GEY 100 Roadcut Cross-Section Assignments Composite Roadcut Cross-Secti Consi ge
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GEY 100 Roadcut Cross-Section Assignments Composite Roadcut Cross-Secti Consi geologic history and imagine a composite roadcut that takes igneous rocks, sedimentary ider all that you have leamed about rock types, structures and New England faul ts s them into a single cross-section, weaving together a New England style geologic history USING THE PROPER FORMAT FOUND 1. Show a composite roadcut with igneous, sedimentary, metamorphic rocks deformed by folds and faults This drawing will take a bit more planning as you are free to apply your geologic knowledge and creativity in combining the rock ty pes and structures in any way you want in order to make a single cross section. Pay special attention to the contact relations between the different features and rock units so that they are geologically accurate and realistic. These contact relations include: -igneous intrusive contacts that cut across and truncate all other contacts -sedimentary contacts as layers and layers of sediment accumulate with conformable relations where each layer is parallel to the next as well as unconformable relations as in the angular unconformity where younger layers truncate tilted lower layers -metamorphic layers are typically the oldest and cut by younger intrusions and covered by younger sediments. You can't have metamorphic and sedimentary rocks together in the same sequence without having an unconformity or a fault between the older metamorphics and the younger, unmetamorphosed sediment layers. 2. You might try this with a larger size paper (11"x 17" ledger size paper would work well) to give you more room to work out the geologic details. Landscape format in 8" x 11" works OK as well. Either way make your roadcut "canvas" as long as possible. 3. Keep it simple. Combine just one element from each of the previous units into your composite cross-section. Include elemen ts from the Igneous, Sedimentary, Metamorphic, Fold, and Fault roadcut cross section assi gnments. 4. Remember to use appropriate colors and patterns for the rock types portrayed and to include all rock types and features in your legend. Make the color spectrum work for you in designing your color scheme. 5. Try to keep your legend as a single stack to show a continuous geologic development. A larger and longer paper size will give you more room to develop a single stack legend 6. Use geologic time period age assignments for rock units and structures within your section in accordance with the geologic history of Maine and the general New England area. Triassic is for normal faults and basalt dikes; Late Devonian is for granites; Folds Thrust faults are Early Devonian in age; Sedimentary rocks would be Middle to Late Devonian as ancient mountain sediments locally preserved or Triassic arkoses along normal fault bounded rift basins; and metamorphic rocks could be older possibly Precambrian age "basement" rocks of the ancient continental crust.Explanation / Answer
Geology and the Formation of New England
The history of earth is about 4.5 B years past.There has been several changes to the present condition and the position of plate tectonics since those ages.Earlier our planet was like a huge ball of molten lava but it went on several cooling phases and then a thin outer shell was created.
The outer layer is what consists of continent size land masses which was earlier a super continent but gradually it broke into pieces and got seperated through the activities of plate tectonics.The size of crust is about eighteen miles thick and it floats on top of a semi molten rock called as mantle.
Its a very long passage of time when these process happened to what we ,in present , witness . Ex - At first around 4.5 BYA there was no rocks at all but after the cooling process started it gradually formed Pangaea , then very later came the era like Paleozoic or Mesozoic or the Cenozoic era so its a very long time span.
New England has a very diverse history in a very small geographic area like oceans , mountains , dinosaurs , rivers , earthquakes , lava flows etc..
Rock Types and Formation in New England Region.
Basic types of rocks are -
Igneous rocks are formed by cooling of magma .They can be intrusive as well as extrusive.If they are exposed on surface it is extrusive and then it undergoes several weathering.
Sedimentary is a result of weathering of igneous rocks under pressure in which they crack up into sediments like pebbles , shells etc and it usually contains fossils.
Metamorphic Rocks are formed in extreme heat and pressure under the earth surface and are usually shiny and has ribbon like layers.
Diastrophic Processes
Folds and Faults occur on earth's crust deep within which causes the surface to bend over.
It has several sub types depending on the type of folds or faults. Folds are caused in a very slow rate while faults are very rapid. In folding the crust is pushed upward through sides but it faulting the crust fracture or breaks down due to compression .These process forms several types of bents in the rock structure.
Younger rocks gets eroded while the older rocks stay subdued . There are several cases of superposition in which older rocks are lower and be identified while as a result of thrust the younger rocks gets exposed.
Figure can be drwan on A3 sheets for good understanding and the process is already explained on the way to pursue the structure drawig
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