GEO 308 Final Exam Study Guide
Mechanisms of genetic variation and evolution - mutation, natural selection, isolation, migration
- Mutation is when new genetic traits appear in a population via errors in DNA replication - Natural selection is when traits favorable to survival are more likely to be passed on to successive generations (this determines which traits will be inherited in a population and which traits will die out). - Isolation is the subset of a population that is physically separated and no longer interbreeds with the rest of the population; often a result of geographic, climatic, or habitat berries. Isolated populations develop different genetic characteristics over time. - Migration is the exchange of genetic characteristics between formerly separate populations.
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Greenhouse effect - what makes a gas a greenhouse gas, examples; describe changes in greenhouse gas concentrations (changes over last few hundred thousand years observed in Vostok ice core vs. recent changes since Industrial Revolution)
A greenhouse gas is transparent to shortwave radiation from the Sun, it absorbs longwave radiation emitted by the Earth at specific wavelengths. The net effect then is that incoming visible radiation passes through the atmosphere and the atmosphere absorbs most outgoing infrared radiation. Examples of greenhouse gases include; carbon dioxide, methane, ozone, nitrous oxide, and halocarbons.
Anaerobic vs. aerobic metabolism, advantages and disadvantages
Aerobic metabolism requires oxygen while anaerobic metabolism does not. Anaerobic metabolism was used by all organisms until Earth's atmosphere oxygenated. Anaerobic metabolism is also inefficient with a low energy yield, meaning that a high energy compound can't be metabolized and organisms would lack energy needed to maintain specialized organelles. Additionally, anaerobic metabolism requires a large surface to volume ratio which keeps anaerobic cells small and cannot form multi-cellular organisms. Aerobic respiration is more efficient than fermentation (anaerobic respiration) and additionally, does not need a large surface to volume ratio meaning that cells can grow larger and become multi-cellular.
Meteorological impacts on air quality, importance of inversions and how they form
Air pollution and meteorology are strongly related. There are three main meteorological factors that directly effect the levels of air pollutants. In a temperature inversion, temperature increases with height, leaving cooler, denser air near the surface and lighter air above. This limits vertical mixing and traps pollutants near the ground surface and increases their concentrations. Wind speed and directions are also important meteorological impacts in that they determine where emissions go and how quickly they dilute and disperse. High winds are required to assist in the break-up of temperature inversion environments.
Effects of origin of life and evolution of photosynthesis on atmosphere - changes in carbon dioxide, oxygen, and methane; corroborating evidence in geologic record - banded iron formations - how they formed and what they tell us about how and when the atmosphere changed
As life evolved on Earth, it modified the atmosphere, weakening the greenhouse effect as the Sun grew stronger; keeping temperatures within range for liquid water. The evolution of life was a major driver of subsequent changes in atmospheric composition. Early life forms were strictly anaerobic respirators because there was no free O2 in the atmosphere - so the released methane as a by-product; meaning the atmosphere was rich in methane. ~3.5 bya cyanobacteria (or blue-green algea) evolved which were prokaryotes that utilized photosynthesis; this meant that they released O2 as a by-product, representing free O2 that could remain in the atmosphere. The evolution of photosynthesis meant a decrease in both CO2 (carbon dioxide) and CH4 (methane) - because carbon dioxide was converted to O2 and methane oxidized to carbon dioxide. Geologic evidence of this change is found in iron-bearing rocks (such as banded iron formation - sedimentary marine rocks rich in iron oxide) that indicate the transition from anoxic to oxic atmosphere.
Types of information different proxies provide about climate - marine sediments, ice cores, tree rings
Climate proxies are natural archives that are sensitive to changes in climate and can be used to estimate climate conditions prior to the modern period. The information yielded from such proxies can provide important information into the potential causes of climate change and improves climate prediction capabilities. - Tree rings can give information for a few thousand years. - Glaciers and Ice cores can give information for a few 100,000s of years - Marine and lake sediments can give information up to a few million years
Evolution of plants - gymnosperms, flowering plants
Ferns and mosses were the first land plants, appearing in Silurian. Gymnosperms were the first group of plants to use seeds for reproduction, first appearing in Devonian and dominated the land by Triassic. Angiosperms first appeared in early Cretaceous and utilized insects for pollination; they provide food (nectar) to the pollinator who then spreads the pollen to other flowers. The advantages of angiosperms is that the fertilization process is not random and requires less pollen and seeds are in protective vessels.
How can we change the long-carbon cycle and atmospheric CO2 concentration via changes in rock weathering (climate, uplift) and magma production (rates of seafloor spreading and subduction)
Changes to the long-term carbon cycles and levels of atmospheric C02 can occur via changes in rock weathering because of its reaction to changing climates. In warming climates rock weathering increases which speeds the removal of C02 from the atmosphere, weakening the greenhouse effect and stabilizing the climate. In a cooling climate this effect would be the opposite where rock weathering would slow and the removal of C02 would also slow. Additionally, rock weathering increases with an increased surface area of rock exposed to chemical weathering - the exposed surface area of rock can be altered via tectonic collisions, uplift, and mountain building. The rate at which magma is produced can also influence the concentration of atmospheric C02. When there is slow seafloor spreading less magma is produced which in turn lessens volcanic degassing (of course the opposite occurs during times of more rapid seafloor spreading). These spreading rates will change over geologic time - there is more oceanic crust that is made during periods of continental break-up and would increase C02 input into the atmosphere.
How are climate models used to study causes of past climate changes and predict future changes?
Climate models are used to simulate past temperature variations and provide insight into the underlying causes that lead to such climates. Climate models can then be used to simulate the Earth's historical and current temperature variations and through a comparison of the results to measured changes can provide insight into the underlying causes of climate changes. These models must be inclusive of both natural and human driven forcing's on the environment.
Tectonic processes and continent formation and break-up: terrane accretion and continental collision, how continental crust is made; continental rifting: rift valley to ocean basin
Continents are assembled from pieces of crust too light to subduct by terrane accretion and collision. - Subduction consumes intervening oceanic crust - Accretion and volcanism adds buoyant material to overriding plate - Intervening oceanic crust destroyed, continents collide. Continental crust is made by accretion of buoyant materials as ocean crust is subducted (which builds continent outward over time), and by the melting of subducted plate and matle (which makes magmas enriched in silica relative to ocean crust).
