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GEOG 205 Global Changes
Lecture 1: 08/01
What to know - Time Scale
Describe the nature of the geological time scale:
What was its original basis?
A very relative scale with not much absolute time since it was based on the law of superposition.
How is it subdivided?
Into, Era (largest), periods and Epochs (smallest)
Know the names and absolute times of the eras and periods and epochs represented in read in the text below.
Cenozoic Era:
Its most recent Period of the Quaternary started 2.6 million years ago Comprised of two Epochs: the Pleistocene and Holocene
What are the complications of fitting the Anthropocene into the geologic time scale?
The time frame of its start date is not clearly defined. It is difficult to integrate it into the geologic time scale because of how to classify it as an Epoch, an era or a period. The anthropocene has more to do with human cultural development than it does with geological change, though humans did have impact. Furthermore, human development was not evenly distributed throughout all regions, there was variation of impact based on location and advancements. It is difficult to define when this would have started. It is not well defined enough to have a unique point that corresponds to every criteria of the Geological time scale. We are unsure where it ranks within the periode, epoch and age classification. Any decision of classification will contradict something.
Time and the Anthropocene
When, How long and what rate these changes occurred
Geological time is subdivided into
ERAS
PERIODS
EPOCHS
Geologic time scale
Sedimentation often provides a relative time scale. There are no “absolute” numbers, it's the law of superposition that allows guesstimates.
Isotopes and dating has allowed more exact dating
Concerned with the Cenozoic, but specifically the Quaternary.
She may ask to know the general time frame of them, not exact numbers but you should know
Cenozoic Era:
its most recent period, Quaternary Period 2.6 million years
Its two Epochs
Pleistocene Epoch
Holocene Epoch 11.7 thousand years ago
Quaternary began about 2.6 million years ago.
Final exam question is to order all the events up to the present age**
ALMHYLPgiPg
Anthropocene: a time in which humans have replaced nature as the dominant environmental force on Earth (shaping ecology as well as geology). This is relevant to the Geologic Time scale
Dating techniques
What to know - Dating technique
Can you explain why reversals in the Earth's magnetic field helps us to date ocean sediments?
Paleomagnetism, based upon changes in the earth’s magnetic field recorded in sedimentary rocks, can be used for much older material, but provides ages simply within a period of a few thousand years. This is observable through the configuration of the sediment, how it settled on itself based on its magnetic properties.
What are the limitations of radiocarbon dating in terms of time and material that can be dated?
The materials that can be dated are only those that were made up of what was once living organisms. So animal and plant origin material. In terms of time, we cannot know how many carbon atoms the organism had before it died unless we know how much was in the atmosphere during its life.
What is the half-life and what is its significance in terms of ability to date material? What is the age limit of radiocarbon dating and why does it have a limit?
Half life is the radioactive decay of atoms, half of the available atoms shift over a specific period of time. Carbon 14 is radioactive and unstable, it decays and changes to other elements. The age limit of radiocarbon dating is around 40 000 to 50 000 years since the concentration of carbon 14 was too low at the time.
How abundant is C14 relative to other carbon isotopes?
It is not nearly as abundant as C12 which is about 98.9 percent or C13 which makes up 1.1 percent
Has the atmospheric concentration of 14C been constant? Why is it critical in C14 dating?
The atmospheric concentration has not been constant, this is critical to dating because the variations depict a specific year.
How can the study of tree rings be used to calibrate (refine) the ages we get from radiocarbon dating?
The comparison of trees in the same region of various ages. Comparing the patterns in the ring width to determine when certain environmental events happened. This cross referencing helps date. It is an annual record.
Why is the time span dateable by dendrochronology not limited to the age of the oldest living tree?
Dendrochronology is used in archeological survey and can be used for trees that are long dead and ones that were used to build ancient monuments and buildings
Paleomagnetism
Declinations are used to date the ocean sediment with magnetism that stacks onto itself
Carbon 14 dating
very useful for the quaternary
Isotopes
Stable Carbon 12 has a mass of 12. 6 protons, 6 neutrons. 98.89% of all carbon
Stable Carbon 13 has an atomic weight of 13. 6 protons and 7 neutrons 1.11% of all carbon
Unstable and radioactive, decays into another element. Carbon 14 has an atomic weight of 14. Atoms have a nucleus with 6 protons and 8 neutrons.
Nitrogen can become carbon. This is what makes carbon 14, produced in the atmosphere
Carbon 14 is taken up by plants. It decays in plants and animals, the atoms become part of tissue in bone or muscle.
The rate at which it decays is called a half life
Production of Carbon 14 in the atmosphere is not constant but variable due to the magnetic field
Calibrations for the date using tree rings
Dendrochronology
start with living tree, and measure the ring width which can vary over time with thinner and thicker rings (based on environmental condition with moisture for example) ring width responds to regional climate
Examine rings in a dead tree of the same region and species.
