Carbonate metamorphism can have important implications for the mineral resources and geological history of a region. For example, marble is a valuable building material that has been used in construction for thousands of years. Additionally, the presence of metamorphosed carbonate rocks can provide clues about the geologic history of a region, including past tectonic activity and changes in the Earth’s climate.

Question 19

What does Carbon input from volcanism and tectonics cause?

Answer 19

Carbonate metamorphism

Question 20

What is the long term effect of volcanism and tectonics?

Answer 20

Weathering silicates remove atmospheric CO2

Question 21

The carbonate-silicate cycle negative feedbacks

Answer 21

Silicate weathering = This POSITIVE feedback occurs when the rate of silicate weathering is increased, leading to greater amounts of CO2 being removed from the atmosphere through the formation of carbonates. As CO2 levels decrease, the greenhouse effect is weakened, which leads to cooler temperatures and reduced rates of silicate weathering which is a NEGATIVE FEEDBACK.

Surface temperature = This feedback occurs when changes in the Earth’s temperature alter the rate of weathering and the balance between carbonate and silicate deposition. For example, warmer temperatures can increase the rate of chemical weathering, which can accelerate the removal of CO2 from the atmosphere and lead to cooler temperatures over time. Can also increase rainfall which increases weathering and draw down of C02 (NEGATIVE FEEDBACK)

Rainfall = Increased temperatures cause increased rainfall. As well, Increased rates of silicate weathering can lead to a positive feedback loop in which the formation of soils leads to increased vegetation cover, which leads to increased rainfall, which in turn enhances silicate weathering.

Question 22

Future timescale predictions for fossil fuel co2

Answer 22

The timescale for CO2 to return to baseline after burning all fossil fuel is -Million years = more quickly than the residence time of CO2 against silicate weathering.

• If we burn the entire fossil fuel reservoir in the next few hundred years, we could increase the amount of CO2 in the atmosphere by 4-5x the pre-industrial average. This corresponds to global average temps 5-8 degrees higher for a few thousand years.
  (Solution = dont burn as quickly)

While this would take a substantial toll on human civilisation, the planet would be fine as the carbonate-silicate cycle buffers CO2 and temperature on million year timescales.

Question 23

Carbon-silicate cycle including biological productivity:

Answer 23

Biological activity increases silicate weathering which reduces C02.

C02 increases surface temperatures which increases biological productivity = cycle.

This model returns to normal more quickly than just using silicate weathering alone as it includes biotic enhancement of weathering.

Question 24

What in earths past has the carbonate-silicate cycle been seen to operate?

Answer 24

• The faint young sun paradox
• Snowball earth
• The paleocene-Eocene thermal maximum

Question 25

What did the snowball earth cause?

Answer 25

A breakdown of the carbonate-silicate cycle

Question 26

How was the earth warm when the suns luminosity was weaker?

Answer 26

he Faint Young Sun Paradox refers to the apparent contradiction between the early Sun’s relatively low luminosity and the presence of liquid water on the Earth’s surface. According to current models of solar evolution, the Sun’s luminosity was about 70% of its present value during the Archean eon, which lasted from about 4 to 2.5 billion years ago. However, geological evidence indicates that the Earth had liquid water on its surface during this time, which suggests that the greenhouse effect was stronger in the past than it is today.

One possible explanation for this paradox is that the Earth’s atmosphere underwent significant changes during the Archean eon, which allowed it to maintain a relatively warm climate despite the Sun’s lower luminosity. One hypothesis is that the early Earth’s atmosphere was rich in greenhouse gases, such as carbon dioxide and methane, which would have enhanced the greenhouse effect and kept the Earth’s surface warm. However, this hypothesis is still the subject of ongoing research and debate.

Another possibility is that the early Earth’s atmosphere was influenced by the activity of microbial life, which could have altered the composition of the atmosphere through the production and consumption of gases. For example, early photosynthetic organisms may have contributed to the removal of carbon dioxide from the atmosphere through the process of photosynthesis, leading to a decrease in the greenhouse effect over time.

Overall, the exact mechanisms by which the Earth’s atmosphere responded to the Faint Young Sun Paradox are still a matter of active research, and there is much that remains to be learned about the complex interactions between the Earth’s climate, the Sun’s activity, and the evolution of life on Earth.

Question 27

What has the carbonate-silicate cycle (and biological meddling) done over earths history?

Answer 27

It has drawn down CO2

Question 28

What caused the snowball earth?

Answer 28

One possibility is that the Earth’s climate was driven into a deep freeze by changes in the planet’s orbit, such as variations in the tilt of the Earth’s axis or the shape of its orbit around the Sun. These changes could have led to a decrease in the amount of solar radiation that reached the Earth’s surface, triggering a cooling of the atmosphere and the formation of extensive ice sheets.