Formation of solar system and earth, terrestrial vs. Jovian planets
Jovian or Jupiter-like planets are large and composed mostly of gaseous materials like H (hydrogen) and He (helium) that condensed at lower temperatures further from the Sun. Terrestrial or Earth-like planets are smaller and composed mostly of rocky materials like iron that condensed at higher temperatures closer to the Sun.
Marine invertebrate faunal groups - Cambrian, Paleozoic, Modern. Relative importance of each group over time and how it was affected by extinction events, examples of invertebrates in each group
Major changes in diversity of marine invertebrates over time produces three distinct evolutionary fauna (Cambrian, Paleozoic, and Modern). The most important group of invertebrates in the Cambrian faunal group is the trilobites; which where completely extinct by the end of the Permian. Cambrian fauna diversified rapidly during the period. Paleozoic fauna appear in Cambrian and examples include brachiopods and crinoid. These diversified rapidly in Ordovician with maximum diversity in Devonian and declines in diversity since. These were replaced in dominance by modern fauna after the Permian extinction. Modern fauna first appear in Cambrian and diversified slowly during the Paleozoic period; diversifying more rapidly after Permian - they are dominated by mollusks.
Plate boundaries and tectonic setting: divergent plate boundaries, convergent plate boundaries, transform plate boundaries, hotspots; processes occurring in each tectonic setting and examples
Divergent plate boundaries occur at ridges, where crust is pulled apart and melting within the asthenosphere causes magma by decompression - this magma is then cooled to make a new ocean crust. An example of a divergent plate boundary can be found at an ocean ridge that is above sea level, in Iceland. In contract, convergent plate plate boundaries occur when two plates collide, rather than being pulled apart. The type of collision either results in the creation of a trench by subducted, dense plates, or the development of thicker or raised mountains due to plates that are too buoyant to be subducted. An example of this type of plate boundary can be seen in the Juan de Fuca and North American plates. Lateral motion between plates, without convergence or divergence are transform plate boundaries that occur due to falting and earthquakes. The San Andreas Fault is an example of a transform boundary between Pacific and North American plates. A hotspot is a plume of hot rock rising from deep mantle by decompression or addition of water. Hotspots are a source of magma well below the lithosphere that doesn't move with plates, but rather the plate passes over the magma source which results in a chain of progressively older volcanoes (hotspot track), such as the Hawaiian Islands. A tectonic setting is the geologic environment of area relative to any nearby plate boundaries or hotspots. In divergent plate boundaries the tectonic setting is the lithosphere being created, while convergent boundaries is the lithosphere being recycled.
The United States oil supply, where does it come from, peak oil and the future of fossil fuels
Domestic oil production is only able to meet ~31% of the United States' oil demand, so the US imports oil from 88 other countries. Primary suppliers include Canada, Mexico and Venezuela. As far as the future of fossil fuels goes, it is a finite, nonrenewable source that will be depleted - we just don't know when. Estimates at this time show that with the current global oil consumption and the remaining resources, the Earth's supply of fossil fuels will only last for another ~50 years. Peak oil is the time when the extraction rate of oil peaks and starts to decline, or the time when oil is most abundant in the global marketplace. This is not the end of oil, but the end of cheap or affordable oil.
How do isotope ratios in marine sediments record changes in ice volume, including how increases and decreases in ice volume are reflected in the delta value of marine sediments
Evidence for changes in climate during the Pleistocene on Milankovitch time scales can be found in marine sediment cores. Deep ocean marine sediments are largely calcium carbonate shells precipated by Protista called foraminifera, which are single celled planktonic organisms (float in the ocean) that secrete a calcium carbonate shell. The isotopic composition of the these carbonate shells (the ratio of heavy to light oxygen isotopes in the carbonate) are in equilibrium with ambient sea water. This marine carbonate sediment provides continuous record of global ice volume changes that are needed to identify the timing of glacial and interglacial cycles.
Explain how each of these forcing's changes Earth's radiation budget - sunspot cycle, orbital cycles changes in atmospheric particles or GHGs, explosive volcanic eruptions, clouds, snow and ice cover
External forcings include; the amount of radiation produced by the sun (sunspot cycles), changes in Earth's orbit around the sun (orbital cycles) tectonic activity, and catastrophic events, such as volcanic eruptions. Internal forcings include; the amount of type and gases and particles in the atmosphere, or greenhouse gasses, rock weathering, snow, sea ice, glaciers, and ice sheets, and atmospheric and ocean circulation patterns. These are all factors that affect climate and thus affect changes to the Earth's radiation budget (the interaction of energy with Earth's atmosphere)
Explain how and why isotope ratios in glacier ice cores record changes in air temperature (temperature determines how strong fractionation effect - preference for light isotope - is): Delta more negative = more cooling during vapor transport and condensation (glacials, stadials), snow depleted in heavy isotopes, concentrated in light isotopes. Delta closer to zero (less negative) = less cooling during vapor transport and condensation (interglacials, interstadials), snow has more heavy isotopes, less concentrated in light isotopes
Glacer ice cores are excellent archives of climate information. As snow washes water soluble particles from the atmosphere. Material then settles out of the atmosphere and is added to the snow pack. As snow then compacts into glacial ice, bubbles are sealed off and trap samples of ambient atmosphere. Glacier ice has then preserved a record of atmospheric gases and particles which can be drilled to recover this record. The ability for glacier ice cores to record such records will depend on the strength of fractionation which is in turn dependent on temperature. At colder temperatures there is more fractionation with strong bias against heavy water molecules and is delta more negative. At warmer temperatures there is less fractionation with a weaker bias against heavy water molecues, causing slightly more heavy isotopes to get recorded and is thus delta less negative.
Earth's internal structure: layers of different composition; layers of different physical properties
In terms of chemical composition, the earth is composed of a crust of lighter silicates, a mantle of iron-magnesium silicates, and a core of what is suspected to be iron. The physical properties or behavior of the earth are broken up into the Lithosphere which is a hard solid, the asthenosphere which is a soft solid (close to its melting point), the mesosphere which is a hard solid, the outer core which is liquid and then the inner core which is a solid.
Paleoclimate using stable isotopes - ratio of heavy/light isotopes measured relative to standard Delta positive = more heavy isotopes (018, D); fewer light isotopes (016, H) Delta negative = fewer heavy isotopes (018, D); more light isotopes (016, H)
Isotope ratios are reported using "delta" notation. The ratio of heavy to light isotopes in a sample are relative to standard. Ice sheets are delta negative which have fewer heavy isotopes and are lighter, while oceans are delta positive, have more light isotopes and are heavier.