We look for overlap between the old and the new. This can be used in archeological context
FILL IN
Lecture 2: 01/13
What to know? - climate and weather
5. In what form is the radiation incoming from the sun and in what form is it re-radiated and why is it important to the Earth’s climate?
Radiation incoming is from solar energy in the form of visible waves and short waves (70%) and the re-radiation is 30% that is reflected back and scattered by clouds. Some is absorbed by the clouds, others by the earth surface. This radiation enters the earth and warms the surface. These Infrared and long form waves often get radiated back down and trapped in our atmosphere. This is what causes the greenhouse effect on earth's climate.
6. Can you explain what controls the absorption and reflection of these two forms
of radiation?
It is atmospheric gasses and their absorption depends on composition of the earth's surface. Surfaces absorb heat more than air, especially darker ones. The earths atmosphere absorbs 95% of the longwave radiation. Reflection occurs when the radiation cannot be transformed into heat.
7. What roles do clouds play in radiation received or lost?
Clouds trap heat, they contribute to heat retention by preventing the outgoing radiation from the earth's surface to leave and escape our atmosphere. It is most frequent at the lowest layer of the atmosphere.
8.Can you sketch Hadley cells and explain what happens to temperature and
precipitation of air masses as they move through these cells?
Hadley cell circulation is a large-scale mode of convection of advection that transports sensible heat. This circulatory mode transfers heat in the northern and southern hemispheres avoiding the equator. The tropics along the equator have more precipitation due to rising and sinking flows of the Hadley cells. The ascent of humid air rises to the poles and cools down as it descends again.
Large amount of heat stored in low latitude ocean provides most of the fuel that runs earth's climate system. Energy is exchanged among water, land and air
9.Can you list 3 non-anthropogenic greenhouse gases besides CO2?
Methane
Nitrous oxide
Water vapour
Hydrofluorocarbons
Carbon tetrafluoride
10. How is the heat redistributed around the Earth?
Convection currents try to equalize heat everywhere. Heated air at the equator rises up to be spread towards the poles.
11. What is the difference between sensible and latent heat?
Sensible heat is the product of temperature of the air and its specific heat. It is heat that is felt/sensed which is carried by air or water.
Latent heat is what happens when air is warmed. energy absorbed or released by a substance during a change in its physical state (phase) that occurs without changing its temperature. For example as water freezes the temperature does not change but it is energy that is lost. Same concept as condensation with water vapour becoming liquid.
Sensible heat causes a change in the temperature of a substance without changing its phase. Heating water from room temperature to boiling involves this type of heat. Latent heat is the energy required to change the state of a substance without altering its temperature.
12.Can you described water vapour feedback?
There is positive feedback in the climate system with water vapour. Warmer atmosphere can hold more water vapor. Increased coz means climate is warmer, this increased greenhouse trapped, meaning more water can be held.
13. Can you explain: albedo, the Coriolis effect, orographic influences on
précipitation?
Albedo is the percentage of incoming radiation that is reflected. Often reflected by snow, sand, clouds. Forest has low albedo, so though it does have fantastic carbon storage, it does not help with reflecting out incoming radiation. Incoming radiation is more reflected when the sun is lower in the sky
Coriolis effect
Worlds constant movement, because there is more space at the equator than at the poles, there is faster eastward movement at the equator.
It affects bigger slower movement fluids like water and air.
Coriolis effect differs the winds from the poles so that they move east and west and not just to the low pressure at the equator
Orographic influences on precipitation talks about cooling and evaporation based on elevation. Example of the very mild and wet climate of BC near the coast that contrasts with the desert on the other side of the mountain
Difference between climate and weather? How to understand climate?
Climate is long term averages measured across multiple years, it tell us what we should expect to see and weather is in the short term forecasts.
What's responsible for seasons?
It's not the proximity to the sun. It is the tilt of it and which side of the earth is closest to the direct rays.
The earth's tilt. When the earth is angled towards the sun, the rays hit it directly so it is warmer. and vice versa with indirect rays. Indirect rays mean that the rays cover a larger area but lose the force of concentration the more it is spread out.
The ellipse is uneven but not actually by that much so it is not the proximity to the sun
What are equinoxes and solstices?
They are opposites. They are thanks to the earth's tilt.
It is based on how far north or south the sun is from the equator.
Solstice marks the start of summer and winter. They are the longest and shortest days of the year.
Equinox marks printemps and fall to mark when day and night are of equal length.
Why are the poles colder?
