Final Exam Review.docx

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Department
Biomedical Communications
Course Code
HSC401H5
Professor
Nicole Myers

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FINAL EXAM REVIEW SHEET Lecture 17: Geologic time Explain the difference between relative and absolute time. - relative age scale o used more often in geology  easier and cost/time effective o puts items in order relative to each other (ie. something is older/younger than something else) - numerical age scale o to put an exact date, have to use radiometric dating o expensive, time consuming, and hard to find right samples - in geology, want to put items in relative order first and then try to find exact dates Determine the relative geologic history of a region from a diagram showing the different rocks units. - look at diagram in notes Explain and apply the principles of (1) cross cutting relationships; (2) inclusions/xenoliths; (3) superposition; (4) unconformities; and (5) original horizontality. - The Principle of Cross Cutting Relationships o any feature which cuts across other rocks or features must be younger - The Principle of Inclusions/Xenoliths o any piece of rock (inclusion or xenolith) included within another rock must be older than the rock in which it is incorporated - The Principle of Superposition o the oldest layer is at the bottom and the youngest layer is at the top - The Principle of Unconformities o an unconformity is a rock interface which represents a gap in the geologic record, like pages missing from a book o ie. some period of time where erosion was occurring above sea level and no sediments were being deposited and then sea level rises and sediments are deposited - The Principle of Original Horizontality o sedimentary layers (and lava flows) are usually originally laid down horizontally o if they are not now horizontal, they have been deformed Describe how fossils can be used to assign relative age and to correlate rock records around the world. - fossils themselves don’t give exact date o occur at a specific time in earth history - through time, different fossils appear then disappear o if you find a fossil in one place and then in another place, know that the rocks are approximately equivalent in age - if you find fossils in one location, you can try to correlate them to other locations o can use fossils to compare one area to another Understand the relationship between major events in the history of life on earth and the divisions of the geologic timescale. - Precambrian: 4.5 Billion to 545 Million o contains Hadean and Archean eons - Paleozoic: 545 Million to 248 Million o Cambrian explosion - Mesozoic: 248 Million to 65 Million o Permian-Triassic extinction - Cenozoic: 65 Million to Present o when dinosaurs went extinct Describe how the amount of parent and daughter atoms changes with each half‐life. Draw or interpret a diagram showing this change and be able to calculate the age of a rock from the number of half lives that have passed. - two isotopes – parent and daughter - when crystal is formed, it will contain 100% parent and no daughter - once mineral forms, over time, parent decays forming daughter - have to measure amount of parent and daughter and compare ratio of two - for every half life, parent decays into daughter by half - if you know the half life, you know how old it is o if the ratio of the parent and daughter is 8 and 8, that is one half life o if the ratio of the parent and daughter is 12 and 4, that is two half lives - if the ratio of the parent and daughter is 14 and 2, that is three half lives Explain how the half life relates to what kind of materials is dated (e.g. age of earth from U‐238, archaeology from C‐14). - carbon 14 dating o used in archaeology quite a bit o decomposes to nitrogen 14 o had a very short half-life – 5,730 years o only good to measure 50,000 - 60,000 years ago o not used in geology because most rocks are older than this range - uranium 238 o has a very long half-life – 4.5 billions years o used in geology Explain why radiometric dating works best for igneous rocks (cooling through the blocking temperature). - works best for igneous rocks o at the lower temperature, daughters are locked into the crystals o in igneous rocks, new crystals form as the rock cools, so if you date a mineral within an igneous rock, you know it formed at the same time as the rock itself - metamorphic rocks can work too, depending on the minerals and the temperatures o at higher temperatures, the crystal loses daughters so the clock loses time Explain how dates of igneous rocks can be used to bracket the age of sedimentary rocks. - sedimentary rocks are often composed of eroded bits of other rocks o imagine a 1 billion year old granite (igneous rock) being eroded, transported, deposited and lithified into a sandstone a million years ago o if you dated minerals in the sandstone you would get an age of 1 billion years, when the sandstone only formed 1 million years ago o such information can actually be quite useful - but not for figuring out the age of the sedimentary rock Memorize the ages of the major boundaries of the geologic timescale, between the Precambrian, Paleozoic, Mesozoic and Cenozoic times. - Precambrian: 4.5 Billion to 545 Million o contains Hadean and Archean eons - Paleozoic: 545 Million to 248 