Another possibility is that the Snowball Earth events were caused by changes in the Earth’s atmospheric composition. For example, it has been suggested that a decrease in the amount of carbon dioxide in the atmosphere could have triggered a runaway cooling effect, as this greenhouse gas helps to trap heat in the Earth’s atmosphere. This could have led to a decrease in the temperature of the oceans, which in turn would have led to the formation of extensive sea ice and glaciers.

Finally, it has been proposed that the Snowball Earth events may have been caused by a combination of several factors, including changes in the Earth’s orbit and atmospheric composition, as well as variations in the amount of solar radiation that reached the Earth’s surface. Further research is needed to determine the relative importance of these different factors in driving the extreme glaciation of the Proterozoic eon.

Question 29

When did the snowball earth happen?

Answer 29

The “Snowball Earth” hypothesis suggests that the Earth experienced several episodes of extreme glaciation during the Proterozoic eon, which lasted from about 2.5 billion to 541 million years ago. The most severe of these episodes is known as the “Sturtian-Varangian glaciation” and is thought to have occurred around 717-635 million years ago. During this period, it is believed that the entire Earth’s surface was covered in ice and snow, with even the equatorial regions experiencing glaciation.

The exact duration of the Snowball Earth episodes is still a matter of debate among scientists, as the geological record from this time period is incomplete and difficult to interpret. However, it is generally believed that the Sturtian-Varangian glaciation lasted for several million years, with some estimates suggesting a duration of up to 10 million years. The Snowball Earth hypothesis proposes that the extreme glaciation was eventually ended by a buildup of greenhouse gases in the atmosphere, such as carbon dioxide and methane, which led to a rapid warming of the Earth’s climate and the melting of the ice sheets. This in turn triggered a feedback loop in which the melting ice led to further warming, eventually returning the Earth to a more temperate state.

Question 30

What geological evidence is there for a snowball earth?

Answer 30

Glacial deposits: Glacial deposits have been found in rocks dating back to the time period of the Snowball Earth events. These deposits include tillites, which are sediments that have been eroded and transported by glaciers, as well as dropstones, which are rocks that have been carried by ice and dropped into sediment layers.

Cap carbonates: Following the end of the Snowball Earth events, a series of thick carbonate deposits, known as “cap carbonates,” were deposited on top of the glacial deposits. These carbonates are believed to have been formed by the dissolution of carbon dioxide in the oceans following the melting of the ice sheets.

Isotopic ratios: Isotopic ratios of carbon, sulfur, and other elements in the sedimentary rocks of this time period suggest significant changes in the Earth’s biogeochemical cycles, indicating a shift in the global carbon cycle that is consistent with the idea of a Snowball Earth.

Paleomagnetic data: Paleomagnetic data from rocks of this time period show evidence of significant changes in the Earth’s magnetic field, which could be explained by the presence of extensive ice sheets that disrupted the flow of the Earth’s molten core.

Taken together, these pieces of evidence support the idea that the Earth underwent several episodes of extreme glaciation during the Proterozoic eon, and that these events played a key role in shaping the geology and climate of our planet.

Question 31

What has the movement of continents been like over the past few million years?

Answer 31

The movement of continents from 540 million years ago to the present day is a long-term process that is typically divided into two distinct periods: the Paleozoic Era (540-250 million years ago) and the Mesozoic and Cenozoic Eras (250 million years ago to the present).

During the Paleozoic Era, the supercontinent of Gondwana began to form, as several smaller land masses collided and merged together. By the end of the Paleozoic, Gondwana had become one of the largest land masses on Earth, covering much of the southern hemisphere. In the northern hemisphere, another supercontinent known as Laurasia began to form, which would eventually merge with Gondwana to form the supercontinent of Pangaea.

During the Mesozoic and Cenozoic Eras, Pangaea began to break apart as tectonic plates shifted and moved. The Atlantic Ocean began to open up, separating North and South America from Africa and Europe. India began to break away from Antarctica and move northward, eventually colliding with Asia to form the Himalayan Mountains. Australia also began to drift away from Antarctica and move northward.

Overall, the movement of continents over the past 540 million years has been driven by plate tectonics, as the Earth’s crust is broken up into a series of large, moving plates. While this movement is slow and gradual, over millions of years it can have a profound effect on the shape and geography of our planet.

Question 32

What is paleomagnatism?

Answer 32

Paleomagnetism is the study of the Earth’s magnetic field as recorded in rocks, sediments, and other geologic materials. The Earth has a magnetic field that is generated by the motion of molten iron in the outer core of the planet. This magnetic field is similar to that of a bar magnet, with a north pole and a south pole.

When magma or lava cools and solidifies, the magnetic minerals in the rock become aligned with the Earth’s magnetic field at the time of cooling. By measuring the orientation and strength of the magnetic minerals in rocks, scientists can determine the direction and intensity of the Earth’s magnetic field at the time the rock was formed.

