Q&A Hero

Earth Science

Q: In the process of a magma cooling and crystallizing, if the original melt contained large amounts of iron, why isn't quartz a ferromagnesian mineral?
Q: The two branches of Bowen's reaction series are the continuous series and the discontinuous series. In what ways do the minerals in the discontinuous series differ from each other? And the minerals in the continuous series?
Q: Scenario: In the pursuit of scientific knowledge, you decide to bore a hole into the crust to see how the temperature changes. You start your borehole in Davenport, Iowa, where the geothermal gradient is 20C/km. Refer to the scenario above. How would you expect the geothermal gradient to change if this borehole were drilled near Yellowstone National Park? Why?
Q: Scenario: In the pursuit of scientific knowledge, you decide to bore a hole into the crust to see how the temperature changes. You start your borehole in Davenport, Iowa, where the geothermal gradient is 20C/km. Refer to the scenario above. How does this gradient compare to the average geothermal gradient?
Q: Scenario: In the pursuit of scientific knowledge, you decide to bore a hole into the crust to see how the temperature changes. You start your borehole in Davenport, Iowa, where the geothermal gradient is 20C/km. Refer to the scenario above. Assuming a temperature of 20C at the ground surface, what is the temperature at a depth of 2 miles?
Q: When teaching about igneous rocks, one trick instructors often implement to help students determine the igneous composition of the samples is to use the color of the rocks as a guide. Explain how the color of an igneous rock can often be used as an indicator of its igneous composition. Be sure to reference specific minerals for each composition.
Q: Magmas in the magma chamber of a volcano are often compared to soda to explain how the magma is erupted. How is magma like a bottle of soda? What happens to both substances when the pressure changes?
Q: What is the role that depth can play on cooling and crystallization of igneous rocks?
Q: Match the intrusive igneous rock with its extrusive equivalent. 1. Granite 2. Diorite 3. Gabbro A) Basalt B) Andesite C) Rhyolite
Q: Match the rock with the correct igneous composition. (Some choices will be used more than once.) 1. Rhyolite 2.Pumice 3.Gabbro 4. Diorite 5. Andesite 6. Obsidian A) Felsic B) Intermediate C) Mafic
Q: Match the igneous composition to its silica content. 1. Mafic 2. Felsic 3. Intermediate A) ~60% B) ~50% C) ~70%
Q: Most sills are intrusive igneous structures that display a fine-grained texture.
Q: Concordant plutons cut across existing structures while discordant plutons are parallel to existing features.
Q: Dikes tend to form as solitary structures.
Q: Temperatures will decrease with increasing depth into the Earth.
Q: Igneous rocks with an andesitic composition are found along volcanic island arcs.
Q: Mineral crystals that form early in the crystallization process will have better-developed crystal faces than later crystals.
Q: Plutonic bodies that have a surface exposure less than 100 km2are called ________. A) dikes B) stocks C) swarms D) batholiths
Q: Which of the following regions will primarily erupt silica-rich lavas? A) Oceanic mantle plumes B) Oceanic rift zones C) Continental margins D) Impact craters
Q: Peridotite that undergoes partial melting will create a melt enriched in ________. A) iron, magnesium, feldspars, and silica B) silica C) iron and magnesium D) feldspars and silica
Q: What is the definition of magma mixing? A) When magma mixes with fluids to become more dilute B) When rising magma melts surrounding country rock and incorporates it C) When one rising magma will overtake a second and the two intermix D) When magma incorporates more dissolved gases
Q: ________ will occur when continental collisions occur, thickening the crust and forcing some rocks to a depth where melting can take place. A) Decompression melting B) Rifting C) Extension D) Partial melting
Q: Welded tuff consists of ash surrounding large, jagged, irregularly-shaped pieces of material. What is this material and where does it come from? A) Mineral crystals that formed during cooling B) Rock fragments that erupted from the volcano C) Gas pockets from volatiles in the lava D) Slivers of volcanic glass from the lava
Q: ________ has a large percentage of voids and is lightweight, so therefore has the ability to float in water. A) Basalt B) Pegmatite C) Pumice D) Scoria
Q: Which of the following best describes a pegmatitic texture? A) Large crystals that form in a fluid-rich environment late in crystallization B) Porous texture resulting from escaping volatiles C) Fine-grained texture composed of microscopic crystals D) Several large crystals surrounded by a fine-grained matrix
Q: A ________ texture includes coarse phenocrysts surrounded by a phaneritic groundmass. A) pegmatitic B) porphyritic C) glassy D) aphanitic
Q: Where do ultramafic rocks form? A) At convergent boundaries B) In volcanoes C) At the Earth's surface D) At the upper mantle
Q: The granitic igneous rocks that make up the Sierra Nevada Mountains in California and Nevada are ________. A) extrusive B) intrusive C) metamorphic
Q: Will density increase or decrease with the crystallization of a magma? A) Decrease B) Increase
Q: When magma forms, it rises up through the crust. Why does magma rise? A) It is forced upward by pressure from the Earth's interior. B) It is less dense. C) It is uplifted by tectonism. D) It is forced out by volcanism.