Million o Cambrian explosion - Mesozoic: 248 Million to 65 Million o Permian-Triassic extinction - Cenozoic: 65 Million to Present o when dinosaurs went extinct Lecture 18: Earth History Describe the formation of the earth from dust and planetesimals, through differentiation, and finally through the formation of the moon. - after the big bang, the universe began to expand at a constant rate o the explosion caused matter to initially be distributed inhomogenously  lumpiness; wasn’t smooth o over time, lumps of denser matter became centers of high gravity and began to grow o eventually the lumps became large group of stars and eventually galaxies o large groups of stars are called galaxies - early solar system forms, with dense ball of gas at center – proto sun – with surrounding rings of gas and dust - a nebula forms from hydrogen helium and heavier elements left from the big bang - the nebula, under the influence of gravity, condenses into a swirling disc, with a central ball surrounded by rings o as it condenses, it begins to spin - ball at center grows dense and hot enough for fusion (two hydrogen atoms get together to form helium) o once fusion begins, this becomes the sun - in the rings, dust particles collide and stick together, forming planetesimals - planetesimals grow into the proto-Earth o as it continues to grow, the interior heats up and becomes soft - as the proto-Earth gets bigger, gravity reshapes it into a sphere o interior differentiates  more dense iron-nickel metal moves into core  less dense rock moves outwards into crust - soon after Earth forms, a small planet, about the size of Mars, collides with it o Earth has iron core and so did the body that collided with it o body added iron to earth and some rocky debris got sent into space - debris formed a ring around the planet o the Moon formed from the ring of debris Know when the Hadean Eon occurred and describe the structure and the conditions on the surface of the earth at that time. - 4.5 to 4.0 billion years ago - partially melted rock which were formed due to volcanic activity had eventually rifted the continents apart and split the earth into half - very hot - some water, but probably acidic - a lot of storms Know when the Archean Eon occurred and describe major events that occurred in this time, including the beginning of formation of continental crust and the development of single‐celled life. - 4.0 to 2.5 billion years ago - surface of the earth was partially molten but also partially solid - lots of volcanic activity - lots of water - surface of earth was still acidic - lots of stromatolites - most of this life originated in hot spots - probably varied quite a bit, especially when there were major impact events (like when the mars- sized body collided with earth and formed the moon... the entire surface of the earth would have been molten at that time. - no organized rifting during that time - probably water on the surface of the earth - no oxygen - continental crust first started to form – evidence (green stone belt) - there was no oxygen or water on the surface of the earth when they were formed - plates were moving faster and small fragments of continental crust with passive margin stretched apart o mostly small fragments from volcanic arcs which cld have produced basaltic volcanism were over overtime, differentiated and formed mafic and silicic minerals o as they recycled, new arcs formed on top o today, (greenbelt) they have narrow slices of volcanic rock and other rocks Describe the composition and structure of greenstone belts, and explain how they differ from modern continental crust in terms of their composition and the plate tectonics which formed them. - formation of greenstone belts o greenstone belts were formed early in the history of the earth when the earth was mostly covered by oceanic tectonic plates o where they subducted, they formed island arcs with a mafic igneous composition o these accreted together to form greenstone belts o eventually these coalesced and eventually they were "processed" further by tectonics when they partially re-melted o the processing created much more silicic/felsic (grantic) rocks when today form the continental crust o so the greenstone belts formed early in the earth's history and most were eventually converted into normal continental crust today o but in a few places the original greenstone belts survived o called greenstone belts because the mafic rock gets a greenish color when it weathers. - difference between modern continental crust and greenstone belts o greenstone belts are mostly made of mafic igneous rock like basalt, whereas modern continental crust has much more felsic/silicic igneous rock like granite Know when the Proterozoic Eon occurred. - 2.5 billion years ago to 500 million years ago Explain and sketch the six steps of the Wilson Cycle. - a continent rifts when it breaks up - as spreading continues an ocean opens, a passive margin cools, and sediments accumulate - convergence begins; an oceanic plate subducts, creating a volcanic chain at an active margin - terraine accretion-from the sedimentary wedge welds material to the continent - as two continents collide orogeny thickens the crust and building mountains - the continent erodes, thinning the crust Name and know the order in which four major supercontinents formed. - 300 