How did the marine sediment record confirm the Milankovitch theory of the Ice Ages? How is the marine sediment record able to do this, while other types of paleoclimate information such as ice cores, tree rings, and continental glacier moraines cannot?
Marine sediments are largely calcium carbonate shells that are precipitated by Protista called foraminifera (single celled planktonic organisms) that secrete a calcium carbonate shell. These shells record changes in isotopic composition, or the ratio of heavy to light oxygen isotopes. The isotopic composition of seawater changes as ice sheets grow and decay. The calcium carbonate shells of foraminifera in marine sediments record these changes and provide a record of global ice volume on land. This record shows cyclic variations of the global ice volume at the same scale of ice advance and retreat in Milankovitch cycles.
What is the evidence for greenhouse gas concentration changes on Milankovitch timescales? What are the causes of these changes (carbon dioxide, methane)? Evidence that supports these explanations?
Most CO2 change between glacial and interglacial climates can be explained through changes in ocean productivity, related to increased availability of iron to the ocean during glacial periods. Iron is an essential micronutrient used by phytoplankton because Iron is necessary to make chlorophyll which is the pigment used for photosynthesis. Insolubility of iron in an oxygenated environment limits the availability of iron to the ocean and therefor limits ocean productivity. During colder/drier glacial periods there is an increase supply of iron bearing dust to the ocean which fertilizes the ocean and stimulates greater primary productivity, greater uptake of other nutrients - including greater uptake of CO2 as a biomass. Methane changes can be explained on Milankovitch timescales too. The largest natural source of methane today is tropical wetlants; anoxic sites of anaerobic microbial activity, including methane producing bacteria. Paleoclimate records show that tropic regions were drier during glacial climates where wetlands would shrink and methane emissions would decrease (the opposite in wetter, interglacial climates).
Why do carbon cycle processes make periods of continental collisions "icehouse" climates and periods of continental break-up "greenhouse" climates?
Mountain building and continental collision increases rock weathering, which strengthens the geologic sink for C02 and ultimately reduces the greenhouse effect; this means that periods of continental collision, such as the Ordovician-Silurian, Carboniferous-Permian and Neogene-Quaternary, are associated with cold, "icehouse" climates. In contrast, periods of continental break-up are associated with "greenhouse" climates because the movement of the continents occurs from events of high seafloor spreading rates and increased volcanism which are sources of atmospheric C02 and increase the greenhouse effect; thus there is a warmer, or "greenhouse" climate.
Long-term carbon cycle - rock weathering, ocean mineralization, subduction and volcanism
On long timescales of the carbon cycle, there is an exchange of carbon between geologic materials and atmosphere by slow geologic processes. Such processes involved in this long-term carbon cycle include rock weathering, ocean mineralization, subduction and volcanism. In summary, the process starts with rock weathering which uses atmospheric C02 (sink), then through ocean mineralization carbon is stored as carbonate on the seafloor, and subduction and volcanism (sources) return C02 into the atmosphere.
Causes of changes - 1920-1945, 1945-1975, 1975-present; role of natural forcings (i.e., solar), role of human activities (i.e., carbon and sulfur emissions)
Over the last 150 years the Earth has experienced many variations of climate. From 1920-1945 temperatures were shown to have warmed which is potentially explained by geological events such as sunspot cycles. Then, from 1945-1975 there is evidence of stabilization, meaning that there was a lack of warming, which cannot be explained by natural forces on such a short timescale. From 1975-2010 we can see peaks in warming temperatures that are most likely explained by human activities, rather than natural/geological forces. Other potential explanations for the variability of temperature trends, rather than true changes in climate, like the overall warming trend since 1850, could potentially be explained by El Nino Southern Oscillations and Pacific Decadal Oscillations. Exponential increases in the use of fossil fuels post 1945 initially associated with no temperature trend 1945-1975 when both sulfur (cooling) and carbon (warming) emissions were increasing. Reductions in sulfur emissions after 1975 allowed warming by CO2 to dominate, which is still increasing.
Planetary accretion and differentiation, and how they made plate tectonics possible
Planetary accretion is the process by which planets form by gravitation attraction and impacts between smaller fragments. Planetary differentiation is a result of accretion, where kinetic energy is converted on impact to heat resulting in melting of inner planets. This means that for Earth, the molten earth segregated into layers of different densities (heavy elements sank to form core [iron], lightest elements rose to form crust, intermediate created the mantel), in turn creating the possibility of plate tectonics due to the reaction of the different layers.
Feedbacks - differences between positive and negative feedbacks, include examples
Positive and negative feedbacks refer to the strength of a feedback effect; either amplifying or minimizing. The Ice-Albedo feedback is an examples of a positive feed back because it promotes large changes to cooling effects. This can be observed almost as a circular , self-fulfilling event where the initial change is cooling, promoting more surface snow and ice, reflecting more solar radiation and producing less head or amplifying the cooling. Rock-weathering feedback is a type of negative feedback due to its effect of promoting stability and minimizing changes. In an example of warming climate, rock-weathering is increased which removes CO2 from the atmosphere; and due to being a green-house gas, this means that there is a promotion of cooling, ultimately reducing the warming effects.
Role of carbon cycle processes, positive (ice-albedo) and negative (rock weathering) feedbacks in freezing and thawing of Snowball Earth, importance of continents being concentrated in topics
Processes of the carbon cycle as well as positive and negative feedback events could have had rolls in the freezing and thawing of a Snowball Earth. Climate feedbacks are climate responses that amplify (positive) or minimize (negative) change. With specific consideration to the theory of Snowball Earth, the geographic location of the continents in the tropics exposed rocks to higher rates of weathering (due to warmer and wetter climates) which due to high rates of removal of C02 created a weak greenhouse effect and allowed for ice growth at polar latitudes. With the start of ice sheet growth, the ice-albedo effect would create a positive feedback, enhancing the cooling climate and providing further growth and expansion of ice sheets; and once ice cover reached approximately 30` latitude high ice-albedo resulted in runaway glaciation and thus a Snowball Earth. Rock weathering, a negative feedback which typically stabilized positive feedback effects like ice-albedo, failed in Snowball Earth due to the concentration of the continents in tropical latitudes. Rock weathering would have continued on those continents because they remained ice free (even though there were growing ice sheets in the polar latitudes); this meant that the ice-albedo was unchecked and allowed for runaway glaciation. With the Earth being frozen there would be no rock weathering and no photosynthesis so there would be no sinks for atmospheric C02. However, atmospheric C02 was still being released via volcanism. Although it would take a significant period of time, when C02 reached high enough levels via volcanism, melting would be triggered and initiate the reversal of the ice-albedo feedback. For a period of time the Earth experienced a cycle of rapid thawing and rapid glaciation through the processes explained above and was only broken when enough plate tectonics moved enough land out of tropical latitudes to allow the negative feedback from rock weathering to stabilize atmospheric C02.