Paleomagnetism is a powerful tool for understanding the history of the Earth’s magnetic field and the movement of tectonic plates (orientations can be preserved for billions of years). By studying the magnetic properties of rocks of different ages and from different locations, scientists can reconstruct the movement of continents over time and gain insights into the processes that drive plate tectonics. Paleomagnetism can also provide information about the climate and environment of the past, as changes in the Earth’s magnetic field can affect the way that cosmic rays and other high-energy particles interact with the atmosphere.

Question 33

How to escape a snowball earth?

Answer 33

scaping a Snowball Earth scenario would require a significant increase in atmospheric greenhouse gases, such as carbon dioxide, to trap more solar radiation and warm the planet. There are several potential ways that this could happen:

Volcanic activity: Large volcanic eruptions can release significant amounts of greenhouse gases into the atmosphere, leading to a warming effect. However, this would require a sustained period of volcanic activity on a global scale.

Carbon cycle feedbacks: As the Earth’s surface freezes over during a Snowball Earth event, the ability of the oceans to absorb carbon dioxide from the atmosphere would be greatly reduced. This could lead to a buildup of atmospheric carbon dioxide levels over time, eventually reaching a point where they could trigger a warming effect.

Meteor impacts: Large meteor impacts can release vast amounts of energy, which could potentially melt some of the ice covering the Earth’s surface and trigger a warming effect. However, this would require a very large and well-timed impact.

Ocean circulation can help prevent a snowball earth by transporting warm currents to polar regions.

It’s worth noting that while escaping a Snowball Earth scenario would require a warming effect, it’s also important to avoid warming the planet too much, as this could trigger other negative effects such as sea level rise, ocean acidification, and more extreme weather patterns. Ultimately, the best way to avoid a Snowball Earth scenario is to work to reduce greenhouse gas emissions and mitigate the effects of climate change.

Question 34

What is the affect of ice-albedo in the climate system

Answer 34

It is an example of positive (destabilising) feedback.
(2 negatives make a positive feedback loop)

Temperature decreases ice cover, but ice cover increases albedo which decreases temperature.

Positive feedback amplifies initial perturbation which leads to de-stabilising

Question 35

What overall feedback loop does the carbonate silicate cycle produce?

Answer 35

It produces a negative feedback on atmospheric CO2

Atmospheric co2 increases surface temp, which increases rainfall. This rainfall increases silicate weathering rates which reduces atmospheric co2 (draws down co2)

Question 36

How does the positive ice albedo feedback affect a snowball earth?

Answer 36

Once the snowball earth is fully initiated, the positive ice albedo feedback overwhelms the ability of the carbonate silicate cycle to maintain control over surface temperatures on 10(5)- 10(6) year timescales.

Surface temp increases silicate weathering. Weathering decreases CO2. CO2 increases surface temps.

Surface temps decrease ice cover. Ice cover increases albedo. Albedo reduces surface temps.

Question 37

What cycle takes over in the long term?

Answer 37

Over 10’s of millions years, CO2 concentration will grow higher and higher, eventually reaching into the 1% level, and allowing the greenhouse effect to wrestle control over the temperature from the albedo, and leading to rapid melting. (Build of of GHG from volcanoes)

Question 38

What are cap carbonates?

Answer 38

They are large carbonate deposits with sedimentary features indicating rapid deposition and they directly overlie glacial diamictites left in the snowball earth.

Rapid re-equilibration of the carbonate-silicate cycle driven by intense chemical weathering in a hot climate, drawing down CO2 into these carbonate deposits.

Question 39

What was the Paleocene-Eocene Thermal Maximum (PETM)?

Answer 39

The Paleocene-Eocene Thermal Maximum (PETM) was a period of rapid global warming that occurred about 56 million years ago, at the boundary between the Paleocene and Eocene epochs. During the PETM, global temperatures rose by about 5-8°C over a period of around 20,000 years, which is a relatively short period of geological time.

The cause of the PETM is still the subject of scientific debate, but one leading hypothesis is that it was triggered by the release of large amounts of carbon into the atmosphere, either from volcanic activity or from the melting of methane hydrates on the seafloor. This influx of carbon led to a feedback loop, in which the warming caused by the initial carbon release led to further release of carbon from the oceans and soil.

The PETM had significant impacts on the Earth’s climate and ecosystems. The warming led to changes in ocean circulation, sea level rise, and shifts in the distribution of plant and animal species. The PETM is also notable for being one of the best analogs we have for current climate change, as the rate of carbon release during the PETM is comparable to the rate of carbon emissions from human activities today. Understanding the PETM and its impacts can help us better predict and prepare for the future impacts of climate change.

Question 40

Long-term inorganic carbonate silicate cycle overview:

Answer 40

• Regulatges imbalances in the mid-term carbon cycle on the order of 10(5) - 10(6) years
• Critically, there is a key dependancy on climate and CO2, which combine to hold temperatures around (slightly warmer than) current conditions.
• This feedback (which works abiotically, but is influenced by biology) may be responsible for the long term constancy of earths climate. It depends on the positive feedback between global surface temps and silicate weathering rate, which continues to be studied intensively.