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POLC66H3 - Lecture 1-

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R Rice

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Economic Geology: Rocky resources/mining in Canada 4/11/2013 5:36:00 AM Economic Geology – brings a lot of people into Geology.. Companies look for people that look for training (differentiation between rocks and minerals) – logging core.  drillers go and take long drills of rock, and you must tell them what it is. The Geology of Ontario – 4 layers (from Toronto Rocks by Eyles) Layer Cake Diagram (see slide) 4 layers of Ontario Geology in it. The oldest layer is the one at the bottom, Layer 1- that layer in Ontario is more than a billion years old. Precambrian and aged – comes from plate collision and mountains. Most rocks are metamorphic rocks. Metamorphic rocks in this stage; made when old boundaries existed – old plates existed and formed old mountains in that area. (GNEISS – roots of an old mountain that no longer exists – mountain has been worn away by erosion) Layer 2 – Tropical Seas Paleozoic – hot and tropical; near the equator; however, over time the erosion wore it down to relatively flat. Peneplenation – there was a rugged surface and it got worn down almost flat – it was being eroded by all those elements. Coral reefs started to flourish – so we already know coral reefs make a rock called (sedimentary rock) – limestone. Layer 2 has lots of limestone. It also has other sedimentary rocks. Totally different from Layer 1 – lots of Limestones, but also has (coral reef needs a lot of light) if there isn‟t, coral reef dies out, and you produce KLASTIC sedimentary rocks – Sandstone, shale, etc. Interbedding – layer of limestone, layer of clastics, layer of limestone, etc. Repeated cycles of rock types – in this case clastics, and non clastics. Because of changes in the environment. Thick black line – surface of erosion – the great unconformity – missing time in the geologic record!! Black line between blue and yellow – the BIG GAP – another unconformity… more missing time in the geologic record. For a while, layer 2 was the surface, so the sedimentary rocks wwere the surface for a long time, getting eroded. They were on top. Eventually something else got deposited on top (the yellow stuff) all that yellow stuff represents is what Toronto area is really famous for (glacial and interglacial sediments – NOT ROCKS) Layer 3 – covered by a KM or more of ICE – 20,000 of ice. We are at an interglacial time right now (between times of ice cover) We are going to talk about the economic geology – in terms of the various layers. .. Layer 1 is different than Layer 2 and Layer 3 is different. History – First geologic map produced for King Ramses to find Gold –Gold mining district in Eastern Sahara. IT was written on papyrus, amazing that it lasted for this long – valley of mini baths. This is the area – Mediterranean Sea and the Red Sea on the eastern side. Pink = layer 1, and Brown and Green = Layer 2, and White = Layer 3 The reason for the map, was to find way back to the Gold resource. Beckenstone – ornamental stone and the Ancient Egyptians prized it as an ornamental stone. Before Georgius Agricola – people thought minerals had magical properties, thought that rocks and minerals were dragons tears, they were alive, living things, all sorts of properties were ascribed. Georgius Agricola – he was an observer – he liked to go out and spend time looking and observing. He was lucky enough to live in Germany – it was an area that had silver mines; lived on the property of one who had one of the best silver mines. Geology – he wrote a book that talked about not only his thoughts about geology of the area and mines – but about the diseases slaves got in the mine…he was way ahead of his time – it wasn't appreciated at that time, it was a handbook of those working in the industry – it was appreciated long after his death. Bring a scientific approach to geologic resources. William Strata Smith – canal engineer in Britain = principal of using fossils – to figure out with layer is older. In 1815, he made a geologic map (first map of Britain) = father of stratigraphy (study of layers) or father of modern geology – this map changed the world the way people study geology. He really thought about how the rocks relate to one another, he actually showed what was below the surface not just what was above the surface. Sir William Logan – task it was to find coal.. for upper and lower Canada – Ontario and Quebec. Looking to find coal, and there wasn't coal to be had – so he made a map of Canada and found coal in the eastern provinces – particularly in Nova Scotia. Needed coal to build railway – Sponsored by Molson Canadian – and Sir William Logan and his map and his search for coal were directly responsible for confederation – including eastern provinces of what we now call Canada! Inuit Mining – 2000 years old rocks – oil lamps (Newfoundland) (see slide) – Green Areas – are part of Layer 1, some of the oldest crust that we have in Canada. “greenstone” Metamorphic Rock – Greenstone If you have an area of Greenstone – it's a great place to search for resources such as Gold. Really old areas of the crust from really old collisions – excellent places to search for Gold. VMS – Volcangenic Mass Sulfides (short answer