Radiative forcing - internal vs. external forcing's
Radiative forcing are factors that affect climate - mechanisms that cause climate change. - External forcings occur outside the climate system and are not affective by climate. Examples include changes in solar luminosity and changes in Earth's orbit. - Internal forcings are changes that occur internal to the climate system and respond to climate change and create feedbacks. Examples include carbon cycling and greenhouse gas concentrations, as well as albedo changes due to snow and ice cover.
Differences between solar and terrestrial radiation, how blackbody radiation explains these differences, how atmospheric gases and particles interact with solar and terrestrial radiation
Solar radiation is shortwave and mostly visible, while terrestrial radiation is longwave and mostly infrared. This is because the surface temperature of an object determines the wavelength of energy emitted; the Sun emits energy at a short (visible) wavelength because the surface is hot, whereas the Erath re-emits that energy at a longer (infrared) wavelength because Earth is much cooler than the Sun.
Trends in air pollution and acid rain, is the Clean Air Act working?
Recent trends in emissions have shown a drop in the use of coal for fuel and/or power which has caused a decrease in the concentration of acid rain failing over areas where coal burning is most prominent. Sources of nitrogen oxides are burning of fossil fuels which contain NO and NO2 compounds, which mainly comes from vehicle exhaust. Recent trends in emissions has shown a slight decline and in many states across the US have implemented strict and rigorous emissions standards for vehicles to abide by. Environmental effects of nitrogen oxides are acid rain (in particulate form), and it is involved in the production of ozone which is the main component of photochemical smog. The Clean Air Act has been far more successful in reducing emissions of sulfur dioxide, as reductions in sulfur emissions started as soon as the Clean Air Act was passed in the 1970s and are now less than half what they once were; whereas nitrogen oxides finally peaked in the 1990s and have only recently begun to decrease.
Explain how and why isotope ratios in marine carbonate sediment record changes in global ice volume - due to fractionation of water isotopes during evaporation: Delta more + = larger ice sheets (glacials), ocean concentrated in heavy isotopes, light isotopes trapped in ice. Delta closer to zero (less +) = smaller ice sheets (interglacials), light isotopes returned to ocean as ice sheets melt.
Seawater isotopic composition changes as ice sheets grow and decay. Calcium carbonate shells of foraminifera in marine sediments record these changes which provides a record of global ice volume on land. Less ice on land means that the ocean is isotopically lighter and is delta less positive. More ice on land means the ocean is isotopically heavier and is delta more positive. Fractionation is the change in isotope abundance during phase changes, such as evaporation.
Snowball Earth - when, where, evidence (glacial deposits, dropstones, BIF, "cap" carbonates and what they mean)
Snowball Earth is a theory based on geologic evidence that the entire Earth was covered in ice for long periods of time in the late Proterozoic era, between 600-800 million years ago. Areas where rock that date back to the 600-800mya time range show evidence of glaciation and can be found of every continent today. Such geologic evidence is easily identified as being sediment deposited by glaciers by their wide range of sizes (deposits by other weather phenomena are almost always similar in size); including fine sand to very large boulders. Striations also provide evidence that rocks were dragged across other rocks during the movement of glaciers. Dropstones are an additional signature of glaciation, which is essentially misplaced chunks of rock that occur in otherwise finely laminated marine sediments (occurring through ice-rafting where by the rocks are moved in the glacier and when the ice melts the rocks sink to the bottom of the ocean and becomes incorporated into sediment). The Snowball Earth theory also explains the reappearance of banded iron formations (or BIFs) because as the snowball Earth began to warm and ice cover was removed, the water was re-exposed to oxygen and allowed iron to dissolve, oxidize and deposit as BIFs. Snowball Earth additionally explains "cap" carbonates. Cap carbonates are a layer of carbonate rock found directly above glacial deposits of the snowball earth era, and are unusually heavy in carbon isotope ratios. These reflect the intense rock weathering that occurred during the thawing of Snowball Earth.
Describe the solar radiation distribution that favors glacials, including the phase of each cycle that produces this distribution. Do the same for interglacials
Solar radiation that is distributed to create minimum summer radiation in the Northern Hemisphere, meaning distributions that favor glacials include; a more elliptical orbit (high eccentricity), lower axial tilt (low obliquity) and a precession that results in the Northern Hemisphere summer when Earth is farthest from the Sun. In contrast, interglacials are favored when each cycle results in warmer summers in the Northern Hemisphere, which include; a more circular orbit (low eccentricity), a high axial tilt (high obliquity), and a precession that results in the Northern Hemisphere experiencing summer when Earth is closest to the Sun.
Age of earth - relative and absolute dating techniques, how do we know that Earth is very old?
Stratigraphy is the study of particular sequences and ages of rock layers. These ages can be determined by specific studies, such as superposition or correlation, depending on the type of rock. Relative age places specific rocks and geological events in chronological order such as oldest to youngest. Absolute age is when stratigraphers assign specific dates in years. For sedimentary rocks, superposition would be used where the bottom layers of geological material are the oldest and the youngest material is at the top since sediment settles at the top of whatever surface area is exposed at the time. For igneous rock, correlations are sought to determine age based on areas of similar fossil types that are present. We know that the Earth is very old, because the oldest known mineral on Earth is thought to be ~4.4 billion years old; an estimate that was made using radiometric dating techniques.
Ozone: good stratospheric ozone vs. bad ground level ozone
Stratospheric ozone is good because it absorbs UV radiation which protects us living on the surface from the harmful effects of high energy radiation. Ground ozone in the troposphere is naturally only found in small amounts, but areas where there are volatile organic compounds, nitrogen oxide, sunlight, and oxygen, lead to the production of ozone in the lower atmosphere which creates smog, a human health risk (eye and lung irritant), and kills vegetation.
