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geology final
| Question | Answer |
|---|---|
| Describe the ways in which geology affects our everyday lives. | Geology provides resources such as minerals, metals, energy resources, groundwater, and building materials. It also helps us understand and predict natural hazards such as earthquakes, volcanoes, landslides, and floods. |
| How are the rock cycle and plate tectonics related? | Plate tectonics drives the rock cycle by creating, destroying, uplifting, burying, and melting rocks. Movement of tectonic plates causes the processes that transform rocks from one type to another. |
| Briefly explain how the themes of plate tectonics, organic evolution, and geologic time provide a cohesive story of the history of Earth. | Plate tectonics explains changes in Earth's surface, organic evolution explains changes in life through time, and geologic time organizes these events into a timeline. Together they provide a complete history of Earth and its development. |
| Briefly explain how geologists can formulate theories about events that occurred on Earth before humans were here to make observations. | Geologists study rocks, fossils, landforms, and geologic structures to interpret past events. They use scientific principles such as uniformitarianism to infer how ancient processes occurred. |
| Briefly explain the importance of the geologic time scale. Organizing earth's history into manageable intervals and allows comparison of events worldwide. | The geologic time scale organizes Earth's 4.6-billion-year history into manageable intervals. It allows geologists to compare rocks, fossils, and events from different parts of the world. |
| Briefly explain the importance of the principle of uniformitarianism to the study of historical geology. Present day processes help explain ancient geological events. | Uniformitarianism states that the same geologic processes operating today operated in the past. This principle allows geologists to use present-day observations to interpret ancient geologic events. |
| What were the major lines of evidence for continental drift as presented by Wegener in the early 20th century? | Wegener used the fit of continents, matching fossils across oceans, matching rock units and mountain ranges, and evidence of ancient climates such as glacial deposits. Together these suggested that continents were once joined. |
| Explain how mountain ranges can be used as evidence to support continental drift. | Mountain belts on different continents have similar ages, rock types, and structures. When the continents are fitted together, these mountain ranges form continuous belts. |
| How does fossil evidence support continental drift? | Identical fossils of plants and animals are found on continents now separated by oceans. Since these organisms could not cross vast oceans, the continents must once have been connected. |
| How is the phrase "the present is the key to the past" used in creating evidence for continental drift? | Geologists study modern geologic processes and environments to interpret evidence preserved in ancient rocks. This helps explain how continents could have been joined and later separated. |
| Explain why submarine hydrothermal vents are interesting to scientists. | Hydrothermal vents support unique ecosystems that do not depend on sunlight. They also provide information about seafloor spreading and the formation of new oceanic crust. |
| How does seafloor spreading explain the movement of the continents? | New oceanic crust forms at mid-ocean ridges and moves away from the ridge as more magma rises. This movement carries the tectonic plates and continents with it. |
| Briefly explain how magnetic reversals in oceanic crust and fossils in ocean sediments are used to construct a magnetic time scale. | As basalt cools at mid-ocean ridges, it records Earth's magnetic field. Matching magnetic reversal patterns and fossil ages allows geologists to date rocks and build a magnetic time scale. |
| Briefly describe what happens when divergent plate boundaries form within a continent. | The continental crust is stretched and thinned by tensional forces. Faults develop, a rift valley forms, and continued spreading may eventually create a new ocean basin. |
| How are hot spots used for determining the absolute motions of plates? | Hot spots are thought to remain relatively stationary while tectonic plates move over them. The ages and positions of volcanic chains formed above hot spots record the direction and rate of plate motion. |
| What is the definition of a mineral, and what do each of the parts of the definition mean? | Naturally occurring formed by earths processes (not man made) Inorganic not from a living thing Solid fixed shape/volume Definite chemical composition specific chemical formula (or limited range crystal structure atoms arranged in repeating patterns |
| How do a rock and a mineral differ? | A mineral is a naturally occurring substance with a specific chemical composition and crystal structure. A rock is an aggregate of one or more minerals that are physically combined together. |
| For each of the following subatomic particles, state where it can be found and what its charge is: proton, electron, and nucleus. | Protons are found in the nucleus and have a positive charge. Electrons move around the nucleus and have a negative charge, while neutrons are found in the nucleus and have no charge. |
