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Lecture

# GGR201.docx

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Department
Geography
Course
GGR201H1
Professor
Joe Desloges
Semester
Winter

Description
GGR201 – Geomorphology th January 14 , 2014 “Table top” is used for flat surfaces. Mesa – flat, low-topped sedimentary rocks. Seamount – flat top that was a volcanic feature that was exposed to above-sea level, but then is eroded and develops corals around it, and is now below the surface. On midterm and final, there will be descriptions of pictures (sometimes with, sometimes without interpretation). Landforms are functions of process, structure and time. This can be reinterpreted to show that landforms are the result of forces working on the earth surface (driving forces of energy), materials of the landscape (which form a suite of resisting forces), and what stage in time. In order to perform work (geomorphic work) to sustain the processes (which drive the system), you need: primary forces at play (the sun, gravity, internal/tectonic). Watt = work energy = joules/time = kgm^2/s^3 The amount of incoming solar energy = the amount of outgoing solar energy from the Earth. Internal/tectonic energy has a disproportionate amount of influence on geomorphic processes, so even though the sun is about 250 times stronger, the sun doesn’t do much in that sense. Polar fronts = vortex How is energy transferred? a) Processes of advection of air masses (movement of air currents, driven by differential pressure gradients). b) Advection of water in ocean circulation (salinity, density affect ocean currents) c) Latent heat transfer Hydrological balance: R = P +/- S. R = river, P = precipitation, S = storage When you have a mid-oceanic rift, there is subduction underneath the continental crust, as well as compression at the top of the continental crust. Diagram of different rocks as well as how rocks are transported may be on midterm/final. On that diagram, 1. Hydrological cycle, 2. Rock cycle, 3. Ocean currents There’s a coupling between what the ocean currents and the atmosphere do. Energy transfers lead to producing a “stress” on the Earth surface (materials). Tau = Shear stress = pressure kgm/s^2, or pascals. Kilopascals = millibars. Week 2 Readings Chapter 2 – The Driving and Resisting Forces Geomorphological processes – natural mechanisms of weather, erosion, transportation and deposition that result from the application of physical or chemical forces to materials and landforms. Geomorphological events of moderate size account for the greatest proportion of work, due to the frequency of them occurring. Week 3 Lecture Moraines are evenly spaced ridges left behind by glaciers. Recessional moraines are from when a glacier is retreating and stalls for periods of time and leaves something behind. There are ~120 active volcanoes on our planet at the moment. Epirogenesis – folding of mountains that is very gentle which results in tilted layers of the mountain If a mountain is under extreme pressure, then the layers of it will be folded and curved (i.e wavelength). Margins of plates are dominated by volcanism and orogensis Plate interiors are dominated by epirogenesis Mount Logan is the highest mountain in Canada Shape, position, etc, will help you understand the scale of landforms and help you learn how to classify them. Weathering After weathering, you are left with: 1. Rocky minerals that resist destruction (end product). 2. New minerals that are created by the weather process. 3. Potential of organic debris being added to the weathered zone (i.e soil). Only really need to worry about 3 groups of minerals, as these groups control how the earth will be weathered: 1. Quartz (SiO2), accounts for 12% of crust. K-feldspar and playoclasic-feldspar (kAlSi3O8 and CaMaAlSi3O8, respectively), about 12% and 39% of crust 2. Micas, olivine, magnetite, pyroxene, made up of k(MgFe)(AlSiO3), about 25% of crust. 3. Clay- H4Al2SiO9, about 5%. Calcite and dolomite, made up of CaMg(CO3)2, about 2% of crust. Two igneous (or volcanic) rock groups dominate: 1) Felsic – granite and syanite 2) Mafic – basalts/galbro, rich in magnesium and iron Iron- and magnesium-rich minerals break down very easily and are on the LHS of the goldich dissolution series. Lowest temperature minerals form quarts, high temperature is at the top of the goldich dissolution diagram. Quartz has covalent bonds. Olivine have ionic bonds (one atom gets two electrons, other atom gets none, so one has negative charge, other has positive). How acidic the water is ultimately determines the ability of it to break up rock particles. Degree of saturation affects how easily a solution will accept more ions. Aluminum is the least mobile element. Porosity: how much water rocks can hold Permeability: how fast water moves throughout the rock system High porosity makes weathering rates decrease because it’s harder to get the water to move throughout the system. Dissolution: dissolving of water, NaCl will dissolve it by attaching onto the existing ions. Hydrolysis: Orthoclase produces quartz and kaolinite (clay mineral – HySiO2) when it is exposed to water. Hydration: Hematite  add water to it and it absorbs water. you can also heat it up and drive away the water. Oxidation: oxidizing something is adding oxygen to it, but you can also take away oxygen (which is called redox). Olivine is the least stable. Iron is oxidized (loses electron) to hematite. Carbonation: rainfall is naturally acidic. Since there is carbonic acid in our atmosphere, rainfall can have a pH of 4-5. Carbonation will result in karst landscapes where there is a lot of limestone. Requirements for Karst processes: 1. Considerable thickness of limestone, which has to have low primary permeability (actual component of solid rock-mass of it cannot transport water very well. But, it has to have a high secondary permeability (in the various cracks of the stone, water must move very thickly). This forces the water to lie in a certain area (the bedrock?). 2. Considerable uplift above sea level. 3. High annual precipitation. Karst landforms: Just a bit of magnesium in limestone will cause them to be much more resistant to chemical weathering. The four images of karst landforms go from an extremely small scale to an extremely large scale. If the drainage of a landscape tends to go inward to the landscape (i.e sinkholes), it is indicative that the landscape is underlied by limestone which has been chemically weathered. In Poland, this is called Poljes, in Europe it is called dolmine. Stalactites are on top (you have to hold on tight). Karst caverns and caves have stalagmites and stalactites in them. The stones in them are called “flowstones” because they just flow into them. Speleometh: groups of flowstone. The acidity of the sweat on your hand will discolour stalagmites/stalactites. Theories: Figure a) If you are chemically saturated, then you cannot exchange ions with anything else. Figure b) Epipheratic (at the water table) components of this is where all the caverns and caves will form. Figure c) everything happens below the water table. The water is chemically saturated, but If there is enough pressure, you can push water through the spring, which will produce cave/cavern activity. When you break a rock, its joints end up being at 90 degrees to it because those are the most susceptible to breakage. Frostquake: lots of stress on a system by freezing/thawing. Pressure release will be on exam? In Canada, we’ve had a legacy of glacial ice which has had a lot of pressure on the underlying rocks. It has been expanding at about 25cm/100 years. Rocks are extremely poor thermal conductors. The heat does not penetrate at all, just remains at the surface. Onion skin weathering: daily/seasonal changes tend to slowly create weaknesses in the rock and exfoliate it, which produces layers. Exfoliation – no matter how much heat you put into it, it will not speed up the process unless you add a bit of water to it. This is because chemical and mechanical weathering are not separate processes, but rather will combine. Tor – single peak of rock. Slake – Shear shale off of rocks and make a pile of it. Blockfield – field of blocks; “felsemeer” – in situ chemically and mechanically weathered bedrock. In situ – non-moving. Any way that particles rub up on one another will cause some kind of mechanical weathering. Biological agents have two scales: microbial – small plants, and as big as tree roots. Tree roots grow into the cracks of dolomite and then expand and end up prying apart the cracks. 1000-1500 earthworms per cubic meter of soil in southern Ontario which break up soil and make it good. Long terms effect of weathering slide: diagram on it is good for exams/tests; ties in everything that we’ve been talking about. Can either give us axes and tell us to fill it in, or give us the diagram and ask us what influences what and how intens
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