EESA06 FINAL EXAM solutions to short answer possible questions.

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Environmental Science
Lisa Tutty

EESA06 Intro to planet Earth short answer possible questions: Your exam has three short answer questions (5 marks each) and one long answer question (10 marks) Homework - you CAN choose to answer a short answer question about ONE of your homework options. It is avoidable. Sample Questions: Lecture 7: Geologic Time, fossils and evolution - Compare and contrast the 2 main theories of dinosaur extinction 1. A well- known hypothesis for the K-T extinction involves a huge comet or asteroid striking Earth, sending massive amounts of dust and gas into the atmosphere and blocking sunlight. Earth’s surface would have been cold for decades. Many geologists conclude that the impact site, 65 million years ago, was the Chicxulub crater on the Yucatan Peninsula in Mexico. 2. Another possible cause of the extinction was massive outpourings of basalt in the Deccan traps in India. Huge eruptions could have put enough sulfur dioxide gas into the atmosphere to cause a winter that lasted decades. - Anoxia due to global warming - Especially severe for large animals - Small number if species survived - Adaptive radiation during the recovery phase - After extinction more species evolved - Discuss the contributions or 3 players to the level of the western theory of geographic time 1. Heavily based in Christian religion : - Earth was created in 7 days - Climate is fixed - Till, sand and gravel= Dilivium( biblical floods) - Strict biblical interpretation of earth’s history: rocks and landscapes result from Noah’s flood , more than one flood recognized , new life created each time so each layer contains different life forms. - Archbishop Ussher of Ireland gave an age of the Earth of about 5600 years, based on the study of the Old Testament. 2. Catastrophism: - Georges Cuvier - Idea that the Earth has been affected in the past by sudden, short- lived, violent events, possibly worldwide. - Paradigm shift? 3. *James Hutton 1726-97* - Recognized ‘unconformities’ within layers of rocks and the igneous origin of granite. - Unconformity: gap in the geologic record, rocks were missing due to erosion - Proposed concept of ‘ uniformitarianism’ : The present is the key to the past - Small constant changes - Earth must be older than 5,600 years (against the church) - Came into conflict with Abram Werner and ‘diluvanism’ and ‘catastrophism’ - 1788 “ no vestige of a beginning, no prospect of an end”. Constant cycle of deposition, burial, uplift, erosion and re-deposition. Same processes we observe today operated in the past. - ‘ Catastophism and creationism’ and ‘ uniformitarianism and evolution’ - Compare and contrast, relative and absolute age dating 1. Relative age dating: The first strategy is to determine the age of one rock relative to another, using a series of commonsense approaches collectively. 5 principles of relative dating- 1. Most sediments are deposited in horizontal layers 2. A younger sedimentary or volcanic unit is deposited on top of older units 3. A younger sediment or rock can contain pieces of an older rock 4. A younger rock or feature can cut across any older rock or feature 5. Younger rocks and features can cause changes along their contacts with older rocks 2. Absolute age dating: This is done by using numerical dating methods, most of which involve chemically analyzing a rock for the products of natural radioactive decay. Determining the ages of rocks using analytical measurements is called numeric dating. - What isotopic systems do we use to determine the ages of rocks and events? A number of elements have radioactively unstable isotopes, and geologists use these different isotopic systems to measure different types of ages on rocks, minerals, sediment, and other materials. Which isotopic system is used depends on what datable materials are present, the likely age of the materials, and the geologic history of the unit, Sedimentary rocks are the most difficult to date because most are composed of pieces of older rocks. Contrast: both methods use rocks to figure out the age of the earth, or historical events that happened in an area. Lecture 8: Economic Geology: Rocky resources and mining in Canada - Please create a chart comparing and contrasting the various types of ore deposits Magmatic arc For-arc basin Oceanic crust Oceanic Ridge Gold Lead Mg, Nickel Copper Veins, Porphyry Stratabound, Magmatic, Massive sulfides Copper, evaporites Evaporites Pegmatites Hydrothermal ore deposits: veins formed when volcanically heated water force their way up into a fracture. - Minerals precipitate out from hot water solutions. Magmatic ore deposits: chromite sinks to the bottom of a basaltic magma and accumulates in an almost pure layer. ( already separated by nature, unlike waste rock) - Formed as magmas differentiate Sedimentary ore deposits: evapourite deposits form when lake water or seawater evaporates and leaves its dissolved mineral behind. Eg) halite, gypsum - Placer ore deposits: Always contain minerals that originated elsewhere and were transported from their original source by water. - Mainly during floods - Residual ore deposits: Minerals left behind by the chemical weathering of a host rock Eg) aluminum from the tropics - Please create a chart comparing and contrasting the types of resources that are found in Precambrian ( layer 1), Paleozoic ( layer 2) and Pleistocene (layer3) deposits in Canada Precambrian Paleozoic Pleistocene ( layer 1) (layer 2) ( layer 3) Shield: big producers Sedimentary rocks: Quaternary are- 1. Oil, gas coal sediments: 1. VMS deposits: 2. Salt( evapourite 1. Placer minerals volcanogenic minerals) 2. Ore depostis: massive - Hydrothermal sulphides - Magmatic 2. BIFs - Sedimentary 3. Nickle - Placer - Residual - Tell me about your favourite Canadian economic mineral. Which layer hosts it? What type of deposits is it found in? What is it used for? Mineral: Gold Layer: layer I - the oldest layer ( Canadian Shield) Deposits: Gold forms primary deposits known as the lode deposits that are formed in solid rock which has concentration of gold and secondary deposits known as the placer deposits that are formed when the gold is transported by water from its original source. Gold also form residual ore deposits that are formed when the gold is left behind due to the chemical weathering of the host rock. ( in Island arcs) Uses: Gold has several uses, its primary use for the making of jewelry. I
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