| What are radionctive isotopes, and why are they important to geologists? Unstable atoms that decay over time into stable forms. | Radioactive isotopes are unstable atoms that naturally decay into other elements over time. Geologists use their known rates of decay to determine the ages of rocks and geologic events through radiometric dating. |
| Graphite and diamond are both made of carbon, but only one is good for pencil lead. Why is graphite useful for this task while diamond is not? | Graphite consists of weakly bonded layers that easily slide apart and leave marks on paper. Diamond has a strong three-dimensional crystal structure, making it extremely hard and unsuitable for writing. |
| Why do some minerals form regular crystals and some do not? Even the same mineral, like quartz, may form beautiful crystals or irregular blobs. | Regular crystals form when minerals have enough time and space for atoms to arrange into well-developed crystal faces. Irregular shapes form when growth is restricted by limited space or rapid formation. |
| Why do some minerals have a fixed chemical composition and some have a range of compositions? Give an example of a mineral with a range of compositions. | Some minerals allow ions of similar size and charge to substitute for one another within their crystal structure. An example is olivine, which ranges between magnesium-rich and iron-rich compositions. |
| What is the chemical structure of all silicate minerals, and why are silicate minerals so important? | All silicate minerals are built from silicon-oxygen tetrahedra (SiO₄). Silicates are important because they make up most of Earth's crust and are the main minerals found in rocks. |
| Describe the Mohs hardness scale and list, in increasing order of hardness, the minerals of the Mohs hardness scale. | The Mohs scale compares the resistance of minerals to scratching. From softest to hardest: talc, gypsum, calcite, fluorite, apatite, feldspar, quartz, topaz, corundum, and diamond. |
| How are fracture and cleavage the same, and how are they different? | Both describe how minerals break. Cleavage occurs along flat planes of weakness in the crystal structure, while fracture produces irregular or uneven surfaces. |
| In what two ways do minerals form from magma? What types of minerals dominate the minerals that make up igneous rocks? | Minerals form when magma cools and crystallizes, and different minerals crystallize at different temperatures as cooling continues. Igneous rocks are dominated by silicate minerals such as feldspar, quartz, pyroxene, and olivine. |
| What are the three major classifications of magma? How are they defined? What elements increase or decrease in the composition of the three types? | The three types are mafic, intermediate, and felsic. They are classified mainly by silica content, with silica increasing from mafic to felsic and iron and magnesium decreasing. |
| What is viscosity? What is the effect of temperature and composition on the viscosity of magma? At the same temperature, which composition of magma will be the most viscous: felsic, intermediate, or mafic? Which will be the least viscous? | Viscosity is a fluid's resistance to flow. Higher silica content increases viscosity, while higher temperature decreases viscosity; felsic magma is the most viscous and mafic magma is the least viscous. |
| What phenomena does Bowen's reaction series help explain? | Bowen's reaction series explains the order in which minerals crystallize from magma. It also explains why different igneous rocks form and how magma composition changes during cooling. |
| Briefly explain how it is possible for a single magma to yield rocks of felsic, intermediate, and mafic composition. | As magma cools, minerals crystallize and are removed from the melt. This process changes the composition of the remaining magma, allowing different rock types to form. |
| How does mafic magma originate from ultramafic rock at a spreading ridge? | As mantle material rises beneath a spreading ridge, pressure decreases. This decompression melting produces mafic magma that later forms basalt and gabbro. |
| What causes volcanism at a subduction zone, and how does Bowen's reaction series explain the composition of the magmas there? | Water released from the subducting plate lowers the melting temperature of the mantle above it. The resulting magma rises to form volcanoes, often with intermediate to felsic compositions. |
| What is a mantle plume, and what causes one to erupt? | A mantle plume is a column of unusually hot mantle rock rising toward the surface. As it reaches lower pressures near the surface, melting occurs and volcanic activity results. |
| What two types of volcanic features result from volcanism above a mantle plume? How are hot spots related to plate boundaries? | Mantle plumes commonly form shield volcanoes and volcanic island chains. Hot spots are usually located away from plate boundaries and record plate movement over the plume. |
| Why does Bowen's reaction series predict that mafic intrusive rocks should be much more common than felsic intrusive rocks? | Mafic minerals crystallize first and are abundant in magma produced from the mantle. Therefore, Bowen's reaction series suggests mafic intrusive rocks should be widespread |