If the earth were flat, the poles would not be different temperatures from the rest of the world
Sun radiation energy varies bc of curved surface. Its spread over a greater area,
the rays are more indirect up there, rather than the direct ones from the equator. Its focused on a larger area
The part of the spectrum that affects climate is the visible light that we have from ultraviolet to infrared
Nature of incoming radiation is different from what is reflected back. This is due to the nature of the surface of the earth. Some infrared radiation is absorbed and reflected by clouds
Without atmospheric gases the earth would be 31 degrees cooler
Gases have global warming potential
Albedo is the incoming radiation reflected rather than absorbed.
Often reflected by snow, sand, clouds.
Forest has low albedo, so though it does have fantastic carbon storage, it does not help with reflecting out incoming radiation
Incoming radiation is more reflected when the sun is lower in the sky
BASICALLY POLES ARE COLDER BECAUSE
They receive less radiation per square meter
They have higher albedo (snow and ice)
The angle of incoming radiation is low
Large amount of heat stored in low latitude ocean provides most of the fuel that runs earth's climate system. Energy is exchanged among water, land and air
Latent heat
energy from cooling and warming climate
Hadley Cell circulation is very large scale mode of convection in which sensible heat is transported
Global atmospheric circulation
Lecture 3: 01/15
EXAM Will need to know the common names of some plants in the different biomes
What to know?- Vegetation and biomes
Can you locate each “biome” on a map?
Can you provide an example of each? Can you recognize examples of each? Can you recognize biomes by their temporal pattern of precipitation and temperature?
tundra
Polar grasslands which have permafrost. Very long winters in extreme cold and 6-8 weeks of summer. Marshes, bogs and ponds are common over there.
Boreal first
Just south of tundra, very far north. Combination of various precipitation and temperatures. Summers are short and mild, winters are long, dry and cold.
Temperate deciduous forest
Moderate average temperatures, long warm summers but not severe winters. Lots of precipitation. Vancouver and Oregon.
Dry woodland and shrublands (also Mediterranean)
Grasslands have enough precipitation to support grasses and a few trees. They are mostly found in the interior of continents in tropical, temperate and polar (tundra) regions. Often with seasonal drought, vast amounts of vegetation is not possible.
Desert (warm and cold)
Deserts have low annual precipitation with an evaporation rate that exceeds this. Found in tropical and subtropical, polar and temperate regions. the temperature can vary by climate but tends to be on the extremes of very hot or very cold.
Temperate grasslands
Prairies like in Saskatchewan with bitterly cold winters and dry summers. Temperate shrubland is like Italy or California with very dry summers.
Tropical savanna
Some are savannas which have long dry seasons which alternate with a heavy rain season. These are also near the equator
Tropical rain forest
Near the equator, lots of moisture, high humidity and rainfall with warm temperatures
What type of vegetation is dominant in each (note the names of some plants)?
Tundra has moss and shrubby plants. These are treeless plains.
Boreal first Few coniferous, evergreen trees, spruce, fir, cedar, hemlock and pine. Low plant diversity for the rest.
Temperate deciduous forest Broadleaf trees like oak, hickory, maple, poplar and beech. Lots of detritivore and decomposers with moss at the ground.
Dry woodland and shrublands (also Mediterranean) Small shrubs, grass and a few trees.
Desert (warm and cold): Vegetation is sparse and widely spread with mostly low plants if any. These often aim to conserve water like cactus and succulents, prickly pear cactus, yucca and agave
Tropical rain forest Huge trees with wide but shallow bases. Broadleaf evergreens plants
Temperate grasslands: Loads of grass, mix of short and long grass. For for mediterranean, it is dense evergreen growth mixed with shrubs.
Tropical savanna low plants and some large trees scattered
Can you rank the biomes by annual precipitation and temperature (i.e., order them on a gradient of temperature or aridity)? Understanding the gradient of aridity
Dessert
Grasslands
Temperate grasslands
How do photosynthesis and respiration play a role in concentration of carbon dioxide in the atmosphere?
Plants use photosynthesis to capture carbon dioxide and then release half of it into the atmosphere through respiration. Plants also release oxygen into the atmosphere through photosynthesis
Carbon + water + solar energy YIELDS + glucose + oxygen
Decomposition releases heat, in compost the center is hot and releases CO2
Lecture 4: 01/20
What to know? The evidence on the Land
Theories about ice ages causes and retreats. Make sure to take notes on that material of the book
What is a glacier?
A glacier is a large, accumulation of crystalline ice, snow, rock, sediment, and often liquid water that originates on land and moves down slope under the influence of its own weight and gravity. At higher elevations, more snow typically falls than melts, adding to its mass. Eventually, the surplus of built-up ice begins to flow downhill. At lower elevations, there is usually a higher rate of melt or icebergs break off that removes ice mass.
What geographic and climatic conditions are required for glaciers to first form?
A glacier forms when snow accumulates over time, turns to ice, and begins to flow outwards and downwards under the pressure of its own weight.