Myr: Pangea - 1,300 Myr: Rodinia - 1,800 Myr: Nena - 2,500 Myr: Arctica Recognize the parts of North America that correspond to the formation of the supercontinents Arctica, Nena, Rodinia and Pangea and the breakup of Pangea. - the original North American continent, Arctica, which started to form about 2.5 billion years ago from smaller continents and was completed by about 1.9 billipon years ago when old Archean cratons were welded together by the Trans-Hudson Orogen and others - added to the North American continent during the formation of Nena about 1.8 billion years ago after the Penokean Orogeny - added during the formation of Rodinia about 1.3 billion years ago during the Grenvile Orogeny - added during the formation of Pangea about 600-300 million years ago - added after the breakup of Pangea about 250 million years ago - Canadian Shield  ARCTICA - Mazatzal and Yavapal NENA - Greenville Origin  RODINIA - Africa/S.America and Europe/N.America, Greenland, Ireland  PANGEA - Africa glued to the east coast of North America  Break up of PANGEA Understand the timing and cause of the increase in oxygen in the atmosphere. - driven by respiration of cyanobacteria o very little oxygen in the atmosphere during beginning of proterozoic o simple, single-celled organisms consumed CO2 in the atmosphere and released oxygen as a waste product o oxygen slowly built up - around 2.5 billion years ago, atmosphere began become oxidized and there was youngest BIF o banded iron formation o once oxygen started invading the atmosphere, all the iron in the ocean became oxidized Explain the formation of “banded iron formation” and why it is found only in Proterozoic rocks. - before the accumulation of oxygen in the atmosphere, iron was able to exist in seawater - when oxygen levels increased, however, the iron bonded with oxygen (it oxidized, or rusted basically) and sank to the bottom of the ocean to form banded iron formation - ever since that time, any free iron that exists quickly reacts with oxygen and rusts - can only occur in proterozoic rocks o formed as soon as oxygen levels increased in the Proterozoic o then all the iron, or the vast majority of it, was used up o no more BIF was able to form Describe the evidence for global glaciation in the late Proterozoic. - 750-580 Ma - widespread glaciations o glacial deposits found on all continents o for them to be found at equatorial regions, this implies that it must have been cold all over the planet Explain how the hypothesized cause of the snowball earth, including CO2 depletion by weathering and reflection of incoming solar energy from growing ice during the runaway cooling phase, and CO2 increase from volcanic emissions and the absorption of solar energy in emerging seawater during the runaway greenhouse phase. - runaway cooling phase o around 770 million years ago, supercontinent Rodinia was breaking up  resulted small continents near the equator and caused shallow seas all around the world o formerly landlocked areas are closer to the ocean and undergo more erosion/weathering  weathering is a chemical reaction that takes C2 out of the atmosphere o a lot of erosion reduces levels of2CO , a natural green house gas o reducing CO2causes global temperatures to fall which results in sea ice formation o sea ice reflects incoming heat energy from the sun, temperatures fall even more o whole process results in runaway cooling  positive feedback  more reflection causes more ice which causes more reflection etc. - runaway greenhouse effect o volcanoes emit CO 2 which builds back up in the atmosphere o normally the ocean absorbs excess CO 2 but since the oceans are frozen, levels get much higher than normal o results in runaway greenhouse effect  temperatures get higher and melts sea ice  as more sea ice is melted, more heat is absorbed and the temperatures continue to get warmer Describe the Phanerozoic (Paleozoic, Mesozoic and Cenozoic) evolution of North America in terms of the east coast (from passive margin to subduction and accretion to continental collision to rifting and back to passive margin) and the west coast (passive margin to subduction and accretion). - during the Phanerozoic the east coast began as a passive margin (after the breakup of Rodinia), then became a subduction and eventually collision zone when the plates started converging again to form Pangaea o then it became rift and then a passive margin again when Pangaea broke up - meanwhile, on the west coast, first we had a passive margin, but subduction has been occurring for some time there o at various times, terranes have been accreted onto the west coast, causing some mountains to grow Describe and place on a map the location of major active mountain ranges on Earth today. - Alpine Himalayan chain o where Africa and Europe are colliding in the Mediterranean o Arabian and Eurasia are colliding in Turkey and Iran o India and Asia are colliding in the Himalaya - along the west coasts of North and South America o subduction of the pacific (and other) plate is occurring Lecture 19: Rivers Define drainage basin and recognize the major drainage basins in North America. - drainage basin o the area drained by a stream and its smaller streams (tributaries) - five major drainage basins in North America o Arctic Ocean o Hudson Bay (into Arctic Ocean) o Atlantic Ocean (via Lake Ontario to St. Lawrence Sea Way to Montreal) o Gulf of Mexico (via Mississippi River) o Pacific Ocean (via Great Basin) Describe how stream gradient (slope) and channel cross‐sectional profile changes from the headwaters to the mouth of a stream. - rivers start off steeper and become shallower up until mouth of river - in northern parts of river, there is a V-shaped cross section but it becomes U-shaped with distance - rivers get less steep, shallower, and wider, flood plains get wider Know and apply the formula for calculating river discharge. 