GEOL1011_Major_AS2_Nov92020

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GEOL 1011: Introduction to Geoscience 1 Jordy Major T00532765 GEOL 1011 Assignment 2 Nov 9, 2020 Assignment 2 This assignment is worth 12% of your total course mark. Please type your answers directly into this document and submit the assignment to your Open Learning Faculty Member. This assignment includes two field exercises. You are expected to go out into an area close to where you live, take some photographs, and describe what you see. Part A: Short-Answer Questions ( 20 points in total ) Answer the following questions as succinctly as you can. None of the answers should be more than a couple of sentences (100 words or less). Please type your answers into the grey boxes. 1. Explain why the presence of carbon-dioxide in the atmosphere is important to weathering. ( 2 points ) The presence of carbon-dioxide in the atmosphere is important to weathering because it produces weak carbonic acid when combined with water which breaks down the rocks. 2. What are the main products of weathering of igneous rocks? ( 2 points ) Typical weathering products of igneous rocks are quartz as sand grains, clay minerals, serpentine, chlorite, calcium, and iron oxide minerals. 3. Describe some of the ways that soil can be degraded if we don’t take care to look after it. ( 2 points ) Forestry and agriculture can degrade soil because when vegetation is removed, the soil is no longer held in place and it is now exposed to water and wind. The water and win subject the soil to erosion. 4. How does the velocity of moving water affect the transportation of sedimentary particles? ( 2 points ) The speed at which the sedimentary particles move and the size of the particles is dependent on the velocity of water – the faster the water flows, the larger the particles it can move. 5. What is chert made of, and what is the typical source of that material? ( 1 point ) Chert is a chemical sedimentary rock that is made from ions that were TRU Open Learning

2 Assignment 2 transported in solution and converted into minerals. The source of chert is usually from deep-oceans sedimentary rocks. 6. Describe the tectonic origins of rift basins and forearc basins. ( 2 points ) A rift basin is formed where the continental crust is pulled apart and the crust on both sides of the rift subsides. A forearc basin is located between the subduction zone and the volcanic arc. It is formed by friction between the subducting plate and the overriding plate, which pulls down part of the overriding plate. 7. What is the typical origin and depositional environment of normal (i.e., fining upward) graded bedding? ( 2 points ) Many graded beds form in a submarine-fan environment. The sediment flows down from a shallow marine shelf onto the deeper sea floor. 8. With respect to sedimentary rocks, what are the criteria for defining a “formation”? ( 1 point ) A formation is distinct bed (from the beds above and below) that is thick enough to be shown on geological maps. 9. Explain why mineral stability is important to metamorphism. ( 2 points ) Mineral stability is important because when a rock is subjected to increased temperatures, some minerals could become unstable and start to recrystalize into new minerals. 10. Describe the nature of foliation in gneiss. ( 1 point ) The nature of foliation in gneiss is for the mineral to separate into bands of different colours. 11. Describe the rock “skarn” and the conditions under which it forms. ( 2 points ) Skarn is a type of metamorphism where a hot pluton intrudes into carbonate rock and the magmatic fluids flowing through change the chemistry resulting in the deposition of minerals that would not normally exist in the igneous rock. 12. Provide the names and age ranges for the Periods of the Cenozoic. ( 1 point ) The periods of the Cenozoic are the Paleogene (66-23mil years ago), the Neogene (23-2.6mil years ago), and the Quaternary (2.6mil years ago - present). Part B: Exercises ( 45 points in total ) B1: Observe and document weathering ( 15 points ) Weathering is happening all around us, although most of the time we don’t even notice it. For this exercise, you need to look around the region where you live, find some evidence of mechanical or chemical weathering, photograph it, and then TRU Open Learning

GEOL 1011: Introduction to Geoscience 3 describe what you see in the photo. Some examples are freeze-thaw weathering of a rock exposure, tree-roots pushing rocks apart, lichen growing on a rock, a rusty stain on a rock exposure, frost-heaving on a road, a crack in a building stone or sidewalk, dissolution or other weathering of a headstone or other old monument, and so on. Ask your Open Learning Faculty Member for help if you can’t think of a place to look. Include your photo with your response, and write a few sentences about the weathering effects that you can see in the photo. Provide some evidence in the photo that you were there when it was taken (e.g., a piece of paper with your name on it, or your hand with three fingers showing). The photo is an example of lichen growing on a rock. This is a type of chemical weathering. The lichen creates chemicals produced by colonies of algae and fungi that break down the rock. B2: Photograph and describe a depositional environment ( 15 points ) Sediments are also being deposited all around us, and for this exercise you need to go and find and photograph a depositional environment. Some examples might be a section of a stream, lake, wetland, beach, delta, bay of the ocean, and so on. Don’t hesitate to ask your Open Learning Faculty Member for help. Include a photo with your response. Describe what type of sediments (clay, silt, sand, pebbles etc.) you think are being deposited (based on what you can see or what you think should be there), and speculate about how long this particular sedimentary basin has existed. Do you think it’s likely that these sediments will be turned into rock at some time in the future, or is it more likely that they will be re-eroded and deposited elsewhere? Again, provide some evidence in the photo that you were there when it was taken. Examples of sedimentary basin photos are provided below. TRU Open Learning