| Briefly explain why felsic intrusive rocks are actually more common than mafic intrusive rocks. | Continental crust promotes melting, differentiation, and assimilation that produce felsic magmas. These magmas often cool slowly underground and form large bodies of granite. |
| What are the effects of assimilation on magma composition? | Assimilation occurs when magma melts and incorporates surrounding rock. This usually changes the magma toward a more felsic composition. |
| What are the effects of magma mixing on magma composition? | When two magmas mix together, their compositions combine. The resulting magma often has an intermediate composition between the two original magmas. |
| What are aphanitic and phaneritic textures, and what do they say about the way the rock formed? | Aphanitic rocks are fine-grained because they cooled rapidly at or near the surface. Phaneritic rocks are coarse-grained because they cooled slowly underground. |
| How are basalt and gabbro similar, and how are they different? How about andesite and diorite? Rhyolite and granite? How are basalt, andesite, and rhyolite the same, and how are they different? How about gabbro, diorite, and granite? | Each pair has the same composition but different textures. Basalt, andesite, and rhyolite are volcanic rocks, while gabbro, diorite, and granite are intrusive rocks. |
| What are pegmatites, and how do they form? | Pegmatites are extremely coarse-grained igneous rocks. They form from water-rich magma during the final stages of cooling, allowing very large crystals to grow. |
| What are dikes, sills, and laccoliths? | A dike cuts across existing rock layers, while a sill forms parallel to them. A laccolith is a dome-shaped intrusion that pushes overlying layers upward. |
| Briefly explain batholith formation. | Batholiths form when many large bodies of magma intrude and cool deep underground. Over time, erosion exposes these massive intrusive rock bodies. |
| When looking at a hand sample of an igneous rock, how would you tell if it is plutonic or volcanic? | Plutonic rocks have large visible crystals because they cooled slowly underground. Volcanic rocks have fine crystals or glassy textures because they cooled rapidly at the surface |
| How do volcanic necks form? | Magma solidifies inside the central vent of a volcano. Later erosion removes the surrounding rock, leaving the hardened magma exposed. |
| What is volcanism, and what types of rocks does it produce? | Volcanism is the eruption of magma onto Earth's surface. It produces extrusive igneous rocks such as basalt, andesite, and rhyolite, along with volcanic ash deposits. |
| What are the reasons that volcanism is primarily a constructive process? | Volcanism creates new crust and builds landforms such as islands, lava plateaus, and volcanic mountains. It adds material to Earth's surface rather than removing it. |
| How is the behavior of gases different in a quiet and an explosive eruption? | In quiet eruptions, gases escape gradually from low-viscosity magma. In explosive eruptions, gases become trapped in viscous magma, causing pressure to build until it is released violently. |
| How do columnar joints form? | As lava cools and contracts, it cracks in a regular pattern. These cracks commonly form polygonal columns, especially in basalt flows. |
| Mauna Loa volcano in Hawaii is huge and has gentle slopes; Mount Rainier in Washington; and Paricutin in Mexico steeper composed of loose pyroclastic material. What type of volcano does each one represent, and what kind of volcanic activity produced it? | Mauna Loa is a shield volcano formed by fluid basaltic lava flows. Mount Rainier is a composite volcano, while Paricutin is a cinder cone built from loose pyroclastic material. |
| How are cinder cones different from the other two major types of volcanoes? | Cinder cones are small, steep-sided volcanoes made mainly of loose volcanic fragments. They usually form quickly and have relatively short lifespans. |
| Describe composite volcanoes. How do they differ from shield volcanoes and cinder cones? | Composite volcanoes consist of alternating layers of lava and pyroclastic material. They are steep-sided volcanoes that commonly produce explosive eruptions. |
| Briefly explain how magma can originate at spreading zones if temperatures at such shallow depths cannot alone produce melting. | As mantle rock rises beneath spreading centers, pressure decreases. This decompression melting allows magma to form even without an increase in temperature. |
| Describe igneous activity at convergent plate boundaries. | At convergent boundaries, water released from the subducting plate causes melting in the mantle. The resulting magma rises to form volcanic arcs and intrusive igneous bodies. |
| Briefly explain how exfoliation domes form. | When overlying rock is removed by erosion, pressure on the underlying rock decreases. The rock expands and fractures in sheets that peel away, forming dome-shaped structures. |
| Briefly explain why water is such an important agent in chemical weathering. | Water dissolves minerals and allows chemical reactions to occur. It also transports dissolved ions, making weathering processes much more effective. |
| Briefly explain how hydrolysis results in the weathering of some minerals. | Hydrolysis occurs when water reacts chemically with minerals and changes them into new minerals. For example, feldspar can be altered into clay minerals through hydrolysis. |