question) - you get seawater, and near to the mid ocean ridge, that sea water gets into the cracks – and, it gets heated up, as that water gets heated, and goes through the rocks, it ends up exchanging oxygen, potassium, calcium sulfate, magnesium, between water and the rock – sometimes its losing to the rock, and gaining things from the rock – as it gets really really hot, it picks up IRON, SULFUR, ZINC, and COPPER. Because water is hot, its able to hold on to those things, eventually the water makes its way out of the rocks, comes back out into the cold sea… Its temperature cools down, and can no longer hold on to those copper, zinc, etc and precipitate out as minerals. Lucky place to be when mining for minerals. Sulfide minerals made from these elements are basically pure. If you get down their and retrieve them, you can scoop them in, and put in container, no refining to do. Worth lots of money – volcagenic mass sulfides – form near the MOR. Layer 1 formed from old collision, so lots of old oceans were closed to form Layer 1, (recycled as continents came together to form Layer1) , and when you close an ocean, you end up scraping some of the oceanic crust between those two continents.. and its often the mid oceanic ridge part that gets saved (buoyant and youngest). So in Layer 1, there are areas where you actually have some volcanogenic massive sulphides, and that's why Layer 1 is so rich in sulfide minerals in some area. Sulphide Minerals can cause problems – if they are just sitting there weathered, they can cause problems. If people are mining them, there is more problems. Acid mine Drainage – acid mine drainage can cause serious problems for clean up, for other water bodies. Example in BC, Acid Mine Drainage – rusty looking streams – the run off cme down the hill, and into the water. If you are an aquatic critter (fish, or other living creature) you have tolerance range, for how much acidity it can thrive in, and it can even live in. If you put enough acidity in, everything will die, or wont thrive. This can be a serious problem. So they had to do a major clean up at this mine (closed in 1974.) Benefits to the rusty look of sulphides: if you have a sharp eye, and GOSSAN – the soil will look.. from rusting these sulphide minerals, so if you do have sulphide minerals in the area, the soil can reflect that. IN this case, its showing that sulphide minerals are coming from Plutons (igneous intrusions) – weathered away, but still shows rusty look to the soil. Sometimes, you will see change in vegetation, vegetation cant survive in different soil types. No Midocean ridge here, but igneous intrusion coming in the area and it has sulphides … BIF – short answer question – Banded Iron Formation - records the oxygenation of the atmosphere… - lots of iron around before this time, however it didn't rust, because there was no free oxygen in the atmosphere. At the time BIFs were forming, the atmosphere was oxygenated through photosynthesis, and it formed nice thick layers of BIF. 90% of iron from steel, is taken from BIFs. That BIF should be flat, but its standing on its end.. getting ready for shipping. Iron rusts, and rains, it doesn't just fall to the ocean, it gets remobilized by these turbidity currents.. underwater landslides…they are sediment rich currents moving under water by gravity, flowing down slope. These are dropping off material they picked up, and taking it deeper out into the oceans, and they are making that graded bedding. So you get larger grains at the bottom, and small grains at the top. Rusted iron is building up in layers at the bottom, forming these BIFs. Formed 2 billion years ago….2 GA. Layer 1 – this is the way the Subdury Impact Crater looks. Shortly after BIFs were born, a meteorite slammed into the earth- so hard, so much pressure, ti actually liquefied some rocks. The Rock that's liquefied is shown in Green – it becomes igneous – wasn't heat it was pressure thing. IT became molten rock. Its lucky for Sudbury, because in that igneous complex, a lot of economic minerals are quite concentrated. Plate Tectonics Compression – erogenous happening, compressed. IT used to be circular, now its got a long access from upper right to later left. During Erogenies that happen after the meteorite hit. As I said, so much pressure it liquefied rock – ORE: it means a body of mineral that is rich enough in concentration, that its economically worth mining. If your going to make money from mining it, you might as well. Chalcopyrite: the ore they are looking for. Sudbury, has so many mines for nickel not because people are interestd in having nickel, but because of World War 1. They needed armour to protect them. Steel plates to protect the boats. It was at Sudbury – so it became a famous place for mining nickels. Layer 2: second Layer of Rocks (Sedimentary Layer) -We are now talking about soft rocks, sedimentary - These colorful blotches are showing us different places in NA where you can find coal…Best type of coal is limegreen stuff in the picture, or actually sorry the yellow (anthracite) – coal spread out much across the United States and Western Canada – much of Canada doesn't have coal. Example of Coal Mine – BC & Alberta  This is a surface mine makes a big mess  Will not miss the Mine  They had to strip area of trees to mine – clear cut…  First commercial mine opened in 1720  Springhill Disaster 1981, 121 boys and men died in the mine, there was an explosion. So they formed a labour union to prevent that from happening again.  