Q: A ________ is a mushroom-shaped pluton that forms by injecting magma between sedimentary strata, forcing the upper layers to arch upward. A) dike B) sill C) batholith D) laccolith
Q: A ________ is a tabular, concordant pluton that is nearly horizontal and forms when magma exploits a weakness between sedimentary layers. A) dike B) sill C) batholith D) laccolith
Q: What is the name of the preexisting rock through which intrusive igneous bodies intrude? A) Acid rock B) Parent rock C) Stock D) Country rock
Q: Which process is thought to generate most felsic magmas? A) Decompression melting in a continental rift zone B) Crystal settling during magmatic differentiation C) Heat from basaltic magma partially melting overlying crust D) Friction along the crust in a convergent plate boundary
Q: Which of the following statements best describes the formation of secondary magmas? A) Decompression melting creates a mafic magma from mantle material. B) Iron-rich minerals will form in a cooling magma and leave the remaining melt with a more silicic composition. C) Partial melting of felsic rocks creates a silica-rich magma. D) Water dehydrating from a subducted plate will melt mantle material.
Q: If an igneous rock is heated, which mineral melts first according to Bowen's reaction series? A) Quartz B) Pyroxene C) Potassium feldspar D) Olivine
Q: If an igneous rock is heated, which mineral will be the very last mineral left to melt according to the Bowen's reaction series? A) Quartz B) Pyroxene C) Potassium feldspar D) Olivine
Q: What magma forms from the partial melting of mantle material? A) Ultramafic magma B) Magmatic differentiation C) Silicic magma D) Secondary magma
Q: The partial melting of mafic rocks would produce what composition of magma? A) Ultramafic B) Mafic C) Intermediate D) Felsic
Q: ________ describes the formation of one or more secondary magmas from a single parent magma. A) Magmatic differentiation B) Hydrothermal alteration C) Decompression melting D) Partial melting
Q: ________ describes how an entire suite of silicate minerals can form from a single basaltic magma as it cools and crystallizes. A) The theory of plate tectonics B) Moh's hardness scale C) Bowen's reaction series D) The geologic rock cycle
Q: What role does water play in generating magma? A) Water lubricates the path for subducting plates, allowing them to subduct deeper. B) Water lowers the density of the rock, allowing it to melt. C) Water cools the rock, preventing melting. D) Water lowers the melting temperature of the rock, allowing it to melt.
Q: What is the term used to describe increased temperature with depth in the Earth? A) Decompression melting B) Convection cells C) Geothermal gradient D) Hydrothermal alteration
Q: Which of the following statements best describes the relationship between pressure and melting point in the Earth's Interior? A) Higher pressure leads to lower melting points. B) Melting points of rocks are not dependent on changes in pressure. C) Higher melting points are determined by higher pressures.