| Explain why the ferromagnesian minerals most susceptible to chemical weathering are those formed early in the continuous branch of Bowen's reaction series. | Minerals that crystallize at high temperatures are least stable at Earth's surface conditions. As a result, olivine and pyroxene weather more quickly than minerals such as quartz. |
| Explain why and give two examples of how climate is more effective in determining soil type than is parent rock type | Climate controls the amount of weathering, leaching, and organic activity in soil formation. For example, tropical climates produce deeply weathered soils, while arid climates produce thin soils regardless of the parent rock. |
| How do detrital sedimentary rocks differ from chemical sedimentary rocks? | Detrital sedimentary rocks form from fragments of pre-existing rocks that are compacted and cemented together. Chemical sedimentary rocks form when dissolved minerals precipitate from water. |
| Briefly explain why the study of sedimentary environments is important in the study of historical geology. | Sedimentary environments provide clues about past conditions such as climate, water depth, and depositional settings. They help geologists reconstruct Earth's history. |
| Briefly explain how coal forms. | Coal forms from the accumulation of plant material in swampy environments. Burial, compaction, and heat gradually transform the organic material into coal. |
| Explain how fossils, and especially microfossils, can be used to help determine ancient depositional environments. | Different organisms live in specific environments and conditions. Finding their fossils allows geologists to determine characteristics such as water depth, salinity, and climate. |
| What are some ways in which fossils are useful? | Fossils provide evidence of past life and evolution. They are also used to date rocks and correlate rock layers between different locations. |
| What is the role of heat as an agent of metamorphism? What are the heat sources available for the creation of metamorphic rocks? | Heat causes minerals to recrystallize and become stable under new conditions. It can change both the texture and mineral composition of a rock. |
| What are the sources of the heat, pressure, and fluids that cause rocks to metamorphose? | Heat comes from magma and deep burial, pressure comes from tectonic forces and overlying rock, and fluids come from groundwater or hot fluids released during metamorphism. Together these factors alter rocks. |
| Why is time important to metamorphic processes? | Metamorphic changes occur slowly and require long periods of time. The longer rocks are exposed to heat and pressure, the more extensive the changes can be |
| What features would you look for to see if a metamorphic rock had undergone lithostatic or differential pressure? | ithostatic pressure produces uniform compression and usually no preferred mineral orientation. Differential pressure aligns minerals and produces foliation or banding. |
| Is it always possible to identify the parent rock when looking at a metamorphic rock? Why or why not? | No. Intense metamorphism can completely change a rock's texture and mineral composition. This may destroy evidence of the original parent rock. |
| Describe how contact metamorphism occurs. What are the important factors that cause rocks to alter in this type of metamorphism? | Contact metamorphism occurs when hot magma intrudes surrounding rocks. Heat is the main factor causing changes, while pressure usually plays a minor role. |
| Describe regional metamorphism. Where does it take place? | Regional metamorphism affects large areas and results from heat and pressure during mountain building. It commonly occurs at convergent plate boundaries. |
| What are index minerals, and what are they used for? Give an example of minerals that would be found in a low-grade, intermediate, and high-grade metamorphosed shale. | Index minerals form under specific temperatures and pressures. Geologists use them to determine the metamorphic grade of rocks. Low-grade shale: chlorite Intermediate-grade shale: biotite or garnet High-grade shale: sillimanite |
| What is metamorphic grade, and present an example of how a rock reaches its metamorphic grade? | Metamorphic grade describes the intensity of metamorphism experienced by a rock. As a shale is subjected to increasing heat and pressure, it may change from slate to phyllite to schist to gneiss. |
| How are metamorphic rocks classified? What are the two main classifications, and how are they different from each other? | Metamorphic rocks are classified by texture and mineral composition. The two main groups are foliated and nonfoliated rocks. |
| How are foliated metamorphic rocks classified? Describe some of the rock types found at different grades of foliated metamorphic rocks. | Foliated rocks are classified according to texture and metamorphic grade. Common examples are slate, phyllite, schist, and gneiss from lowest to highest grade. |
| Describe nonfoliated metamorphic rocks. What is their appearance? Describe the two types of nonfoliated metamorphic rocks. | Nonfoliated rocks lack layers or banding because minerals are not aligned. They commonly consist of interlocking crystals, such as marble and quartzite |
| Describe the characteristics of marble. How does it form, and what is it used for? | Marble is a nonfoliated rock formed by the metamorphism of limestone. It is commonly used as a building stone and for sculptures. |