If the accumulated snow survives one melt season, it forms a denser, more compressed layer called firn. The snow and firn are further compressed by overlying snowfall, and the buried layers slowly grow together to form a thickened mass of ice. Each year, new layers of snow bury and compress the previous layers. This compression forces the snow to recrystallize, initially forming grains similar to the size and shape of sugar grains.
Typically, glaciers exist and may even form in areas where:
mean annual temperatures are close to the freezing point.
Winter precipitation produces significant accumulations of snow.
Temperatures throughout the rest of the year do not result in the complete loss of the previous winter’s snow accumulation
In their upper parts, glaciers generally accumulate more snow than they lose from melting, evaporation, or calving.
Higher latitudes, or at the poles
Why does a glacier move, or “flow”?
It moves from the pressure of its own weight. Valley glaciers flow down valleys, and continental ice sheets flow outward in all directions.
Glaciers move by internal deformation of the ice, and by sliding over the rocks and sediments at the base. The weight of overlying snow, firn, and ice, and the pressure exerted by upstream and downstream ice deforms glacier ice, in a phenomenon known as creep. A glacier may slide on a thin layer of water at its base. This water may come from glacial melting due to the pressure of the overlying ice, or from water that has worked its way through cracks in the glacier.
Glaciers can also readily slide on a soft sediment bed that has some water in it. This is known as basal sliding and may account for most of the movement of thin, cold glaciers on steep slopes or only 10 to 20 percent of the movement of warm, thick glaciers lying on gentle slopes.
What evidence for past glaciations exists on land (i.e., geomorphic evidence)? Be able to describe these features and know their names.
Boulders deposited by the movement of ice.
Drumlins: tear-shaped hills. They are all oriented in the same direction. This indicates the direction in which the glacier advanced. It erodes and deposits at the same time. Often eroded by the sea in the Atlantic provinces.
Materials that form the Drumlin are called till. Transported by multiple movements of the ice sheet.
Evidence of tree growth near bodies of water that have formed from the deposit
Striations indicate the direction of ice flow/advance, these are scratches
Fluctuations in the rotations and atmosphere are aligned with the change in ice sheets.
Accumulation of ice compresses the earth, so when it eventually melts, it bounces back up. This is rebound which can effect shorelines
Eskers: these represent channels in the ice flow. They do not indicate ice flow, it is just debris from the glacier. Raised ridges. Sand and gravel found in themis of high quality good for constructions
Glacial till when the ice really starts to melt. These are enormous deposits
Agricultural lands on Ioess soils. Very soft soils and fertile
Moraine, materials collected at the top of the ice sheet. Moraines have been revegetated. Elongated accumulations of rock form along the surface of a glacier
North America: Drifts/tills and moraines
Europe: River terraces and moraines
Large volumes of water leave the glacier and create Deltas (bodies of water)
How was some of this geomorphic evidence used to support the Doctrine of Catastrophism?
It accounted for the fossils, it explained the fossils there without discounting the ideas of the Bible. The idea that some big event happens and all forms of life get erased. A new era restarts after that with new life that stays around until the next one. It is an accepted theory by the Church at the time .
How can geomorphic features or other terrestrial evidence indicate the maximum extent of an ice sheet?
Terminal morraines are excellent indicators of the extent. If the ice sheet is stable, it leaves a moraine. Ice advances until it gets to a latitude thats too warm. Ice is still being pushed down, but it stops and leaves the debris at the terminal moraine
How can geomorphic features or their characteristics indicate the direction of its flow?
Striations of rock indicate the direction and slow scraping of the glacier.
What configuration of the continents is prerequisite for an ice age to occur? How has this configuration changed in the past?
Higher latitudes Freezing and thawing of glaciers. With the continental drift, land masses moved closer to the polls Thus, a feedbackcan occur: ice reflects radiation, does not absorb heat, temperatures drop further, producing more extensive ice coverage, which reflects more light, etc. Once an ice sheet starts to shrink, a comparable reverse feedback loop may be triggered. (That is, less ice, more light absorbed as heat, higher temperatures, more melting, less ice, etc.)
What theories have been proposed to explain the advance and retreat of ice sheets?
Drift theory with Erratic boulders that were the result of icebergs drifting onto shore. This is not the case it is from glaciers.
1) Change in energy output from the sun Because the variability is on time scales of less than 100 years, many scientists consider variations in energy output from the sun an inappropriate explanation for the slow development of major iceages.
2) Uneven distribution of dust particles in space
Dust in space may cause cooling by reducing the amount of the sun’s energy received by the Earth. It has been postulated that the Earth (and its solar system) passed through an area of space where dust particles were concentrated, which in turn screened out the sun's energy enough to initiate a cooling trend. There is a contradictory theory stating that when more dust particles fall into the sun it glows more brightly, which would cause temperatures to rise. There does not seem to be enough evidence to properly test either theory.