Specific examples from geologic record - Carboniferous glaciation, Cretaceous greenhouse - What geologic events where occurring in each period, and how did they effect the carbon cycle and climate?
The Carboniferous-permian is a period of continental collision that is associated with the formation of Pangea. Because this was a period of continental collision and creates a period of a cold and cooling climate due to the rate of removal of C02 from the atmosphere and the decrease in the greenhouse effect. The Cretaceous-Paleogene occurred approximately 150-40mya and was a period of continental break-up. Due to high rates of seafloor spreading and volcanism this was a period of increased C02 input and thus a warmer, "greenhouse" climate.
Cretaceous and Permian mass extinctions - causes, evidence, organisms affected
The Cretaceous and Permian mass extinctions are associated with two catastrophic events; Deccan flood basalt and an asteroid impact on the Yucatan peninsula. Both may have been contributors considering the Deccan eruption would have stressed the global environment and the asteroid impact would have dealt the final blow.
Earth as a system - components of Earth system, open vs. closed systems, why is Earth best considered a closed system?
The Earth system is composed of four parts: the atmosphere, the hydrosphere, the biota (living organisms), and the solid Earth. The Earth is best considered a closed system because it exchanges only negligible amounts of matter with its surroundings. Closed systems gain and lose energy from their surroundings but not matter. The Earth receives tremendous amounts of energy from the Sun and radiates much of that energy back to space. However, any gains or loses of matter from Earth are very small relative to the mass of Earth, so Earth essentially functions as a closed system - open to energy but not matter.
Faint Young Sun paradox and changes in strength of greenhouse effect over time
The Faint Young Sun paradox states that early in Earth's history the Sun was ~25% weaker than it its today and that the Sun's energy output (luminosity) has increased over geologic time (at a rate of ~1% per 150 million years). The early atmosphere of Earth had higher greenhouse gas concentrations and these greenhouse effect grew weaker as the Sun grew stronger which meant that the atmosphere was more reliant on CO2 and sensitive to small changes - setting the state fro the "Snowball Earth" in the late Precambrian. (With current levels of greenhouse gases, Earth would not have been warm enough to support liquid water until 1.7 bya - Earth would have been frozen for the first 3 billion years).
Holocene climate variability: evidence and causes - 8200 year event, early Holocene optimum, Medieval Warm Period, Little Ice Age; examples of impacts of Holocene climate change on people
The Holocene is the current interglacial period and began 11,750 years ago at the end of Younger Dryas cold event. This geological time period is characterized by warmer and more stable climate compared to that of glacial periods. The 8200 year event is the largest amplitude climate event in the current interglacial period and produced a widespread cold and dry period that lasted for ~300 years (having started 8200 years ago. Evidence for this event can be seen in the cooling of the North Atlantic through more delta negative oxygen isotope values in the Greenland ice core as well as drying in the tropical latitudes as seen by a decrease in methane concentrations. The early Holocene climate optimum was a warmer and drier climate in the Northern Hemisphere mid-latitudes than present climates with a peak in Northern Hemisphere summer radiation due to Milankovitch cycles. The Northern Hemisphere subtropics were wetter than present climates with stronger and northward shifted summer monsoons. The medieval warm period was a period of generally warmer conditions and was best observed in the Northern Hemisphere and particularly the North Atlantic. Norse colonies settled and prospered during the medieval warm period but by the end of this geological time period the settlements declined and abandoned by the start of the Little Ice Age. The Little Ice age was a period of climate cooling which caused inadequate crop growth and expanded sea ice making travel difficult.
Climate and environmental policy - goals of Kyoto Protocol and Montreal Protocol, provisions for developed and developing countries
The Kyoto Protocol is an international treaty designed to mitigate the effects of climate change due to greenhouse gas emissions. The protocol states that scientific uncertainty must not prevent precautionary action to limit climate change and requires developed countries, which are responsible for most of the greenhouse gas emissions to date, to take the lead in slowing global warming. The Kyoto Protocol is designed to stabilize atmospheric CO2 concentrations at 550 ppm. This represents an approximate doubling of atmospheric CO2 concentrations from their pre-industrial concentration of about 280 ppm and would be the highest CO2 concentrations the earth has seen in at least one million years. The provisions of the Kyoto Protocol require the 38 developed nations to cut greenhouse gas emissions to 5% below 1990 levels by 2012. The Kyoto protocol does not require developing nations to cut emissions until later versions of protocol, and allows emission trading among participating countries for the right to produce greenhouse gas emissions, providing further incentive for countries to cut emissions by allowing them to "sell" their excess emissions capacity. The Montreal Protocol is a landmark international agreement, or treaty, to protect the stratospheric ozone layer. The treaty was originally signed in 1987 and amended in 1990 and 1992. The Montreal Protocol established a schedule for phasing out the production and use of compounds such as chlorofluorocarbons (CFCs) that destroy the stratospheric ozone layer and also allows countries to "trade" the right to produce a particular substance as long as the total production permitted by the schedule is not exceeded. The Protocol established a dual standard for developed and developing countries by allowing developing countries to delay their compliance with the control measures for 10 years, and established a fund financed by developed countries to provide assistance to developing countries in phasing out CFCs. The Montreal Protocol limitations on CFC use are expected to lead to a recovery of the ozone layer by 2045. This success demonstrates that the countries of the world are capable of decisive action to mitigate harmful environmental effects. Although not addressing global warming directly, CFCs are greenhouse gases and will be phased out by the protocol. The Montreal Protocol could serve as a model for climate change initiatives such as the Kyoto Protocol which seek to limit the production of greenhouse gases.
Is the Montreal Protocol working?
The Montreal Protocol is an international agreement to phase out substances that deplete ozone; this includes CFCs, hydrochlorofluorocarbons (HCFCs), hydrobromofluorocarbons (HBFCs), carbon tetrachloride, methyl chloroform, methyl bromide. Results of the Montreal Protocol are promising; chlorine abundances peaked in the mid 1990s but has been slowly declining since. Overall the emission controls on CFCs and related compounds is expected to lead to complete recover of ozone layer by 2045. This is a huge success because it demonstrates that world countries are capable of decisive action to reduce emissions that are causing environmental problems and could serve as a model for limiting pollutants that cause climate change such as C02.