| What is a metamorphic facies, and how are metamorphic facies named? | A metamorphic facies is a group of minerals formed under specific temperature and pressure conditions. Facies are named after characteristic mineral assemblages. |
| What are metamorphic zones based on? How are rocks within the same metamorphic zone similar to each other? | Metamorphic zones are based on the first appearance of specific index minerals. Rocks within the same zone experienced similar metamorphic conditions. |
| Describe the occurrence of metamorphism along an oceanic-continental convergent plate boundary | Metamorphism occurs as rocks are buried, compressed, and heated during subduction. High-pressure metamorphic rocks commonly form near the subduction zone. |
| Describe the occurrence of metamorphism along a divergent plate boundary | Hot magma and circulating hydrothermal fluids alter rocks near spreading centers. This produces low-pressure metamorphism and hydrothermal alteration. |
| What are some uses of metamorphic rocks, such as marble, slate, sulfide ore, talc, graphite, and clay? | Marble is used in construction and sculpture, slate is used for roofing, talc is used in powders, graphite is used in pencils, clay is used in ceramics, and sulfide ores provide valuable metals. |
| How do metamorphic processes form ore deposits? What are some of the ores that are formed? | Hot fluids can transport and concentrate metals within rocks during metamorphism. Important ores formed this way include gold, copper, lead, zinc, and silver deposits. |
| What is an earthquake? What are aftershocks? | An earthquake is the sudden release of energy caused by movement along a fault. Aftershocks are smaller earthquakes that occur after the main event as rocks continue adjusting. |
| How does elastic rebound theory explain when earthquakes occur? | Stress gradually builds in rocks until they break and move along a fault. The stored energy is then released as seismic waves. |
| Describe what seismographs do and how they work. | Seismographs detect and record ground motion caused by earthquakes. A suspended mass remains relatively stationary while the ground moves beneath it. |
| What causes earthquakes? | Earthquakes occur when stress exceeds the strength of rocks and movement occurs along a fault. Most are caused by tectonic plate motion. |
| What happens along an earthquake fault after rupturing begins? How is the length of time of ground shaking related to the length of the fault? | Once rupture begins, movement spreads along the fault and releases stored energy. Longer faults generally produce longer periods of ground shaking. |
| Describe the three categories of earthquakes based on focal depth and what causes them. | Shallow-focus earthquakes occur less than 70 km deep and are most common. Intermediate-focus earthquakes occur between 70 and 300 km, while deep-focus earthquakes occur between 300 and 700 km and are associated with subduction zones. |
| Why do most earthquakes occur along the circum-Pacific belt? | The circum-Pacific belt contains many active plate boundaries, especially subduction zones. These areas experience frequent tectonic activity and fault movement. |
| What are the differences between P-waves and S-waves? | P-waves are compressional waves that travel through solids and liquids and move fastest. S-waves are shear waves that travel only through solids and arrive later. |
| Describe surface waves and their most important two types. | Surface waves travel along Earth's surface and cause the greatest damage. The two main types are Love waves and Rayleigh waves. |
| What is earthquake intensity, how is it measured, and what factors are involved in the intensity of a quake? | Intensity measures the effects and damage caused by an earthquake at a specific location. It is commonly described using the Modified Mercalli Intensity Scale. |
| What causes tsunamis, and why are they so destructive? | Tsunamis are caused by sudden displacement of large volumes of water, usually by undersea earthquakes. They are destructive because they can travel long distances and produce large coastal floods. |
| What happens to P- waves and S-waves when they encounter the core-mantle boundary, and what does this change in behavior indicate about the core? | P-waves slow down and bend when entering the outer core. S-waves cannot travel through the liquid outer core, indicating that the outer core is liquid |
| Compare the continental crust with oceanic crust in terms of composition and thickness. | Continental crust is thicker, less dense, and mainly granitic in composition. Oceanic crust is thinner, denser, and mainly basaltic. |
| What is deformation, and what causes it? | Deformation is the change in shape, position, or volume of rocks. It is caused by stress from tectonic forces such as compression, tension, and shear. |
| Why is the study of deformation and deformed rock important? | It helps geologists understand how mountains, faults, and folds form. It also helps interpret Earth's tectonic history. |
| What are stress and strain? How are they related to deformation? | Stress is the force applied to rocks, while strain is the resulting change in shape or volume. Strain is the response to stress. |
| What are the three types of stress, and how do they affect rocks? | Compression squeezes rocks together, tension pulls them apart, and shear causes rocks to slide past each other. |
