MSCI 112 Final Exam Questions & Answers 2024/2025

MSCI 112 Final Exam Questions & Answers 2024/2025 An igneous rock was formed with 8000 radioactive (parent) atoms but contains only 1000 radioactive (parent) atoms today. If the half-life for the radioactive element is 10 million years, the rock is ___ million years old. - ANSWER-30 Which of the common components of siliciclastic sediment are likely to have been formed from the original sediment source rock through chemical weathering? - ANSWER-clays Which is the largest division of geologic time? - ANSWER-eons Which process causes subsidence in a sedimentary basin? - ANSWER-both deposition of sediments and regional downfaulting What is a nonconformity? - ANSWER-a gap in the geologic record bounded below by metamorphic or igneous rocks and bounded above by sedimentary rocks The study of the history of ancient life based on the fossil record is called: - ANSWER-Paleontology The remains of algae, bacteria, and other organic material may accumulate as organic matter on the seafloor that can be transformed into: - ANSWER-oil and gas Why does mechanical weathering of an exposed rock cause chemical weathering to take place more quickly? - ANSWER-broken rock fragments have more exposed surface area Which of the following is a clastic sedimentary environment? - ANSWER-alluvial Which is the most common type of chemical or biological sedimentary environment? - ANSWER-carbonate environment The half-life of a radioactive material depends on: - ANSWER-the half-life is constant for any one material The Precambrian represents about what fraction of the age of Earth? - ANSWER-90% What is the geologic time scale? - ANSWER-a division of Earth's history into time intervals beginning and ending at times when fossils changed significantly What is NOT an example of physical weathering? - ANSWER-dissolution of some minerals in a rock, causing it to weaken Why does most of our information on geologic history come from continental rock? - ANSWER-oceanic crust older than 200,000,000 years has been recycled by subduction What type of event might lead to the development of an unconformity? - ANSWER-sea level drops Cross-bedding forms on ___ of a sand dune - ANSWER-the downwind side How do most carbonate sediments and rocks in shallow environments form? - ANSWER-they are bioclastic materials Coal is formed from: - ANSWER-peat What process must occur before an intrusive igneous rock can be weathered? - ANSWER-uplift Which class of rock-forming minerals is the most common in Earth's crust? - ANSWER-silicates The lead-zinc province of the Upper Mississippi Valley in the mid-western United States is an example of a _________ deposit - ANSWER-disseminated hydrothermal The hardness of a mineral depends on the: - ANSWER-strength of chemical bonds Minerals form by which of the following processes? - ANSWER-both crystallization and precipitation Which of the following is a good estimate of the melting temperature of a typical crustal rock? - ANSWER-700°C How do plate tectonics and the climate system of Earth interact? - ANSWER-1. Mountain ranges divert air flow and alter precipitation patterns 2. Volcanic eruptions eject rock material into the atmosphere 3. Weathering and erosion transfer rock material to the ocean where they are subducted Which of the following is an example of an igneous rock? - ANSWER-granite What type of chemical bonding holds the Na and Cl atoms together in table salt (NaCl)? - ANSWER-ionic bonds Which of the following minerals is commonly found only in metamorphic rocks? - ANSWER-staurolite What Earth system is NOT involved in the rock cycle? - ANSWER-geodynamic system What is the difference between pyroxene and amphibole? - ANSWER-different chemical composition If a geologist wants to determine whether an igneous rock sample cooled within Earth or on its surface after an eruption, what property or feature would the geologist want to examine? - ANSWER-texture Metamorphism causes changes in which properties of an existing rock? - ANSWER-mineralogy, chemical composition, and texture Increases in temperature will normally cause rock density to ______, while increase in pressure cause density to _____________ - ANSWER-decrease; increase What is a vein deposit of an economically important mineral? - ANSWER-a sheetlike deposit of minerals precipitated from rapidly cooling hydrothermal solutions What is NOT an example of a silicate mineral structure? - ANSWER-triple chain Which minerals is an example of a carbonate? - ANSWER-calcite A mineral is usually inorganic; which of the following can be considered a mineral? - ANSWER-calcite formed from shells of oysters T/F: a mineral must always have exactly the same chemical composition - ANSWER-false An igneous intrusion whose boundaries lie parallel to the layering in the surrounding country rock is considered to be: - ANSWER-concordant A large igneous body formed at depth in Earth's crust is a: - ANSWER-pluton What evidence led Hutton to conclude that granite formed by solidification of magma deep inside Earth? - ANSWER-1. alteration of sedimentary rock by heat next to granite 2. volumes of granite fractured existing sedimentary rock 3. granite is composed of coarse, interlocking crystals Most magmas form at what types of plate boundaries? - ANSWER-subduction zones and mid-ocean ridges Which list would you expect to list correctly a set of rocks in order of increasing density? - ANSWER-granite, andesite, gabbro If a geologist examines a thick lava flow that solidified after flowing away from a volcanic vent, where would she expect to find the coarsest texture in the flow? - ANSWER-in the center of the flow At which type of plate boundary would you expect fluid-induced melting associated with added water content to be most important? - ANSWER-subduction zones What statement correctly describes an ophiolite? - ANSWER-it is a set of deep-sea sediments, basalt rock, and mafic intrusions found on land The process of magmatic differentiation explains how: - ANSWER-rocks of varying composition can arise from the same parent magma Fractional crystallization is the process by which: - ANSWER-crystals formed in a cooling magma are removed from the remaining magma Igneous rocks with crystals too small to be seen without a microscope are: - ANSWER-fine grained In the general theory of plate tectonics, at which particular settings do igneous rocks form? - ANSWER-convergent/divergent boundaries and hot spots The most plentiful minerals in peridotite are: - ANSWER-pyroxene and olivine Which process is most important for causing the formation of magma associated with mantle plumes (hot spots)? - ANSWER-decompression melting What does the viscosity of a liquid measure? - ANSWER-the resistance of a liquid to flow At which type of plate boundary would you expect fluid-induced melting associated with addition of water to rock to be most important? - ANSWER-subduction zone What is the effect of water on rock melting? - ANSWER-water decreases the melting temperature of a rock What happens to temperature with increasing depth in the Earth? - ANSWER-temperature increases faster with depth where Earth's crust is being stretched What features is NOT associated with a divergent plate boundary? - ANSWER-deep sea trenches At approximately which time period did scientists begin to note observations such as coastline shapes that could be explained if the Americas and Europe had been part of a larger continent? - ANSWER-about 1600 What evidence helped give strong support for the hypothesis of seafloor spreading at mid-ocean ridges? - ANSWER-1. samples of young basalt from Atlantic Ocean Sea floor 2. frequent earthquakes along ocean ridges 3. a rift present along the crest of ridges Continues...