Layer 2 = oils. Oil Sands of Alberta – is a layer 2 resource.  Canada has more oils than Saudi Arabia, however the problem is in Canada the oil is stuck to the sand, that's why they call it heavy oil nd stuck to sand – means it difficult to obtain the oil. Canada is 2 only to Venezuela Heavy Oil reserves.  If you have ever been to Southern Shores of Georgian Bay – Craigleth Shale Oils – oils occur in Shale.. Shale is Sedimentary. So the shale is a fine grain sedimentary rocks, and oil is in it. Didn't make it for long, and then they saw free flowing oil other places and stopped this.  The first commercial oil well found in Southwestern Ontario in 1858. Reservoir – Storage Tank (a natural storage tank for Oil and Gas) Boiling gas buried, and it wants to go out, its less dense that the rock, and it will raise through. Rises to the blue layer, and it cant rise anymore, because layer above it is impermeable to oil and gas. The oil and gas will travel up as far as it can, encounters the impermeable layer, and cant go past, and the rocks collapse. The driller will go down there, and you can collect oil and glass. You don't have to draw these , but it will come up as a multiple choice. Impermeable Layer – trap rock – prevent them from going up. The trap rock is keeping it from going up. There is oil shown in black, and natural gas in the top. Natural gases are less dense than the oil. Production in Canada and US – Alberta makes the far share of oil in Canada, makes lots of money! How is oil taken out of ground? Cant just taking it out (or else you collapse the ground) Drill three wells, well to pump the oil form, and two other wells to pump material. The entire state of Florida would sit inside the Oil Sands. Heavy Oil will have a larger environmental impact than conventional oil. “Room and Pillar” – Salt – look at the size of those trucks – these are pillars of salt. Salts are left behind because they cant evaporate with the water. Layer 3: So, this is sort of between the line of Layer 2 and 3, because they were deposited 150 million year ago, but wouldn't even know if they were there, if it wasn't for Layer 3 processes, so what happen is when NA travelled over a bunch of hotspots (like Islands of Hawaii) 4 hot spots – producing these kimberlite pipes.  over time NA past over 4 different mantle plumes – ice has been covering NA for quite a while – when ice comes from North to the South, it scrapes the rock – scraped the kimberlite pipes, and brought material to the south. It brought Kimberlite material that contains diamonds – diamond bearing material to the South. Now we have diamond mines in Canada – so that people can go mining – looking for diamonds. Canadian Diamonds – have a polar bear on it. Diavik Mine – open pit mines – working on Kimberlite Pipes – 200 Million years ago, when Pangea began to break up. Running over mantle plumes right over the continents making these deposits of kimberlite pipes. Lots of pipes have diamonds in them. If you find a kimberlite pipe you are quite lucky. Pathways – of some of those hotspots tracks – the ages on them , The diamond shaped dots are wear diamonds are found. Haileybury, New Liskeard Kimberlite – Igneous Rock; Looks like a carrot – a giant carrot under the ground (kimberlite pipe) tighter deeper down, as pressure comes, less and less, and there is less pressure at the surface. It looks carrot shaped! This one would continue on quite a bit deeper than it is, and get thinner as it went down into the ground. There is glacier material on top of the pipes – so people wouldn't have found them, if some of the materiail hadn‟t been brought to the south – because they are covered with glacial materials – how they look for them? Fly with planes that have magnatometers – these will look for differences in the magnetic character of the rocks, kimberlite pipes register as quite magnetic… highly magnetic and you will see these magnetic circle shapes above. You get pretty excited, and you lay claims on that area – although its under ice, you can find them using these geologic equipment. Ice leaves a trail when it travels, it leaves records behind. Sometimes these records are called as ESCOR – a little river under the ice – when its flowing fast – it can carry large sediments – even pebbles, cobbles, moving quickly lots of energy (underneath the ice) HOWEVER, when there is less energy – like ice is melting, or disappearing, eventually the under the ice river, wont have energy to carry those sediments and it drops them unceremoniously, whats left behind is a big snake – 100s of km long, of big sediments like sand and gravel – escor – its theses that have the diamonds in them from the ice scraping over the kimberlite pipes – they tested the escar upstream from where the ice came from, until they found the source, found in the green stop signs here. This is where Layer 3 – the ESCAR< was able to help find older resources – kimberlite pipes are between layer 2 and 3. So officially beginning Layer 3 – resources are coming FROM layer 3 – Ice sheets – placer minerals – so placer minerals are brought form elsewhere – they are talking about Gold – gold that's found around a river. You can do