| What happens first when a stress is applied to a rock? What two things could happen if the stress continues to the next step? | The rock first deforms elastically, meaning it temporarily changes shape. If stress continues, it may either fracture (brittle failure) or flow (ductile deformation). |
| What factors are involved for a rock to behave as a brittle substance, and what factors cause it to behave plastically? | Low temperature, low pressure, and fast stress cause brittle behavior. High temperature, high pressure, and slow stress cause ductile behavior. |
| If you observe steeply inclined sedimentary rocks, what can you conclude? | They indicate that the rocks have been tilted or folded after deposition. They were originally deposited horizontally. |
| What is strike? What is dip? How are they measured in rock layers? | Strike is the compass direction of a horizontal line on a rock layer. Dip is the angle and direction the rock layer tilts downward. |
| How can you tell a dome from a basin? | In a dome, rock layers dip outward from the center. In a basin, rock layers dip inward toward the center. |
| How can you tell if a strike-slip fault is right- or left-lateral? | Stand on one side of the fault and observe movement of the other side. If it moves right, it is right-lateral; if it moves left, it is left-lateral. |
| What is an orogeny? What does a theory of orogeny need to explain? | An orogeny is a mountain-building event caused by plate convergence. It involves deformation, metamorphism, and uplift of crust. |
| Describe the plate tectonics processes and associated stresses that have led to the formation of the Himala the world's largest mountain range? | The Himalayas formed from the collision of the Indian and Eurasian plates. Compression caused crustal thickening and uplift. |
| How do continents grow? What material is added to them and how? | Continents grow by accretion of volcanic arcs, sediment deposits, and fragments of crust. These materials are added at convergent boundaries. |
| Briefly explain why, according to the principle of isostasy, continental crust floats higher than oceanic crust. | Continental crust is less dense than oceanic crust. Because of isostasy, it “floats” higher on the mantle. |
| What is isostatic rebound? Give an example | Isostatic rebound is the rise of land after the removal of heavy weight such as ice sheets. Example: parts of Canada are still rising after the last ice age. |
| If the mantle transmits S-waves, then how can it behave like a liquid, as implied by the principle of isostasy? | The mantle is solid but can flow slowly over long time scales. It behaves like a plastic solid, allowing isostatic adjustment. |
| Why does continental crust stand higher than oceanic crust? | It is thicker and less dense than oceanic crust. This causes it to float higher on the mantle. |
| What is shear strength? What factors collectively define a slope's shear strength? | Shear strength is the resistance of a slope to sliding failure. It depends on material strength, friction, and cohesion. |
| How does gravity affect a slope? | Gravity pulls material downslope, driving mass wasting and erosion. Steeper slopes experience stronger gravitational stress. |
| What are some ways by which a slope can become oversteepened? How can oversteeping cause mass wasting? | Oversteepening can occur through erosion, undercutting by rivers or waves, or human activity. This reduces stability and can trigger landslides. |
| What role does weathering play in mass wasting? | Weathering breaks down rock and weakens slope materials. This makes slopes more prone to failure and movement. |
| What factors contribute to mass wasting in tropical versus arid and semiarid climates? | Wet climates promote landslides due to saturation. Dry climates promote rockfalls due to lack of vegetation and loose material. |
| Briefly explain why saturated clay is a very unstable slope material. | Water reduces friction between particles in clay. This causes it to behave like a fluid and slide easily. |
| How does vegetation affect slope stability? What happens if vegetation is removed from the slope? | Vegetation stabilizes slopes by binding soil with roots and absorbing water. Removing vegetation increases erosion and landslide risk. |
| How does the geology (dip of rock layers or joints) on a slope affect slope stability? | If rock layers dip in the same direction as a slope, failure is more likely. Joints and fractures also create planes of weakness. |
| Compare and contrast rapid mass movements and slow mass movements. | Rapid movements happen suddenly (landslides, rockfalls). Slow movements occur gradually over time (creep). |
| Compare and contrast mudflows, debris flows, and earthflows. | Mudflows are fast-moving water-rich flows of fine sediment. Debris flows contain larger rock fragments. Earthflows are slower, viscous movements of fine material. |
| What is permafrost, and what problems are associated with construction in a permafrost environment? | Permafrost is permanently frozen ground. It causes construction problems because thawing leads to ground instability. |
| How can areas with high potential for slope failure be identified? | Geologists study slope angle, rock type, water content, and past landslide history. These factors help predict instability. |