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4 Assignment 2 © Steven Earle. Used with permission. This photo is an example of a sedimentary basin (Barnes Lake) in Barnhartvale, Kamloops. A small creek slowly flows in and out of the lake therefore only small sedimentary particles are being carried through. The basin consists of mostly silt with traces of organic matter and sand at the shore. It is unlikely that these sediments will be turned to rock because they are very young in geological time (Quaternary period) and they will be re-eroded and deposited elsewhere. B3: Understanding the Mt. Polley area geological map ( 15 points ) The following questions refer to the geological map of the Mt. Polley area in central British Columbia, and are based on information in the map legend, the map symbols, the cross sections, and on the map itself: 1. What is the approximate age range (in years) of the youngest deposits in the map area? ( 2 points ) The youngest deposits in the area are the Quaternary thick alluvium: Qal, which have the approximate age range of 2.6 Ma to present day (the Quaternary Period). 2. Provide the rock-type names (and unit codes) and ages of any three of the layered units that are entirely sedimentary in origin. ( 3 points ) E Ks: Mudstone siltstone, shale and fine clastic sedimentary rocks. 55.8 to 33.9 Ma. MJ Dcg: Polymictic conglomerate, sandstone, graded siltstone. 176 to 161 Ma. TRU Open Learning

GEOL 1011: Introduction to Geoscience 5 EJr Sn: Brown-grey siltstone, sandstone, and calcareous conglomerate. 199 to 182 Ma. 3. Based on the map and cross-section A-A’, how would you describe the relationship between the Unnamed Cretaceous Conglomerate and the rocks underneath it? (You may need to refer to the “Symbols” explanations on the map.) Why is this rock called “polymictic”? ( 3 points ) The relationship between the Unnamed Cretaceous Conglomerate and the rocks underneath is that they are nonconformed. The rock is polymictic because it is composed of several types of rocks with fragments of different compositions and stones of different sizes. 4. The oldest unit shown on the map is primarily made up of metamorphic rocks. What are the main rock types, and in what type of metamorphic environment did they form? Where on the map can you find this rock type? ( 3 points ) The main rock types of the oldest unit on the map are Gneiss, schist, marble, amphibolite, conglomerate, and quartzite. These formed in medium to high grade metamorphic environments. On the map, this rock is in slightly to the right of the N and in the NE corner. 5. The intrusive rock north of Gavin Lake has been isotopically dated. What dating technique was used? What is the numerical date, and to what geological period does this date correspond? ( 3 points ) The intrusive rock north of Gavin Lake (MJ qm) was dated using the K-Ar dating technique. Its numerical date is 168 Ma and the Geological period is Mesozoic. 6. The Gavin Lake area intrusion is depicted in Cross Section B. Describe its age relationship with the rock into which it has intruded. ( 1 point ) The age relationship between MJ qm and Lt Ns is that the latter is older, from the Late Triassic era and contact between them has been assumed. TRU Open Learning

6 Assignment 2 Part C: Longer Questions ( 35 points in total ) Please answer the following questions. Write as much as you think is necessary to answer each question, but don’t forget that someone has to read what you write, so be as concise and clear as possible. You do not need to reference the text or the material in the Course Units (except images and quotations), but if you use any outside sources, please provide in-text citations. Use any referencing style that you are comfortable with. 1. Describe some of the factors that control soil development, and explain why podsols are the most common soils in many parts of southern Canada. ( 10 points ) Soil is developed through accumulation and decay of organic matter and through chemical and mechanical weathering processes. Some of the important factors include climate, type of parent material, the slope of the surface, and amount of time available. The best climate for soil formation is temperate to tropical conditions, where chemical weathering and plant growth is faster. An example of the effect of parent material is that quartz-rich material develops sandy soils. The slope of a surface affects soil because it can only develop where surface material is frequently moved. Time is a large factor because soil takes thousands of years to develop. For example, podsols are the most common soils in many parts of southern Canada because the region was glaciated until 14 Ka therefore the soil is young and not well developed. 2. Explain what sedimentary rocks can tell us about past environments, focussing on the characteristics of sedimentary grains, the types of sedimentary structures present and the presence and types of fossils. ( 15 points ) Bedding Sedimentary rocks that are separated into layers can indicate seasonal differences, changes in locations of rivers, or tectonic changes. Fossils Fossils are found in groupings with other fossils and rocks. The type of fossils can determine a past environment. For example, a coral fossil suggests a tropical climate, a thin shell on a creature could suggest a calm environment, and the type of creature could determine if the area had salt or freshwater. Other things can be fossilised, such as wood, which would mean trees existed in the environment. Finding a large amount of fossils could indicate an abundance of resources and environmental diversity in the area. Sedimentary Grains The size of sedimentary grains can give us information of the transportation and deposition of sediment. For example, large grains could suggest that water with high velocity passed TRU Open Learning

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GEOL 1011: Introduction to Geoscience 7 through the area. Rounded cobbles and pebbles on a beach could point to strong waves and windy environment that weathered the grains. 3. Discuss the role of plate tectonic processes in regional metamorphism, and explain why isostasy is important to regional metamorphism. ( 10 points ) Regional metamorphism happens in the continental crust when rocks are buried deep in the crust. Plate tectonics play an important role because the process is often caused by convergent plate boundaries and the formation of mountain ranges. Isostasy is important to regional metamorphism because it theorises that the Earth’s crust is floating on the mantle. During mountain building, the extra weight causes the crustal rock to sink into the mantle, thus causing regional metamorphism. TRU Open Learning