it really cheap with a pan – and sit and shake till you find gold, very cheap but labour extensive – you can dredge out huge areas of water instead – and see If theres gold to be have, Klondike Gold Rush (12 million ounces of Gold) Ore Deposits Deposit of Mineral – an Ore Body – its more of a money thing! Its only a ore body, if its economic worth mining it. So it could be an ore body today. Ore is about financial considerations. How much of a mineral there is within a body of rock. If you have a high concentration of Gold today, its worth mining at any price. An ore body is a body of mineral – and its only defined such if its worth going after in an economic senses. Plate Tectonics – Ore is related to plate techtonics. The different metals in different locations have to do with plate tectonic situation of now or in the past. Magmatic Arc  Island Arc  different metals here than other places. Oceanic crust  made up of different ore metal deposits. At different places  different metals. Hydrothermal Ore Deposits: water gets heated up, so groundwater gets heated up by a magma source  when that water gets heated it up, it moves through the rocks, when its really hot it leeches or steals elements form the rocks around it. It cools down, and the elements come out and are deposited. Magmatic Ore Deposits: Basaltic Magma – A magma chamber and in that chamber you have a really hot basaltic type magma – over time.. if that magma doesn't exit the magma chamber by eruption, its just going to be sitting there, it will start to cool down. As it does, minerals crystallize out. Every mineral has a certain temperature at which it cant be liquid anymore, if it gets cool enough it will get solid. If you heat up the rock – it wont remain solid it will become liquid. The magma chamber, the temperature is going down, and certain minerals are coming out – crystaliizing – forming solids. 1.) They could float (rare) 2.) they could sink. They will form layers at the bottom. 3.) Crystalize on the walls. The second is important, because that's where people tend to be interested in , (chromite – pure layers are economically advantageous) Bowen‟s Reaction Series - If its realy hot you start at the top –(primitive magma) as it starts to cool, the first minerals to come out is Olvine, Pyromomine. It will continue getting cooler, so you will get Pyroxenes as solids, and they will have more sodium in them as it cools. You will get Amphiboles, and felspars will become more sodium rich – Biotite MIKA – this is what happens when it cools. No calcium and more sodium. When you keep cooling – you will get a well developed magma potassium Feldspars, and Quartz. If you have a bucket full of basaltic magma, and everytime the crystals come out as solids, they get removed from the liquid. Its losing calcium, as it comes out (the solid crystals) – the building blocks are being lost and taken out of the magma, whats left in magma is different that what you started with. Your left with silica, potassium feldspars, sodium, lighter things. Sedimentary Ore Deposits Many types! An evaporate deposit – you‟ve seen it before – you have, shallow salty water. In that, the water will evaporate away if its dry enough, but salts can go anywhere – increasing concentration in salts – they become brine. Placer Ore Deposit: If you like watching reality tv, you might like Gold Rush Alaska. People go to remote locations to find land that either has currently or previously had rivers flowing through it, is because sometimes rivers can transport Gold from elsewhere. Curves – Big Rivers, if you are not rich yourself you can go there with a pan – with mesh, and you can shake out fine grains – to find gold. The placer minerals were originally found somewhere else, and found in riveres, because they were replaced by water. Residual Ore Deposits: mostly in tropics; really great aluminum! You have rock grading up into soil, over a long period of time weathering happens to that soil, so all the good nutrients from it gets leeched out, and it takes out elements that would be used for growing plants. But it leaves behind aluminum. Lecture 7 4/11/2013 5:36:00 AM Lecture 7: Geologic Time, Fossils, and Evolution Plate Tectonics is still examinable! So forget about everything else, and study plate tectonics. Weathering and Erosion is cancelled. Geologic Time is the toughest concepts; people who exist in such a small bit of time to imagine how long the earth or even the universe has been in existence. We are an absolute blink of the eye. Read Chapter 9 – The earth is 4.56 Billion Years old 4,560 Million. Stratigraphy – study of rock layers (sedimentary rock) Relative Age of Rocks – will be on the test! th In the 11 century, a Persion fellow, Avichana, looked at mountains and didn't think that mountains had always been there. He thought they were built along a series of events. Deep Time/ Geologic Time: Many people thought that the Earth was relatively young, but Sham Qu believed the earth was unimaginably old. Ancient Greeks, looked in the mountains at the layers of rocks, and the fossils and they noticed that the fossils were marine fossils. Fossils from the oceans – difficult to explain, but these fossils were found on top of mountains. In the West, a lot of ideas about time (how old the earth is, how it was created) heavily based in the Christian