3) Concentration of CO2 in atmosphere Carbon dioxide (CO2) is a greenhouse gas. It allows short-wave radiation from the sun to passthrough, but traps the long-
wave radiation reflected from the earth’s surface. A decreased concentration of carbon dioxide would decrease this greenhouse effect, thus a decreased concentration could have caused cooling and an ice age. Our records, in terms of evidence for past concentrations of greenhouse gases, do not support this hypothesis, but many think that past concentrations may have played some role.
4) Volcanic eruptions Volcanic eruptions do affect climate, but the atmospheric changes caused by them are short lived and there is no convincing data to supporting the role of volcanic eruption as an explanation for the long term pattern of Pleistocene glaciations.
5) Vertical movements in the Earth’s crust
The geologists Lyell and Dana suggested this explanation. An increase in land elevation would cause temperatures to drop because that land area at higher altitudes would be cooler. The process of mountain building is too slow and spatially restricted to be an appropriate mechanism. It is thought that these changes could contribute, but not be the trigger.
6) Antarctic Ice Sheet surge This theory is based upon the assumption that the Antarctic ice sheet accumulated and collapsed episodically into the ocean. When the surrounding ocean was covered with reflective ice, temperatures were lowered enough to trigger an ice age. If this had happened we should be able to find evidence of the expanded Antarctic ice sheet, as it would leave a deposit on the sea floor
when it melted. This type of deposit has yet to be found.
7) Ewing-Donn theory
Two scientists, Ewing and Donn, suggested that
an ice age begins when the Arctic Ocean is free
of ice and open to warm North Atlantic currents. These warmer temperatures cause evaporation to increase. As the atmosphere becomes moister, more snow falls on land, allowing accumulation of an ice sheet. Deglaciation would begin when the Arctic Ocean was frozen over, cutting off this moisture supply.
There is some evidence that portions of the Arctic Ocean were previously open,
but this theory has never received much support. Yet, if Ewing and Donn are correct, might greenhouse warming trigger a new ice age? Consider recent news reports of the melting of the Arctic Ocean.
8) Stochastic theory Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas? This was the title of a talk given by Edward Lorenz who recognized that small differences in initial conditions (of weather systems, for example) could produce widely divergent outcomes. That is, the flap of butterfly's wings might create tiny changes in the atmosphere that may ultimately alter the path of a tornado or delay, accelerate or even prevent the occurrence of a tornado in a certain location. The flapping wing represents a small change in the initial condition of the system, which causes a chain of events leading to large-scale alterations of events. Small differences in climate conditions could be amplified to major climate change, possible but not embraced if other explanations seem to fit.
Major force that
Change in energy output from the sun.
Stochastic theory, the theory of chaos and random events
Variability of CO2 in the atmosphere
Vertical movements in the Earths crust. An increase in land elevation would cause temperatures to drops because more area of the earth would be too cool (we dont really accept this theory)
Antarctic ice sheet coverage. Episodic accumulation and collapse of Ice sheet. Howver there is no evidence of this
Ewing-Donn theory. Ice age begins when arctic is free of ice, with warmer temperatures caused more evaporation, thus more snowfall and the accumulation of an ice sheet. But once the arctic is frozen, moisture is cut off and deglaciation begins.
CO2 is greenhouse gas, lower concentrations in atmosphere would reduce greenhouse effect cause cooling (doesnt count)
Dust in Space, passing around the earth blocks sun rays
Four glacial stages were identified based ona river valley and their age is based on the depth of it.
1. Gunz
2. Mindel
3. Riss
4. Wurm
Depression of the earth’s crust and rebound.
Feedbacks are associated with ice cover. It creates more cooling, there is a change in albedo with an encouraged development of ice. Also the accumulation of ice compresses the land more.
How glacier accumulates
From the Albedo feedback loop that reflects more radiation and keeps the environment even cooler. Accumulation exceeds melting, thus changes in summer vs winter temperatures matter. The advance and retreat is based on the ration of accumulation vs melting. Also the amount of precipitation possible is linked to the sea level. At lower altitudes, there is more melting.
Why does a glacier advance and retreat?
CHANGES IN ICE
Lecture 5: 01/22
What to know - Ice age evidence
How can foram species be used to reconstruct paleoclimates?
Forams, these are single celled organisms. Most have calcium carbonate shells. It is the chemical composition of their shells that allows the study of paleoclimates. There are temperature indicators since many different species are adapted to different climats. Changes in temperatures over time are then evident based on which kind of Foram is found there. The chronology is seen through the samples of forams found in ocean sediment.
They are amazingly variable, we can differentiate species by the shape and pattern of their shell. THERE ARE TWO MAIN TYPES
Pelagic forams: Part of the oceans plankton, floating in the upper levels of the sea.