| What is the effect of reducing water on a slope to mass movements? How can this be done? | Removing water increases friction and stability. Drainage systems are often used to reduce landslide risk. |
| Describe the hydrologic cycle | Water circulates between oceans, atmosphere, land, and groundwater through evaporation, condensation, precipitation, and runoff. |
| What are braided streams, and where do they form? | Braided streams are river systems with multiple shifting channels. They form where sediment load is high and flow is variable. |
| What causes a stream to meander? | Meanders form due to erosion on outer bends and deposition on inner bends. This causes the river to curve over time. |
| What happens when a stream overflows its banks? | Flooding occurs and sediment is deposited on floodplains. This builds fertile soils. |
| How and where do alluvial fans form? | Alluvial fans form where a fast-moving stream slows suddenly on a flat surface. Sediment is deposited in a fan shape. |
| Describe the major drainage patterns. | Drainage patterns include dendritic (tree-like), trellis (folded terrain), radial (volcanoes), and rectangular (faulted rocks). |
| Describe the evolution of valleys. | Valleys begin as narrow V-shaped features formed by erosion. Over time they widen and deepen as erosion continues. |
| Briefly explain how a meandering stream can become incised in solid bedrock. | Uplift of land or drop in base level causes the river to cut downward. The meandering pattern becomes preserved in bedrock. |
| What is the immediate source of the water in groundwater? | Groundwater comes from precipitation that infiltrates into the ground. It moves downward through soil and rock until it reaches saturated zones. |
| Why are porosity and permeability important to groundwater? | Porosity is the amount of open space in rock, and permeability is how easily water flows through it. Together they control how much groundwater a rock can store and transmit. |
| How can limestone be dissolved by groundwater when it is almost insoluble in pure water? How does this happen? | Groundwater becomes slightly acidic when it absorbs carbon dioxide, forming weak carbonic acid. This acid dissolves limestone over time, creating caves and karst features. |
| What are hot springs, and what are the sources of heat? | Hot springs are natural discharges of heated groundwater at Earth’s surface. The heat usually comes from magma or from deep circulation of water in the crust. |
| What are glaciers? How are they as agents of erosion and deposition? | Glaciers are large, slow-moving masses of ice. They erode by plucking and abrasion and deposit sediments called till. |
| Describe valley glaciers. | Valley glaciers are rivers of ice that flow downhill through mountain valleys. They erode U-shaped valleys as they move. |
| How do continental glaciers differ from valley glaciers? | Continental glaciers cover large land areas and spread outward in all directions. Valley glaciers are confined to mountain valleys. |
| What is the difference between ice caps and continental glaciers? | Ice caps are smaller ice sheets that cover less than 50,000 km². Continental glaciers are much larger and can cover entire continents. |
| How and where do glaciers form? | Glaciers form where snow accumulation exceeds melting over long periods. This usually occurs in polar regions or high mountain elevations. |
| Describe the main way that glaciers move. In which situations is this essentially the only type of flow a glacier will undergo? | Glaciers mainly move by internal deformation, where ice crystals slowly shift and flow under pressure. |
| What is the lesser way that glaciers flow, and what facilitates this movement? In which type of glaciers is this flow more important? | Glaciers also move by basal sliding, where meltwater at the base allows the glacier to slide over bedrock. This is more important in warmer glaciers. |
| Under what conditions do large crevasses develop in glaciers? What forces act to produce them, and where in the glacier are they found? What happens if a glacier descends over a steep precipice? | Crevasses form when the glacier’s surface is under tension as it moves over uneven terrain. They are common near the top and edges of glaciers. |
| What conditions are needed for glaciers to form and be maintained? As a result of these conditions, where are glaciers found? | Cold temperatures and high snowfall are required so accumulation exceeds melting. Glaciers form in polar regions and high mountains. |
| What are the zone of accumulation, zone of wastage, and fir limit? | The accumulation zone gains snow, the wastage zone loses ice, and the firn line separates the two areas. |
| Under what conditions will the fin limit remain the same from year to year? Under what conditions will it change? What happens if the fir limit moves upward year after year? | If accumulation equals melting, the firn line stays stable. If melting increases, the firn line rises; if accumulation increases, it lowers. |
| Describe the conditions that would make a valley glacier flow faster. | Steeper slopes, thicker ice, and higher temperatures increase glacier flow speed. |
| Describe differences in flow rates within a valley glacier | Ice flows faster in the center and top of the glacier and slower along the sides and bottom due to friction. |
| What evidence of their passage do glaciers leave on bedrock? | Glaciers leave striations (scratches), polished rock surfaces, and U-shaped valleys. |