Religion. The Christian church taught that the earth was created in 7 days, and climate is fixed. The earth looks how its always looked. People found sediments – contributed to the Noah‟s flood. Archbishop Ussher of Island – calculated the Earth to be 5600 years old – after study of the Bible. Some people calculated date and time after study of the old Testament. Catastrophism - Earth stays the same, but every now and then you have a huge disaster - huge eruption, violent event – affect a huge part of the world, and changes things. Biblical flood – (noah‟s flood)! This was the prevalent theory in the West for quite some time. James Hutton – need to remember for the finals. Found rocks that were not flat, but rather the rocks on the bottom were tilted. Why were the rocks at the top flat? New theory – UNCONFORMITY - James Hutton noticed something else – GRANITE (continental crust), I think Granite is a rock that cooled from molten magma. A lot of people thought rocks came from the water, but GRANITE looks like it was cooled from magma, so he thought it didn't come from the water. He came to that conclusion after doing research on granite. Hutton’s Idea was in conflict with Catastrophism: Uniformitarianism – all these things we see happening today, rivers moving sand down the stream, ice moving sediments out of the mountains – these things must have happened in the past as well. So he said, the earth hasn't always been exactly the same, but all these changes have happened all the time – constant changes. Constant changes – small changes altering the earth. Uniformitarianism – the present is the key to the past – whats happening today was also happening in the past. Diluvialism – those people who were saying the sediments are coming from the flood, you can calculate back from the Old testament – these were all in conflict with Hutton’s idea. The Earth must be unimaginably old Cannot be 4600 years old, but much more older than that. Hutton went against the Christian church. He had a big supporter, Charles Darwin (evolutionist). th Huge debate going on = 19 century – huge debate between people like Hutton and Darwin vs. Church Theorists, and those who believed in Diluvianism, Creationism, and Catastrophism Hutton’s rocks (see slide) - he studied rocks to see why people thought they changed by one event (catastrophism) – he came up with an idea – he said it wasn't one event, instead 1. He drew flat lying rocks (sedimentary rocks start out flat), 2. Deformity - Then these rocks got deformed cause of pressure (squishing the layers), causing folds. 3. Erosion – removal of some of the top parts (by ice, wind, water) New sedimentary rocks deposited – nice and flat like all layers. 4. Whole thing is uplifted – and that's how it looked like. This time, you could not test how old rocks are – he could not find out if he was right or not, and now you can test how old rocks are. This slide starts off with the relative age of rocks – Relative Age Dating – cant say HOW old exactly, but can say one is older than the other. John Playfair (sketch on slide) Deep Time Concept – he drew this pencil sketch and at the bottom he had the “Primary Strata” the older rocks; where he saw these rocks were deformed and at an angle, weren‟t flat. There was unconformity, and then the secondary strata – flat lying sedimentary rocks. What is an unconformity? If I ripped out a chapter from your textbook, and closed the book. What happens? Its still a textbook, but missing a page… it's a GAP IN A GEOLOGIC RECORD! No hole in the ground – its just some rocks are missing… no rocks in that area.. that should be there. Picture #3: The Erosion – is important because it shows you an unconformity surface – you had rocks there but you eroded them away and put new rocks on top later, that are going to be younger. Million of years age difference between rocks – you can be losing a huge gap of age in rocks that are sitting one on top of each other. Unconformity – missing chapter in your geologic record. We have these in Ontario. (See picture 9.3) Marmora, ON – mining for iron rich rocks (red ones at the bottom) The Great Unconformity in Ontario – Marmora, ON Precambrian Rocks – Rich Iron Rocks at the bottom (Ga – a billion years old) Paleozoic Rocks: Younger rocks right on top (MA – 450 Million years old) No record of the rocks from the ages in between. These rocks eroded away Why Unconformity – lost record from EROSION, or no Rocks were Deposited. These are always found between Layer 1 and Layer 2. Angular Unconformity – Same as Huttons because the rocks he saw were on an angle, from the rocks on top. This was a “great unconformity” too because the rocks are missing between Layer 1 and 2. Charles Lyell – the friend of Hutton – he sketched Granite. Charles Lyell did more field work, and found lots of areas were igneous origins of granite was very obvious. He said there was limestone rock, then hot magma intruded in, and it was able to inject itself in between the layers of limestone. Proving that it was liquid – the granite was once liquid when it was formed. He supported Hutton‟s theory of liquoud igneous origins of granite. Scotland – Many were working in Scotland – Industrial Revolution is happening; there was a huge demand for resources – they needed metals, coal, all sorts of resources which means they need geologists – Geologists became useful. In Canada, people wanted to build the railroad – they wanted to build a railway from coast to coast – to what we call Canada now. There was a definite need for coal. There was much work in Quebec and Ontario – Geologic Survey of Canada: Sir William Logan (director) he was put In place to find coal to build railways and other industrial things. He did find coal in Eastern Provinces (Maritimes : Nova Scotia), as he was mapping Canada, there was rich deposits of coal here. Plan was attached to invite the East provinces to join the new Confederation of Canada – but because they were interested in having the coal – the eastern provinces did join. Coal Seam – tree trunks in the coal in tact with the layers of coal which proves how the layer of coal was formed. 