Benthic forams: at the bottom of the ocean. They are consumers of nutrients
Both end up at the bottom of the ocean
Why does the oxygen isotope ratio in forams or glacial ice reflect changes in ice volume during the Pleistocene?
Oxygen 18 is a stable Isotope, unrelated to radioactive decay and are slower and heavier than the more abundant Oxygen 16. The lighter water evaporates more readily from the ocean, but some heavier H2O also evaporates. Within the water vapor, the heavier molecules are the first to condense and fall out as precipitation, and do so over mid-latitudes, before the water vapor reaches the poles. Thus, glacial ice has depleted levels of 18 O (figure 7) . During glacials much of the evaporated, lighter, water does not return to the ocean, as it stays tied up in ice, making the ocean water heavier.
In foram shells The ratio of 18 O/16 O closely tracks the proportion of the world’s water locked up in ice sheets. For each 10-metre change in sea level there is a 0.11‰ change in the δ18O of the CaCO3 in the shells of planktonic forams. This change does not aligns with the type of clib meant to provider aide.
What are some of the complications of using forams for interpretations of paleoclimates and how have they been avoided?
This information does not align with the existing record. Inexact correspondance which makes it hard to tell the exact time
How does the oxygen isotope record of glacials compare to the earlier 4-stage model of glacials? How was the mechanism for major climate change over the Quaternary confirmed?
Ghd four model system is too broad to expect scientists “Spectral analysis”, a statistical technique, was used to detect the patterns of the three orbital parameters in the oxygen isotope record. Once the statistical proof was made, the Croll-Milankovitch theory became again the accepted paradigm for explanation of the major climate fluctuations in the Quaternary
Can you describe how changes in the Earth’s orbital parameters affect climate? On what time scales do they operate? How do they interact
The eccentricity of the earth with the ellipse changed over time. This affects the earth's climate because of our distance from the sun.
Exam question** of how long the cycle is
about 100 000 years on average
The axis and Earth's tilt
Cause long term variation in distribution of seasonal solar insolation received largest change at high latitudes
Amplifies or suppresses seasonality (more tilt amplifies)
If The Earth's tilt is not very great, it does not affect the season much
Ocean studies
Study of sediments cored from ocean bottoms they discovered a significantly more complex record of climate change then initially thought. The record first come from fossil forams
They take a sample of mud from the ocean bottom, their temperature will align with the temperatures of the location/climate they originate from.
There are many cold and warm periods over time.
OTHER PROOF - OXYGEN ISOTOPES
Isotope oxygen -16 haa the atomic weight of 16. The other stable isotopes of oxygen is -18 wight a weight of 18. Oxygen-18 is 13% heavier, meaning it moves more slowly and whatever molecule its included in. 18 is also more abundant. These molecules help with the formation of ice sheets, they are also in the material of foram shells.
The amount of the rare but stable isotope is expressed as the ratio of rare/abundant.
Meteorological distillation Proportionately more of the light oxygen isotope evaporates from the ocean. The lighter water molecules (those containing O16) move more quickly into the air. Near the poles, atmospheric water vapour is increasingly depleted in O18.
The O18 layer of glacial ice also gives a record of climate that corresponds to the stable isotope record from the ocean. Ice contains other signals as well.
Shells of planktonic forams contain 2 signals
Temperature and ice volume.
There is an oxygen isotope radiation pattern everywhere around the world. The same pattern is in all the oceans.
ICE AGES BOOK NOTES
Louis Agassiz Glacial theory (Swiss) P.22 realizing that marks and scars on boulders had to be from a force of pressure and mass which could not be caused by weathering. Thus reinforcing the proof of glaciers
De Charpentier gave glacial theory a irrefutable foothold in the Scientific community to be accepted
Lecture 6: 01/27
READ THE MAINE SURVEY THING
you also need to understand the questions to do the assignment
What to know - Changes in levels of land and sea
What biotic (biome-level) changes resulted from increased aridity during the last glacial maximum?
The sea level decreased by 80-120m, from the lack of condensation bringing the precipitating back into the cycle, this change in volume is a EUSTATIC CHANGE. Since the world's oceans are connected, the loss of water results in a global change in sea levels. There was not much moisture in the air since a lot of the water content was just ice. This made rain forest contract and deserts expand.
What are eustatic and relative sea level?
Isostatic change is a local rise or fall in land levels. A forebulge with ice is an isostatic change, Relative seas level = eustatic + isostatic change.
Eustatic change involves a rise or fall in water levels caused by a difference in the volume of water. It is sea level at a global scale and changes of volume can be caused by climat change.
With stable land, change in location and elevation of the shoreline = change in water volume and increases in water volume = meltwater + thermal expansion
Both components of eustatic sea level change
Transgression Increase in relative sea level, which floods the land
How has the elevation of coastal land changed as a result of glaciation and deglaciation? What are the terms for these changes?