3 - discharge (m /s) = width (m) x depth (m) x velocity (m/s) - discharge = area of opening x rate of flow Explain the process of waterfall retreat. - water is running over a very resistant rock o lockport dolomite - water is pounding the rocks below it - rocks below are quite a bit softer and they get eroded away - eventually it undermines the strong unit at the top and it collapses - waterfall retreats and the process starts all over again Describe how material is transported by a river (as bedload, suspended load or dissolved load) and explain how discharge controls how much material is transported (e.g. higher discharge = more transport and erosion). - increased discharge o more transport and erosion o the faster the water is moving, more material and larger material can be transported - decreased discharge o less transport and more deposition o the slower the water is moving, less material and smaller material can be transported - the finer the material (ie. silt and mud) the easier it is to transport - the coarser the material (ie. sand) the more energy it requires to transport - if really coarse material (ie. gravel or boulders) it takes a lot of energy to transport - in a river, there are three different types of transport o suspended load  finer grained stuff (ie. silt and mud) that stay suspended in the water by turbulence o bed load  larger things (ie. sand grains, cobbles, and boulders) that move along the bottom via sliding, rolling or saltation (hopping action) o dissolved load  stuff that can’t be seen that has been dissolved in the water (ie. ions) Describe characteristics of meandering versus braided rivers and explain the factors which control the formation of each. - braided channel o several little channels that braid in and out of each other o form when there is a lot of sediment and a lot of water o usually devoid of vegetation because channels are constantly shifting and wiping out vegetation o occur where there is an overload of sediment and the river is choked up - meandering river o single channel formed when the moving water in a stream swings from side to side eroding the outer banks and widening its valley o occurs where banks of the river are vegetated and there's a reasonable balance between erosion and deposition o alternatively erodes sediments from the outside of a bend and deposits them on the inside o less transport in these kinds of rivers o velocity changes based on where you are in the channel have maximum velocity o maximum velocity swings wide Explain and sketch the pattern of erosion and deposition in a meandering channel, its relationship to the stream velocity, and how this pattern can result in the formation of oxbow lakes and cutoffs. - single channel formed when the moving water in a stream swings from side to side eroding the outer banks and widening its valley - occurs where banks of the river are vegetated and there's a reasonable balance between erosion and deposition - alternatively erodes sediments from the outside of a bend and deposits them on the inside - less transport in these kinds of rivers - velocity changes based on where you are in the channel have maximum velocity - maximum velocity swings wide - cut bank o outer edge of a curve - point bars o inner edge of the curve where sediment accumulates - meander neck o narrow isthmus of land that separates tow meanders that are cut toward each other - cut off o occurs when erosion eats through a meander neck and there is a straight reach of the river - oxbow lake o a lake that is separated from the river as a result of erosion Describe the shape of deltas, the shape and location of natural levees, and the process of “lobe switching” and explain how each is the result of river deposition. - river is moving along and it comes into contact with a body of standing water (ie. ocean or lake) forcing it to slow down - as it slows down, not a lot of sediments are able to be transported o stuff that was in suspension rain down and settle on the bottom o stuff that was bed load stopped moving - delta o at the end of a river where all the sediment gets dumped - natural levees o form on either side of the channel o when a river floods over its banks, the water spreads out, slows down, and deposits its load of sediment o over time, the river’s banks are built up above the level of the rest of the flood plain o resulting ridges are called natural levees o happens where river meanders - lobe switching in the Mississippi Delta o when there is too much sediment, the river finds another place to deposit sediment, thus creating a new lobe; too much bedload blocking a river so the river takes a different path Lecture 20: Groundwater Define porosity and permeability and know relative values of
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