Week 6 notes
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This 5 page Class Notes was uploaded by Jessica_Kline on Friday October 2, 2015. The Class Notes belongs to GEOL 101-01 at Ball State University taught by Kirsten N. Nicholson in Fall 2015. Since its upload, it has received 18 views. For similar materials see Planet Earth's geological environment in Science at Ball State University.
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Date Created: 10/02/15
GEOL 101 Week 6 0928 0930 amp 1002 Still Sedimentary Rocks 2 Marine formed at continental shelves and reefs there is much sediment there 3 Transitional these environments are fragile a storm could easily destroy a transitional environment lagoons estuaries deltas and beaches d There are two different types of sedimentary rocks detrital clastic and chemical 1 Detrital rocks are made from clasts which are lled in with sand and other small bits of rock and held together with cement they are classi ed by grain size claystone and shale are smallest then sandstone and quartz then gravel is the largest and whether they are a conglomerate rounded edges or breccia jagged edges Orthoclase is a potassium feldspar 2 Chemical sedimentary rocks are formed by chemical processes usually that chemical is water they are classi ed by their mineral composition carbonates are made of CaCO3 evaporites are made of NaCl siliceous are made of SiOz II Sedimentary rocks are nearly always found in layers a The Law of Original Horizontality states that all sediments were originally deposited in horizontal layers b The Law of Superposition states that older sedimentary layers are below younger sedimentary layers c Other features of sedimentary rock layers include bedding planes facies change cross bedding graded bedding and soft sediment deformation 1 Bedding planes layers that denote the top and bottom of of different sedimentary layers 2 Facies change lateral change in sedimentary rock layers 3 Cross bedding when water or wind pushes a grain of sediment up a hill and it rolls down the other side beaches and desserts 4 Graded bedding change in grain size in the same layer of rock 5 Soft sediment deformation sediments that are waterlogged are able to ow and deform d There are three main unconformities in sedimentary rocks angular nonconformities and disconformities 1 Angular unconformity when rock layers that have been tilted from plate movements and more layers are added on top usually in mountains 2 Nonconformity when erosion wear away rock for a period of time before more sediment is deposited 3 Disconformity different types of rocks are in the different rock layers Metamorphic Rocks I Metamorphic rocks are any rock that has been elected by heat pressure or a chemical substance usually water the original rock that forms into a metamorphic rock is called a protolith a There are ve different ways that metamorphic rocks can change other rocks recrystallization phase change metamorphic reaction pressure solution and plastic deformation 1 Recrystallization the mineral that the rock s made of stays the same but the grain size and shape change 2 Phase change the mineral changes but keeps the same composition such as diamonds can transform to granite under high enough temperatures but they are both still made of carbon 3 Metamorphic reaction new mineral crystals form from old minerals through chemical reactions 4 Pressure solution a rock is squeezed causing the grains to dissolve and form ions that can move and precipitate in a different place 5 Plastic deformation at super high temperatures rocks become plastic and can be elongated or attened b The three main reasons why geologists study metamorphic rocks is because they can be geothermometers measure temperature geobarometers measure pressure and for because they are worth money c There are four types of metamorphism dynamic contact regional and diagenesis 1 Dynamic syntectonic metamorphism is a result of high pressure and low temperatures usually at a subduction zone where an oceanic plate is sinking beneath a continental plate 2 Contact metamorphism is a result of high temperature and low pressure 3 Regional metamorphism is a result of high temperature and pressure usually at a mountain range where two continental plates are colliding 4 Diagenesis is not always considered a metamorphic process the temperature has to be over 500 degrees C and between 25 and 20 km deep this is how limestone is made d The metamorphic grade is the degree of temperature and pressure exerted on rocks 1 As the temperature andor pressure increases the grade increases 2 IndeX materials can only occur at certain temperatures and pressures e The two metamorphic textures are foliated textured and nonfoliated nonfoliated l Foliated rocks are formed by pressure that lines up the different minerals according to their shapes 2 Nonfoliated rocks do not have as much pressure applied to them quartzite marble granulites and argillites and greenstone which are soft f Other things 1 Porphyroblasts metacrysts are big crystals surrounded by a ne grain matrix 2 Deformational textures are friction breccia and chevron folds
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