PDO - what is it, climate impacts of + and - PDO in U.S., role in inter-decadal climate variability
The Pacific Decadal Oscillation or PDO is a pattern of climate variability that is expressed most strongly in the North Pacific outside of the tropics and on a long timescale, 10-20+ years. The PDO phases modulate temperature trends where warming is expressed during +PDO phases and suppressed during -PDO phases. .........................................................
Importance of feedbacks in producing climate change on glacial-interglacial timescales: amplification of Milankovitch forcing by changes in albedo and greenhouse gas concentrations
The affect of ice sheets on albedo amplified radiative forcing on Milankovitch cycles as the growth of ice sheets increases albedo and amplifies cooling but the retreat of ice sheets decreases albedo and amplifies warming. Ice core samples show evidence of cyclic changes in GHG concentrations that also amplify radiation changes due to orbital cycles. CO2 and CH4 are shown to be in higher concentrations during interglacials and lower during glacial periods.
Building blocks of life - amino acids and genetic material, structure of DNA and importance of the distinction between L and D amino acids
The building blocks of life include deoxyribonucleic acid, or DNA which passes the plan for organization, growth and reproduction on to the next cell. DNA is formed in a double helix with two polymers (alternating sugar and phosphate molecules) which is connected by paired bases (compound containing nitrogen, guanine (G) pairs with cytosine (C) and thymine (T) pairs with adenine (A)). Additionally, life requires amino acids, particular either L-amino acids or D-amino acids which are chemically identical but structurally mirror images of each other. It is important to note the distinction between L and D amino acids because ALL living organisms are exclusively made up of L-Amino acids and L-amino acids can only react with other L-amino acids (meaning that any theory for the origin of life must explain this exclusiveness).
Carbon cycle - reservoirs, processes, and forms of carbon; processes as sources or sinks
The carbon cycle is the movement of carbon through the Earth system. - Reservoirs where carbon is found include; the atmosphere, biosphere, oceans, geologic materials. - Processes that exchange carbon between reservoirs can include photosynthesis, decomposition, rock weathering, mineralization, metamorphism and fossil fuel use. - Forms of carbon include C02, organic carbon, fossil carbon, bicarbonate ion and carbonate rock. - Sources release C02 from biologic, oceanic, or geologic reservoirs into the atmosphere, these can include; respiration, burning of biomass and fossil fuels, metamorphism and volcanism, and degassing from seawater. - Sinks remove C02 from the atmosphere and stores it in biologic, oceanic, or geologic reservoirs, these can include; photosynthesis, burial of biomass in sedimentary rocks, rock weathering and dissolution in seawater.
Carbon cycle - reservoirs, processes, and forms of carbon; processes as sources or sinks
The carbon cycle is the movement of carbon through the Earth's system. - Reservoirs where carbon is found include the atmosphere, biosphere, oceans and geologic materials. - In order for carbon to move between reservoirs it is exchanged via processes such as photosynthesis, decomposition, rock weathering, mineralization, metamorphism and fossil fuel use. - The forms of carbon include C02, organic carbon, fossil carbon, bicarbonate ion and carbonate rock and can be exchanged between such forms. - There are also processes that change the amount of carbon in the atmosphere. Sinks are processes that remove C02 from the atmosphere and stores it in biologic, oceanic, or geologic reservoirs (these include; photosynthesis, burial of biomass in sedimentary rocks, rock weathering and dissolution in seawater). Sources, on the other hand, release C02 from biologic, oceanic, or geologic reservoirs into the atmosphere (these include; respiration, burning of biomass and fossil fuels, metamorphism and volcanism, and degassing from seawater).
Role of India's collision with Asia in Cenozoic cooling and Pleistocene Ice Ages, why does uplift increase rock weathering and CO2 removal, importance of Asian monsoon to this story
The collision of India and Asia affected the acceleration of cooling in the Cenozoic era due because it increased rock weathering by uplifting the Himalaya and Tibetan Pleateau and the development of a strong monsoon in Asia that created increased precipitation, also further increasing the rate of rock weathering.
Discovery of plate tectonics: evidence for continental drift, evidence for seafloor spreading, evidence for subduction (How were these processes discovered? How do we know they happen if we can't directly watch them?)
The continental drift theory includes evidence that coastlines at one point fit together, distribution of fossils that show species movement along continents that have since separated and similar types/ages of rocks on widely separated coastlines. Evidence of seafloor spreading can be shown in stripes of rocks on the seafloor that show reversals of normal and reversely magnetized rocks that are symmetric on either side of the ridge. Subduction is the process that removes old oceanic crust (discovered by relationship of deep earthquakes to trenches - earthquakes are deeper with distance from trench; volcanoes are also concentrated in chains next to trenches; occur above depth where subducting crust causes melting in mantle).
History of early life and its geologic evidence - carbon isotope ratios, stromatolites, eukaryotes, Edicarian fauna, Cambrian explosion
The earliest evidence for life on earth is not found in fossils, but rather based on isotopically light carbon (12C). There are two stable isotopes of carbon: 12C and 13C with 12C being organic and lighter and 13C being inorganic and heavier. This enrichment in 12C indicates biological processes. The earliest unequivocal fossil evidence for life is in fossil stromatolites (layered structures) in 3.5 billion year old rocks. The early forms of life on earth were single celled prokaryotes with no cell nucleus that were anaerobic in metabolization, because Earth's early atmosphere contained no free oxygen. Photosynthetic cyanobacter then evolved 3.5 bya which slowly changed Earth's atmosphere from CO2 rich to O2 rich. ~1.5 bya is the earliest unequivocal fossil evidence of eukaryotes, but there are biomarkers that suggest their presence as long as ~2.5 bya (it took this 2-3 billion year time span for Earth to develop an oxygenated environment suitable for eukaryotes). The edicarian fauna are the first multi-celled animals which evolved ~600 mya. They were jelly-like creatures with no hard parts and they represent the large jump in complexity from single-cell eukaryotes. They are followed by a large increase in biological diversity and complexity in early Cambrian, known as the Cambrian Explosion. The Cambrian Explosion was an increase in diversity of marine invertebrates and shows evidence of the first animals with hard parts and the first chordates (or animals with a spinal cord). There are phyla still around today that evolved during this period including Mollusca, and Arthropoda.
First life on land, characteristics
The first life on land had to have structural support, the ability to conserve water and an ability to exchange gases directly with the atmosphere. These included arthropods which were invertebrate animals with segmented bodies and jointed legs, such as crustaceans, spiders and insects.