Regression The reverse process, a decline in relative sea level, . Occurred as ice sheets grew and eustatic sea level declined. also occurs on some coastlines not yet
recovered from the loading of glacial ice.
Weight of glacial ice is a significant load on the Earth’s crust and during glaciations caused a depression of the Earth’s surface. The surface responds somewhat like a balloon (of course, much more slowly) and the depression caused by the ice forced the land to rise outside the area under pressure. This increase in elevation around the margin of the ice is termed a forebulge, also referred to as a peripheral bulge by some.
What caused the Champlain Sea to develop?
Isostatic depressions caused inland seas. Depression of the land under the weight of glacial ice as of the rise of water level caused by meltwater released from the waning glacier.
What factors today contribute to increased relative sea level rise?
Heat with the warming of oceans and expansion of molecules
Changes in glacial ice with meltwater
Much land was uncovered which created more diversity of human, plant and animal population. from migration and seeds getting blown around. Such as though the Bering land bridge. Proof is Terrestrial animal remains were found far underwater.
Weight of glacial ice depressed the Earth’s crust
The increase in relative sea level, which floods the land, is referred to as transgression, the reverse process, a decline in relative sea level, is termed regression. Regression, of course, occurred as ice sheets grew and eustatic sea level decline
Lecture 7: 01/29
What to know - Enormous Lakes and Serious Erosion slides
Can you explain what happened to cause the erosion of the Channeled Scablands and approximately when?
Channelled Scablands are caused by movement of large volumes of water over fairly short time periods (days) in events that lasted only days? There are many proglacial lakes
What evidence is there for the existence of Glacial Lake Missoula and the repeated flood/erosion events?
Fine grained sediments and clay have been deposited around the lake. The sediment slits alternate between light and dark layers which indicates the water there. There are proglacial lake deposits from the movements of water. Overall with the proglacial lakes, they change location and size along with connections. This includes links to rivers with their drainage, like with the Mississippi river flowing into Lake Agassiz.
What is catastrophism?
The earth's systems were shaped by catastrophic events. Not the ongoing processes but grand events
Why did the findings of Bretz seem to be a rejection of the Principle of Uniformitarianism?
He found that these Scablands were created in only a matter of days and not from slow erosion. It was a large volume of water over a short period of time.
How can the landscape modifications of cataclysmic events be explained through the Principle of Uniformitarianism?
Processes occurring in the past are the same ones in the present. The physical and chemical principles (e.g. gravity, thermodynamics) that govern geologic processes of the present have also applied in the past.
If we accept that cataclysmic events such as are regular, albeit rare occurrences, then some would maintain that the Principle of Uniformitarianism continues to hold true and some amendments have been made to the Theory of Uniformitarianism. One of these would be that catastrophic events are as much part of geologic history as the uniform action of the everyday processes. So, to properly address Uniformitarianism we might say that the natural laws that govern geologic processes have not changed over geologic time, but the rate at which certain geologic processes operate can var
How is the distribution of aquatic life in Canada related to glacial lakes?
The flooding and submergence of many continents allowed for the migration of many aquatic species. As glacial lakes shift in size and location, bodies of water (other lakes, rivers or oceans) are connected which facilitates the spread of population.
How do GLOFs affect societies/communities today? EXAM GLOF=Glacial lake Outburst floods
In the Hondu River Valley in the Himalayas is very remote and is not affected very much by humans.
It is earthquakes and landslides that have a cascading effect on water levels. These floods and res ult in death, destruction of property and destruction of crops.
There are masses of overhangs from the mountains that pose a risk to communities. If a mass falls into the lake, it can cause a catastrophic outburst flood that will cascade into the rivers and have huge floods. If ice or rock falls into the lake, the rise in water level could breach the fragile earth boundaries (Moraine) that hold the water in. Moraines serve as a dam of sediment. It is for that reason that workers in Butain try to drain lakes in opposite direction from risk zones.
Notes today
Eustatic changes are changes in sea level, changes in the volume. Isostatic changes are changes in the land. Relative sea level change is a mix of eustatic and isostatic.
With the eIce dam disappearing, land is no longer depressed by ice, there is rising ground.
Ice age floods created mega-ripples, similar to that of wind pushing sand at a beach. A LOT of energy is required to create these rock ripples.
Exam question: Does lake Agacie exist today? No.
Lecture 8: 02/03
This is the last lecture of material that will be on the exam
Should watch the “how ocean currents work”
What to know - Rapid Climate Change
What was the Younger Dryas and when did it occur?
This is after the plastocene. The Younger Dryas was a short duration (on the order of 1,000 years) cold event, a stadial, first recognized from evidence in northwestern Europe. (A stadial is a cold period occurring within a glacial or interglacial time. The warmer time between stadials is referred to as an interstadial.) it was 12,900 to 11,600 year ago
What types of evidence are there for the Younger Dryas?