9.5 – Fossils Body Fossil – fossilized bones or shells Fossilized Footprints, Trace Fossils – indirect evidence, not a body part, but fossilizing the footprints an animal left, or a burrow that a creature lived. Coproliths – fossilized crap, dung. Its extremely rare to fozzilize tissues or soft body parts. The instances that can fossilize these soft body parts is with permafrost (mammoths getting cost in permafrost) Sometimes jewelry pieces have bugs inside them, Amber. The key to getting a nice fossil, is getting one with finely grained sediments. If you wanted to make a mask of your face with nice mud. Or clay sized particles and water. Which will make a better mask. Mud or Sand? Mud will have a detailed face. The finer the grain size, the better the details in the fossil. Fossils are super important for relative age dating. If I were to tell you that rock is older than this rock, then fossils will help. Things wont live forever, if you find the creature, you can say these rocks are the same age as the fossil found within them. Approximately same age, since same fossil in them. Complete sequence of layers you can find in a large area (see slide) usually you ge a few here, and a few there – make do with what you have. You can use that information to say how old the layers are at each of the various places by matching up the fossils. If you always find a fossil in the pink layer above the orange layer, anywhere in Ontario, you can say the pink layer is younger than the orange layer than the pink layer is always Younger. The younger layer will always be on top. IT will help us enable to understand how old the other layers are, if we know how old the pink and orange layers are. Index Fossils: The best index fossils are short lived. Why? You need a creature that didn't live for very long to make it useful for figuring out how old a rock is. You also need it to have lived over a large area – if it only lived in one pond for a very long time its not useful, a creature that lived over a wide geographic range. Index Fossils need a wide geographic range – they need to have lived around the world, and geologic rance – how long they have lived for. (multiple choice) Law of Funnel Succession – you can use fossils to tell you how old the layers are in relative to one another. Volcanic Ash can be age- dated – which means we can say anything below the volcanic ash is older, and above is younger. We cannot put number on the layers above or below, but you know which is younger and older. Geologic Time – (diagram) Rules or Law of Stratigraphy (law of funnel succession, the stuff on top is younger) The Law of Cross Cutting: If something cuts across something else, the thing that's doing the cutting must be younger – if you are cutting something, the other thing must have existed first (hair cutting – hair existed first) if I am going to be the black line going straight up the line, the other rocks must have existed first for me to cut across them. 9.1, 9.12, 9.13 – Angular Unconformity The Sea (water body) waiting for sediments to come “subsidence of crust” _- subsidence = sinking, accommodation = room for sediments to come settle. Rivers come and bring the sediments into the body of water, and over time, layers and layers of sediments pile up, and look like the next image. They are flat sediments! They are laid down nice and flat over a very large area this is called = law of continuity = continuous over large area. After that, sediments in those layers, an igneous intrusion comes in, (hot magma comes in)- you can tell me that the magma comes in, it must be younger because its cutting across layers that already existed. Look around the edges, it is baked (the sedimentary rock) contact metamorphism (so hot the magma, it bakes the rocks around the edges) Two clues: One that cuts across it, and the baking. Then it gets tilted. The large forces happen to the whole area – causing the big folds/rocks can fold if they are buried nice and deep which made them tilt. Creates an unconformity surface – erosional surface. After that, you still have water in your sea, and rivers still coming in, so more sediments piling up. They are at an angle to the older ones. The older ones have been folded and eroded. Now we have a nice new flat layer being deposited on top. T Dikes: igneous thing, magma injected into the area that cuts across the layers from before. The dike is the youngest thing then the things around it. Because it cuts across the tilt rocks, and the older magma, and the sedimentary rock. Therefore, it must be the youngest