Characteristics of the five biological kingdoms - prokaryotes or eukaryotes, single or multi-celled, how they obtain food - producers (chemosynthetic, photosynthetic), consumers, and/or decomposers
The five biological kingdoms include: Monera, Protista, Plantae, Fungi and Animalia. - Monera is the only prokaryote kingdom, made up entirely of single-celled organisms. Some are producers (photosynthetic or chemosynthetic), while others are decomposers and utilize aerobic (with oxygen) or anaerobic (without oxygen) metabolism. * The oldest forms of life on Earth (Archea) are chemosynthetic bacterial organisms that are categorized in this kingdom. - Protista are all single-celled, producers (photosynthetic) or consumers. - Fungi are all multi-cellular, decomposers - Plantae are all multi-cellular, producers (photosynthetic) - Animalia are all multi-cellular, consumers
Smog formation, acid rain formation, where are these a problem?
The formation of photochemical smog is highly weather dependent. You need sunlight, and ideally inversion to concentrate pollutants at ground level. Environments that favor photochemical smog would be long days of summer coupled with a strong high pressure system, resulting in strong sinking motions in the atmosphere. Acid rain is formed through a reaction of sulfuric and nitrous acid, which lowers its pH level to ~4.5 and produces rain that is approximately eleven times more acidic than normal, "natural" rain. Within the US both photochemical smog and acid rain are more pronounced problems along the East coast and parts of the West coast where there are heavier and more concentrated emissions of SOx, NOx and VOCs.
Explain what happens to solar radiation intercepted by the Earth in qualitative terms - incoming solar radiation, albedo, outgoing terrestrial radiation, greenhouse effect
The interaction of energy with Earth's atmosphere and surface ban be described by Earth's radiation budget. Incoming solar radiation is either reflected (albedo) or absorbed. Absorbed energy is then re-emitted at longer wavelengths that interact with atmospheric trace gases (greenhouse effect). Albedo is the fraction of solar radiation reflected without absorption or warming and changes with the amount of snow or ice on the surface, or with the clouds/sulfate in the atmosphere. The greenhouse effect is the absorption of longwave radiation by atmospheric trace gases.
What is the mid-Pleistocene transition? How is it explained? What is the supporting evidence?
The mid-Pleistocene transition is a change in the length of glacial cycles that occurred approximately 800,000 years ago, before a domination of obliquity and after a domination of eccentricity Milankovitch cycles. During this transition glaciations lasted longer and were more intense but occurred without any change in Milankovitch cycles. ......?(Lecture 19)
Composition of modern atmosphere; how does the modern atmosphere compare to the pre-biotic atmosphere and why are they different?
The modern atmosphere is composed of abundances of permanent atmospheric gases that vary only on very long geologic time scales. These atmospheric gases include; nitrogen, oxygen, argon, neon, helium, krypton and hydrogen. There are also abundances of atmospheric trace gases that are all greenhouse gases and most are increasing due to human activities; these include; carbon dioxide, methane, nitrous oxide, ozone, and water vapor. Earth's pre-biotic, or Archaen atmosphere was similar to that of Mars and Venus, rich in CO2 with trace amounts of oxygen. Without the evolution of photosynthesis, the atmosphere would still be rich in CO2.
Nature of fossil record, factors favoring preservation of fossils
The nature of the fossil record is that there are divisions of Phanerozoic time based in part on fossil record due to the fossil record being spotty and incomplete and only providing snapshots of evolution at discrete points in time. Additionally, organic remains are fragile, requiring special conditions to preserve these remains as fossils in stratigraphic record. Meaning that the organism must be rapidly buried and have anoxic conditions that limit decomposition. Lastly, only organisms with hard body parts - bones, shells, teeth, etc., are preservable as fossils and such organisms did not appear until the Cambrian period.
What is the ozone hole? Why is it best developed over Antarctica? How do CFCs cause ozone loss?
The ozone hole is an area of increased ozone destruction that was first discovered in Antarctica where the reactions that destroy ozone from CFC products is most favored. Tropical geographical areas that experience more solar radiation has shown very little observation of ozone destruction. CFCs are compounds that contain chlorine or bromine and contribute to ozone loss. These compounds were once widely used as ingredients in everyday products from refrigerants to solvents and food containers. If these chemicals are not broken down in the upper atmosphere, then reactions that take place on polar stratospheric clouds convert unreactive chlorine and bromine compounds into more reactive forms; which under the right conditions, destroy ozone.
Evolutionary relationships between fishes, amphibians, reptiles, birds, mammals; geologic periods and evolutionary advances made by each group, geologic events that spurred their evolution and affected their diversification
The periods of the Early and Middle Paleozic era are Cambrian, Ordovician, Silurian and Devonian.The earliest vertebrates where fishes that evolved from chordates during Cambrian. These then evolved into the first land vertebrates, the lobed-finned fishes during Devonian. These lobed-fins eventually evolved into legs which appeared on the first amphibians by the end of Devonian. Amphibians were then the only land vetebrates for 75 million years and flourished during the Mississippian and Pennsylvanian periods because they were tied to water for reproduction and there were abundant suitable habitats during this time. During the Permian period, however, there were vast deserts that covered Pangea and the interior of the large continent was far from oceanic moisture sources. This then produced the evolution of reptiles which replaced amphibians as dominant land vertebrates. These Permian reptiles are more closely related to mammals than to dinosaurs. These primitive permian reptiles then gave rise to two groups; the Archosaurs, or "ruling reptiles" (including dinosaurs, marine reptiles and flying reptiles) and mammals and mammal-like reptiles.
Scientific method - what does it mean to be a hypothesis and theory, how does a hypothesis become a theory?
The scientific method is a process of five steps that scientists move through to tests hypothesis and prove theories. The five steps are: observe, hypothesize, predict, test and modify. A hypothesis gradually gains widespread acceptance by repeated testing and modification while a Theory is a hypothesis that withstands scrutiny over time (predictions tested and shown to be accurate).
What characteristics made Earth suitable for life to originate? Characteristics that define life?
There are four characteristics that define life, including: metabolization, growth, self-replication, and evolution. Earth is suitable for life due to characteristics such as; the right distance from the sun (not too hot or too cold), right size (enough gravity to hold an atmosphere), and a magnetic field to shield surface from cosmic radiation.
How do we study Earth's interior? How do we know Earth's core is iron?