First notice from evidence in Northwest Europe from a short, cold event, this is a “stadial” is a cold period within the present interglacial. Very first evidence was far north and was also seen more south.
In Nova Scoatia and New Brunswick where small glaciers remained, those small glaciers re-advamced. The deposits were Soil, till, soil, till with thicker till layers.
Appearance of the flower indicated the return of the tundra and colder temperatures .
How quickly did the climate change to Younger Dryas conditions?
The onset was only 1000 years long.
What theories have been proposed to explain the cooling during the Younger Dryas?
Haley theory is linked to FILL IN. Cold + salty = dense, dense water winks to form North Atlantic Deep Water
The drop in temperatures cannot be explained by astronomical parameters.
There seemed to be a simple explanation for this regional cooling. The accepted theory (or paradigm) was that, as temperatures warmed, the large ice sheets began to break up, calving icebergs into the North Atlantic. These icebergs floated with ocean currents east across the Atlantic, cooling temperatures across the northern North Atlantic.
How did a change in evidence of this event result in different theories for the cooling?
New evidence indicated (FILL IN) and the Greenland ice core with dust falling on the ice sheet increased.
At Alpine Swamp in New Jersey, the first study showed no evidence of Younger Dryas but new developments in carbon-14 dating allowed us to date very small amounts of carbon such as in a single seed.
How can palynology help us to detect past climate change?
Those pollen assemblage changes signaled an abrupt reversal to a climate comparable to that long recognized in places more than 6° latitude further north. The consensus was now that the Younger Dryas was not restricted to just Eastern Canada and northwest Europe.
Pollen from an arctic wildflower was studied. We look at Spores and pollen. Pollen form may be unique to the species or may be representative of a genus or even a family. The level of Taxonomic resolution is variable but usually good enough to allow a palynologist to get a good idea of the nature of a past plant community from collection of the pollen and spores produced by the plants in the community. If we know what the plant community was, we can tell the biome it was grown in.
What are some of the limitations of palynology and how do scientists deal with these?
Must worry about contamination, often there is mixing of sediments with decomposition. Must take samples from vertical accumulations where levels are clear. We want stuff with low rates of decomposition like bogs.
Can you work your way through the pollen diagrams presented and detect changes associated with the Younger Dryas?
The time axis is shown as depth in the core. This is the law of superposition with the shallower being more recent.
Each graph represents the abundance of a pollen type over the same period. Thus if we read across we can compare the abundances of pollen extracted from a sample.
Here abundances of pollen are graphed along a vertical axis that represents time, in thousands of years BP (radiocarbon years), as many levels of the buried mud were carefully dated. Changes in abundances of 13 pollen types over time are shown. Following left to right across the graph one can see the abundances of different pollen types found in a single sample. Pollen zones have been identified on the right-hand side of the graph – these are groups of levels, or times that contain similar abundances of pollen types, thus similar past vegetation types, such as biomes.
On the right, the vertical axis groups the pollen zones that represent the same ecosystems, the same zones
What is a stadial and what is an interstadial?
A stadial is a cold period occurring within a glacial or interglacial time. The warmer time between stadials is referred to as an interstadial
How did an advance in a dating techniques enable the new finding of the Younger Dryas at Alpine Swamp, New Jersey
You can see the regional paleoecological changes on maps that reveal that at the time of the Younger Dryas, Alpine Swamp was near the transition between mixed forest and boreal forest. Such transitional areas are particularly sensitive to climate change. Thus the cooling was obvious.
How would a comet collision (or its fragments) trigger Younger Dryas
cooling? What evidence is proposed for the comet and its impacts?
The heat from the comet impact would have ignited wildfires and burned alot of biomass. This would thus create an “impact winter”, blocking sunlight from smoke and chilling the earth. This heat would destabilize the ice sheet. Evidence of this can be seen because Biomass fires release a number of chemicals into the atmosphere such as ammonium (NH4), nitrate (NO3), acetate, oxalate, and formate. The concentrations of these aerosols can be measured in cores from glacial ice thus serve as proxies for fire.
The impacts of the comet could have also collapsed ice dams which would then have allowed extensive meltwater flooding in to the Arctic and North Atlantic Oceans.
Further evidence of the impact of meteor fragments comes from increased concentrations of platinum (Pt) and other heavy metals measured in ice cores at levels that correspond to the beginning of the Younger Dryas cooling.
Wide dispersal of pollen does not mean that the species of its parents plant will laso be widely dispersed
Taxonomy is the classification of living things and Fossils can be identified to a meaningful level of taxonomic resolution.
Spruce and Birch are a part of boreal forest. A shift from deciduous to boreal forest indicates cooling.
Stadial
Interstadial