Q: ________ is a felsic igneous rock with a meringuelike vesicular texture, consisting of very small holes, created by small shards of volcanic glass. A) Scoria B) Obsidian C) Granite D) Pumice
Q: What substance makes ion migration easier in the later stages of magma crystallization, which allows abnormally large mineral crystals to form and create pegmatites? A) Water B) Oxygen C) Silica D) Iron
Q: What creates the small holes found in a vesicular texture? A) Liquid water B) Volatiles C) Soluble minerals D) Weathering
Q: Which of these textures help geologists determine if a rock is of intrusive origin? A) Aphanitic B) Pyroclastic C) Porphyritic D) Phaneritic
Q: Which of these textures help geologists determine if a rock is volcanic in origin? A) Pegmatitic B) Aphanitic C) Porphyritic D) Phaneritic
Q: Which igneous texture has visible crystals that are a few millimeters across? A) Phaneritic B) Aphanitic C) Pegmatitic D) Porphyritic
Q: What is the geologic definition of texture? A) How the sample feels to the touch B) The mineral content of the sample C) The percentage of silica in a sample D) Size, shape, and arrangement of mineral grains in the sample
Q: Which two minerals define a felsic composition? A) Pyroxene and amphibole B) Muscovite and biotite micas C) Quartz and potassium feldspar D) Plagioclase feldspar and biotite mica
Q: Peridotite is the main constituent of which part of the Earth? A) Crust B) Magma chambers C) Rift zones D) Upper mantle
Q: Which of the following minerals is nota ferromagnesian mineral? A) Olivine B) Potassium feldspar C) Pyroxene D) Biotite mica
Q: Which mineral group makes up most igneous rocks? A) Carbonates B) Sulfides C) Silicates D) Halides
Q: What was the rate of cooling and the environment of formation for an extrusive igneous rock and why? A) Slow because the magma was insulated below the surface B) Fast because it was erupted from a volcano C) Slow because it cooled in a volcanic lava flow far from the vent D) Fast because it cooled 6 kilometers below the surface
Q: Select the choice below that best describes the role of volatiles in an ascending magma. A) Volatiles increase the rate of crystallization in intrusive structures. B) Volatiles will force the magma to contract as it rises. C) Volatiles will shatter surrounding rocks, making it easier for the magma to rise. D) Volatiles will expand with decreasing pressure, then melt upward.
Q: Which of the following substances is not a volatile found in magma? A) O2 B) CO2 C) H2O D) SO2
Q: What is a volatile? A) A hostile person B) Solid mineral crystals in a melt C) Gases dissolved in a magma D) The liquid portion of a magma
Q: What three components make up most magmas? A) Silicon, potassium feldspar, and muscovite B) Water, melted rock, and solid crystals C) Lava, ash, and gas D) Liquid portion, solid portion, gaseous portion
Q: ________ is molten rock that is below the Earth's surface and retains most of its volcanic gases. A) Lava B) Pumice C) Magma D) Volatiles
Q: Which mineral formation process would have been responsible for creating a mineral deposit such as this? A) Biological secretions of calcium carbonate B) Mineral precipitation from slowly moving groundwater C) Mineral precipitation from evaporating water D) Crystallization from molten material
Q: Using this image, label the atoms with the appropriate elements to make the silica tetrahedron. 1. A 2. B 3. C 4. D 5. E A) Oxygen B) Silicon
Q: What type of atomic bond is shown in the figure above? A) Hybrid B) Metallic C) Covalent D) Ionic
Q: Label the atomic properties of carbon as they would be found on the periodic table. 1. A 2. B 3. C A) Atomic mass B) Atomic symbol C) Atomic number
Q: Using the cleavage planes and shapes in this image, list one mineral example for each crystal.
Q: Using the samples in this image, indicate the number of cleavage directions this crystal displays. (Please note that cleavage surfaces do not equate to cleavage directions.)
Q: Using the samples in this image, indicate the number of cleavage directions this crystal displays. (Please note that cleavage surfaces do not equate to cleavage directions.)
Q: Assuming well-formed crystals, how many cleavage surfaces are present on the sample in this image? (Note: Cleavage surfaces are not cleavage planes.)
Q: Assuming well-formed crystals, how many cleavage surfaces are present on the sample in this image? (Note: Cleavage surfaces are not cleavage planes.)
Q: Write a simple chemical formula showing how the component elements of the silicate ion affect its net charge.
Q: Certain diamond companies use the advertising slogan "Diamonds are forever." Why, from a geologic perspective, might this not be accurate?
Q: Describe how magnesium can be exchanged for iron in olivine without destroying the internal framework of the mineral.
Q: Two unknown minerals are placed before you for identification. You decide to test each mineral's hardness. Mineral A will scratch a piece of glass. Mineral B will not. Which mineral is harder? How do they compare to the specific hardness of the glass?
Q: Students new to mineral identification often confuse shiny, dark-colored nonmetallic minerals for those minerals with a metallic luster. Explain how streak can be useful for telling these minerals apart.
Q: Restricted ocean basins located in warm climates will experience high rates of evaporation, which will result in the creation of evaporate minerals such as gypsum or halite. When such a solution containing dissolved mineral matter evaporates, why does the mineral matter precipitate instead of evaporating with the water?
Q: Why do atoms exchange or share electrons?
Q: Which of the following substances is not a mineral: gold, water, ice? Why?
Q: If concrete is made by mixing cement with gravels and sands, is concrete a rock? Why or why not?
Q: Consider the definition of a mineral. Why would a synthetic gemstone fail this definition and not be considered a true mineral?
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