thing. The End Result of all of this… 9.8 - Geologic Time Scale – no numbers were on it before. Built up piece by piece by information all over the world, so geologists can communicate with each other about time. IT is easier to remember a series of words; once you hear them a few times its easy to remember. There is the modern geologic time scale. The scale is exaggerated - Precambrian takes the vast period of time (on earth). WW1 = 1907 – figured out metric age dating. Arthur Holmes – putting number to rocks – he figured out how to take ISOTOPES (radioactive that occurred naturally in the rocks) and use them to calculate the age of the rock. Published his book in 1913 – Absolute Age – exactly how old something is in numbers. Before Holmes, lots of physicists and geologists trying to figure out how old is the Earth. Geologists are very old, and physicists say that it wasn't that old. Radioactive decay wasn't known… so they had not done their work on radioactivity or radioactive decay. More heat was generated inside the planet. How much time it had taken for the earth to cool.. it was missing from their calculations. … natural radioactive decay happening in the earth, makes cooling longer (adding heat all the time) so earth is a lot older. Henri Becquerel = discovered Radioactivity – made people think about how old the earth is. Rutherford – giving talk about the atom and the age of the earth. He disagreed with Lord Calvin… Radioactivity – ages in a specific way and is predictable so you can use it to tell how old something is – some of the oldest rocks on earth, are on the range of 4 billion years old – nothing much older than that, because it was molten – it was too hot. Carbon 14  Nitrogen 14 (half life of 5730 years) If I put 100 Carbon 14s, 50 will have decayed to Nitrogen 14 into 5730 years. Uranium 238  Lead 206 (half life of 4.5 billion years) So by 4.5 billion years, half of the uranium will become lead. Different types of age dating – so they have agreement among years. Its not as simple as it sounds from Uranium to Lead, but there are so many steps in between. Isotope – same # of protons but different # of neutrons. Many are unstable. “daugters and parents” - you start off with parents, and decay with daughters. After one half life, you have 50 parents left, and the other half turns into daughters, after another half life, you have 25 parents left, and 75 daughters. Exact Number : Radiocarbon Age Dating – for stuff that's not really old, and has carbon in it. great for dead sea scrolls, human remains, trees, (living organisms) some can date back 75,000 years. Figure (CN TOWER) on the slide – hard time conceptualizing Geologic Time Most of geologic time is PrecambrianTime Shows Unconformity – the big gap Here’s what we need to know… Numbers circled in red (SEE SLIDE) – Eon – Era - Period 4,600 = 4.6 billion years ago… Grey rocks at the bottom is Layer 1 – it exists beneath our feet, if we dug down far enough we will get to Layer 1 Rocks. They are Precambrian in age; so they are generally more than a billion years old… GNEISS – Medisedimentary – these rocks were subjected to a lot of pressure, because GNEISS is hardly medimorphosed, metal sedimentary rocks squished within them – basement rocks! Black line – Erosion Surface – Great Unconformity (on top of Layer 1) We are looking at a cross section across Ontario – from London to Kingston. Key Steps to Evolution of the Planet Hadean Eon ( Hell on Earth) - 4.560 to 4, 400 million years ago Horrible place to live – surface was molton, and the earliest stage of the Hadeon there was no core, mantle or a crust, it was a homogenous state… same throughout. What happen was, the heavy stuff sank, iron and nickel sank and became the core. The light stuff stuff floated to the top and became the crust (silica) This process is called differentiation or the iron catastrophe No atmosphere, no oceans – earth was bombarded by meteorites, no magnetic field to protect us, no atmosphere to protect us. Until the Iron Catastrophe happen, liquid outer core gives us the atmosphere – with convection, and protects us from meteorites . THE MOST IMPORTANT EVENT = iron catastrophe Archean Eon (4, 400 to 2,500 Million Years old) Continental Crust Its preserved in Canada Earliest bacteria existing by 3.8 million years ago – anaerobic Proterozoic Eon (2,500 to 545 Million Years ago) photosynthesizers – oxygenated the atmosphere BIFF – banded iron formation – when atmosphere become oxygenated iron started to rust – free oxygen in atmosphere, iron became to rust – fall out into the bottom of the oceans, and was deposited as pure iron minerals at Banded Iron Formation. Phanerozoic Eon (545 million years ago to today) Visible life Lots of extinction Mass Extinctions Global cooling, meteor impacts, volcanic eruptions Bigger animals survive better After extinction, lots of new species evolve Questions Compare and contrast the two main theories of dinosaur extinction Discuss the contributions of three key players to the development of the Western Theory of Geologic Time Compare and Contrast relative and absolute age dating Lecture 9 4/11/2013 5:36:00 AM The very most important thing happened ever on evolution of life on earth is “differentiation” – when our planet first started out – Haedean or Precambrain, the earth was Homogenous “same throughout” at that