There are several ways in which we study Earth's interior. We can make direct observations by drilling (up to 15 km), exposures of mantle rock at the surface and material erupted by volcanoes. We can also make indirect geophysical observations regarding Earth's magnetic field (suggesting a molten, metallic core), Earth's gravity field (known from the mass and average density of Earth), and Earthquake seismic waves (caused by changes in velocity and travel path - suggesting thickness and physical state of Earth's crust, mantel and core). We can make a quality educated guess that Earth's core is made of iron due to observations noted above, as well as evidence from meteorites that are abundant in iron (iron additionally provides the needed density to total the known volume of Earth).
Milankovitch cycles - eccentricity, obliquity, precession, their timescales, explain how each cycle affects the amount and/or distribution of solar radiation received by the Earth
There are three Milankovitch orbital cycles, including; eccentricity which is effected by the shape of Earth's orbit, obliquity, or the degree of tilt of the Earth's axis, and precession, or the wobble of Earth's axis. Eccentricity is the cycle where Earth's orbit changes from more elliptical to more circular, taking 100,000 years to complete one cycle. This change effects the total amount of radiation Earth receives; receiving less radiation during times of more elliptical orbit because the distance between the Sun and the Earth is, on average, greater. Obliquity is the cycle that takes 41,000 years to complete and is the change of the Earth's axis between 21.5' and 24.5'. This change in tilt affects seasonal distribution of solar radiation where a low tilt = less seasonality because solar radiation is more evenly distributed (a low tilt also favors glaciation). Precession is the direction of Earth's rotational axis, or its wobble. This cycle effects the timing of summer and winter season in relative to the distance of Earth from the Sun, or its position in orbit; meaning that it affects the distribution of solar radiation between Northern and Southern Hemispheres. Today, Earth's precession is such that Northern Hemispheres receive a smaller percentage of total solar radiation and summers are relatively cool and winters are relatively warm (this would be opposite halfway through a precession cycle).
Hypotheses for the origin of life - evidence supporting each hypothesis; problems that exist with each hypothesis or unresolved questions
There are three theories for the origin of life. - The primordial soup hypothesis that suggests complex organic molecules formed by reaction of simple molecular building blocks concentrated on the ocean's surface (which contained ingredients for amino acid and protein synthesis). Evidence that supports this theory include experiments that show amino acids can be produced from chemical reactions involving gases present in early atmosphere CH4, NH3, H2). However, a problem with this hypothesis is that organic molecules at the ocean's surface would have been destroyed by ultraviolet radiation. - The extraterrestrial origin hypothesis poses a theory that life originated elsewhere and arrived on Earth from comets or meteorites. Evidence supporting this hypothesis include meteorites and comets that contain organic molecules, including amino acids (mostly L-amino acids). There is even a Martian meteorite discovered in Antarctica that contains structures that may be fossilized bacteria. The problems with this hypothesis are that it only proposes an explanation for how life got here, not how it formed; also how could living organisms survive space travel? - The Hydrothermal vent hypothesis suggests that life forms evolved around submarine hydrothermal vents, which location provides reduced sulfer compounds for energy and protection from ultraviolet radiation. Evidence supporting this theory include genetic analysis which shows Archaebacteria (most primitive life forms on Earth and closest living link to ancestors of all life) are found today at hot springs and vents. Questions that still remain regarding the formation of life are; how did amino acids form proteins? How did proteins become self-replicating? and How did metabolic reactions begin?
Carbon tax versus cap and trade: how would each work?
There are two basic policy options for promoting decarbonization of the economy: a cap and trade system and a carbon tax. In a cap and trade system, a limit to the total allowable CO2 emissions is set. Credits allowing a certain amount of carbon emissions are distributed to the various industries and sectors covered by the cap and trade system. The number of available credits totals the total allowable emissions in any given time frame (the "cap"). Businesses must reduce their emissions to match the emission credits they hold or face penalties. Businesses that reduce their emissions further can sell their excess credits to other business (the "trade"). The other basic policy option is a carbon tax. Carbon-emitting activities are taxed, based on their carbon intensity, to encourage lower carbon intensity alternatives. The most likely way to implement a carbon tax would be to tax energy producers at rates equivalent to their carbon emissions per unit of energy (their carbon intensity). The tax could later be expanded to other carbon emitting activities, such as agriculture, timber, waste disposal, etc.
Causes of mass extinctions - flood basalts, extraterrestrial impacts, evidence for these events in the geologic record, environmental consequences of these events
There are two leading hypotheses for mass extinctions, including volcanism and impact events. - Volcanism would have caused mass extinctions by causing large volumes of magma to erupt in geologically short periods of time - CO2 and sulfur gases would cause warming and acid rain. Evidence of this theory are seen in flood basalts and changes in ocean sediment chemistry. The Deccan Basalt Eruption, erupted near the time of the Cretaceous extinction and scientific research has shown a strong correlation between eruptions and extinction rates. - Impacts could have caused mass extinctions due to the dust created by impact which causes a "nuclear winter." Geologic evidence of this includes; impact structure, iridium, tektites, and shocked quartz. Alvarez and Alvarez discovered evidence of a possible impact event by boundary clay rich in iridium (common in extraterrestrial material - asteroids, meteorites). Effects of a Cretaceious-Paleogene impact would have been earthquakes of >10 magnitude, tsunami's, global forest fires sparked by molten rock raining from the sky, vaporized rocks producing CO2 and sulfuric acid dust blocked sunlight for years shutting down photosynthesis.
Types of air pollutants: NOx, SO2, VOCs, ozone, particulates, major sources
Types of air pollutants includes gases; sulfur dioxide (SO2), Nitrogen oxides (NO and NO2 - NOx), carbon monoxide (CO), Ozone (O3), and volatile organic compounds (VOCs). Particles are also types of air pollutants including combustion - black carbon (soot), and gas to particle conversions - SO2 to sulfate, NOx to nitrate. Primary pollutants are emitted directly into the air and include sulfur dioxide, nitrous acid, carbon monoxide, volatile organic compounds and black carbon. Secondary pollutants are produced in the atmosphere by reactions between primary pollutants and include sulfate, nitrate and ozone. Main sources of air pollutants include stationary sources such as power plants (these are a main source of SO2, and particulates), mobile sources, such as cars, trucks and airplanes (main source of CO), and for nitrogen oxide, volatile organic compounds, and lead, the sources are equally spread between stationary and mobile sources.