| What is glacial drift, and how does it differ from glacial till? | Glacial drift is all sediment deposited by glaciers. Till is unsorted material deposited directly by ice. |
| What are the different types of moraines: end moraines, ground moraines, recessional moraines, lateral moraines, and medial moraines? | End moraines form at glacier edges, lateral moraines along sides, medial moraines in the center, ground moraines beneath ice, and recessional moraines during pauses in retreat. |
| Explain the origin of varves and their significance in the chronologies of glacial lake deposits. | Varves are annual layers of sediment in glacial lakes. They help scientists determine past climate and glacial history. |
| Describe sediment transport as bed load, including saltation. | Bed load is sediment moved along the river or ground surface. Saltation is the bouncing movement of sand-sized particles. |
| Briefly explain why sand is moved by wind before clay and silt during wind erosion. | Wind lifts sand more easily because it is heavier than silt but not cohesive like clay. Clay sticks together due to moisture and cohesion. |
| Why do dunes form? How are they self-generating? | Dunes form when wind deposits sand in areas where wind velocity decreases. They grow as wind continuously moves sand up the gentle slope. |
| How do dunes build their characteristic asymmetrical profile? | Wind pushes sand up the gentle windward side. Sand then avalanches down the steep slip face. |
| What type of weathering is dominant in deserts and why? What about other types of weathering? | Mechanical weathering dominates due to temperature changes and lack of water. Chemical weathering is slower but still occurs in limited moisture. |
| What are alluvial fans, and why are they common in desert mountain ranges? | Alluvial fans form where streams leave steep mountains and spread onto flat desert basins, depositing sediment quickly. |
| What is relative dating, and what can it tell us? | Relative dating determines the order of events without giving exact ages. It uses principles like superposition and cross-cutting relationships. |
| What is absolute dating, and what is it based on? What can absolute dating tell us? | Absolute dating gives numerical ages using radiometric methods. It determines how many years have passed since a rock formed. |
| What is the principle of uniformitarianism? Why does the principle of uniformitarianism lead to the conclusion that Earth's age is great? | Uniformitarianism states that present-day geological processes operated in the past. This suggests Earth is very old because processes take long times to create large features. |
| What is the principle of superposition, and what is its importance? Who is credited with discovering it? | In undeformed sedimentary layers, the oldest rocks are at the bottom and the youngest at the top. It was developed by Steno. |
| What is the principle of fossil succession, and what is its importance? Who is credited with discovering it? | Fossils appear in a consistent vertical order in rock layers. William Smith used this principle to correlate rock layers. |
| What do unconformities represent? | Unconformities represent gaps in the geologic record caused by erosion or lack of deposition. |
| What are the three types of unconformities, and what is each missing? | Angular unconformity: tilted layers below flat layers Disconformity: missing time between parallel layers Nonconformity: sedimentary rock over igneous/metamorphic rock |
| Why is correlation needed to construct a complete geologic history of a region? How does correlation work, eg., in the Colorado Plateau region? | Correlation links rock layers from different locations. It helps build a complete geologic history of a region. |
| How do geologists do correlation using rocks and fossils? | Geologists match rock types, fossil content, and age data between different areas to identify equivalent layers. |
| If you start with an element with 1,000,000 parent atoms, how many parents and how many daughters will there be after 6 half-lives? | After 6 half-lives: 1,000,000 → 15,625 parent atoms remain, and 984,375 daughter atoms form. |
| Why do igneous rocks yield the most accurate radiometric ages, and what is the calculated date the actual age of? | Igneous rocks form from molten material, resetting the radiometric clock. The date reflects when the rock solidified. |
| What is a closed system, and why is it necessary for a rock or mineral being dated to be a closed system? What is the result if it is not a closed system? | A closed system does not gain or lose parent or daughter isotopes. If it is not closed, the age is inaccurate. |
| Why are metamorphic rocks difficult to date accurately? | Metamorphism can reset or disturb radioactive clocks. This makes it difficult to determine the original formation age. |
| What is carbon-14 dating useful for in terms of age and type of sample? | It is used to date recent organic material up to about 50,000 years old, such as bones or wood. |
| Why do we know very little about the planet's first 600 million years? Why do we know only slightly more about the early part of the Precambrian? | Early rocks have been destroyed by erosion, subduction, and metamorphism. This removes most evidence from Earth’s earliest history. |
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