point, it didn't have a crust, mantle or a core. No layers; no magnetic field. Meteorites bombarding it, it was constantly under attack of solar winds – it would blow off any gases coming out of the planet – so no atmosphere – pretty hard to evolve live on earth if there is no atmosphere. Haedean – „the great iron catastrophe‟ – differentiation – heavy stuff like iron and nickel sank to the centre and became the core, silica floated to the outside. This is important to life on earth – once we form the core the liquid outer core, (convection we have) , then we have a magnetic field, then we have a protection from meterorites, and now we have a atmosphere, and then since we don't have solar winds, we have oceans, setting the grounds for life on earth. Fossils – all of the things that have existed on earth, no longer exist now… Common way – a creature dies, and is buried and is preserved. Body cavities are filled in with something like silica, calcium carbonate, calcite, or iron, and this process is called mineralization – cause you are replacing what wa a cavity with a mineral. When you see a fossil in neat colours, it has nothing to do with the organism, it has to do with the mineral filled in that cavity. If its red, its cavity. “petrified wood” – rocks – bits of wood. Process of Mineralization - Creature dies, and soft parts are consumed by bacteria – decomposed, think about making yourself a face mask – if your going to use a face mask clay, you will get a nice mask for your face (detailed) , if you use sand it wont be very detailed. Same with fossils, you need fine grain sediments to get details – like CLAY. More sediments pile on top, eventually enough sediments pile on top that it lithifies, and turns into sedimentary rock. Mineral rich waters – water that has dissolved calcium carbonate or silica in it, will perculate through, and those minerals will precipate out of the cavities – it will fill the cavities of that creature making the beautiful mineral specimens we find inside the shells or fossils we are looking for Buried under all this rock – rocks are lifted up – erosion – otherwise they would be buried deep down. Erosion brough them up. Fossil – direct record of an organism actually being lived. Trace fossil – not fossilizing part of body – but trace, or footprint you left behind. Difference between trace fossil and body fossils. When creatures burrowed themselves into a place – that is a trace fossil. Some people t=edicate their life to finding trace fossils. Sedimentologists – love hate relationship with trace fossils – it can be useful seomtimes, but they disturb the sediments. – information from sediment – how thick the layers are = creatures creeping in, disturb the sediments and the records that they need. Fossils are important – to sedimentologists – to people in general studying life in the past – lots of clues about depositional environments – we want to know if a rock was deposited in a beach, desert, or lake. Fossils can piece together what a depositional environment was like. Assemblages – groups of fossils tend to be found together. If you went scuba diving, what kind of things will you find in the coral reef – you wouldn't expect to find penguins there… so certain things belong together – gives us clues about the environment… Fossil morpohology – coral – lots of different kinds of coral – brain coral – Human brain – fin coral, spread out, compact, all different morpoholgies or body types of coral shapes – the reason they do that is cause of their environment – things like light – the more light, they have different morphologies than those who have less light. The ones that live on the wave side on the ocean, need different body morphologies, than the ones that live in the areas wher the waves don't hit at all.. otherwise they get smashed up..morphology can give you a clue as to where you are. William Smith – Canal Engineer in England – digging canals all over England, and figured out that no matter where he went, he found the same order of fossils – that certain ones on the bottom he never found them at the top, it was always in the same order – faunel succession – use fossils to see which layers are older – no radiometric age dating – relative ages of layers based on fossils – stratigraphic principles. Geologic range vs. Geographic range – geologic range = time; how long did a creature live in time, did that specie exist in that time, or short lived, or still lives now? Goegraphic range = space; was it widespread in the world, did you find it in lots of places in the world, or restricted to a small area. Index fossil = to tel you how old a rock unit is, is one that has a short geologic range- but a wide geographic range – existed in many places in the world = that makes a great index fossil. Fossil hunters – trilobite growth- like snakes they shed skin, like snakes today, so you see lots of their skin in these fossil records. You can find really neat ones. Map to where we are going to today 1. Archean – following the Haedean – part of the Precambrian times. People still argue till this day, are they organic or inorganic – and you are trying to ascribe life to it? When life actually started to evolve = so there is a question beside 3.8 billion years (for life) 2. Before that, Haedean Era – meteo
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