Q&A Hero

Q: Match the type of motion with the correct definition. A) Detached material moves in a free-fall B) Material moves downslope as a viscous fluid C) Mass movements in which there is a distinct plane of weakness between the slide material and underlying stable material 1. Fall 2. Slide 3. Flow

Q: Why won't meltwater infiltrate into permafrost?

Q: How do both weathering and erosion work together to produce significant landforms such as broad valleys?

Q: Creep is the most widespread mass-wasting process.

Q: Tilted retaining walls are a sign of a landscape undergoing creep.

Q: Solifluction occurs during the warmer months of the melt season.

Q: Fast mass-wasting processes are more widespread than slow mass-wasting processes.

Q: Slow forms of mass wasting such as creep and solifluction are considered slow because they are restricted to gentle slopes and cannot achieve a high velocity.

Q: Mudflows are big enough to move in any direction, regardless of the orientation of the landscape.

Q: Rockfalls are the primary way in which talus slopes are built and maintained.

Q: Creep is a slow type of mass wasting that moves at a rate of a few centimeters per year.

Q: Thick deposits of soil over bedrock are more stable than thin deposits over bedrock.

Q: Grasses will result in more slope stability than trees.

Q: The weathering process of frost action can make a slope less stable.

Q: Postfire debris flows are most common in the first 2 years after a fire.

Q: Rapid mass-wasting events do not always need a trigger.

Q: Low, old, rounded terrain is actively undergoing mass wasting.

Q: Mass wasting is possible only with the aid of a transportation agent such as water, wind, or ice.

Q: Which location is likely to experience creep? A) Horizontal plateaus B) Steep slopes C) Gentle slopes D) Steep and gentle slopes E) Vertical cliffs

Q: One main cause of creep is A) melting of ice during a volcanic eruption. B) oversteepening of a slope due to construction. C) expansion and contraction of soils during freezing and thawing. D) collapse due to weight of intense rains saturating the sediment.

Q: In what climate(s) is solifluction prevalent? A) Topics B) Tundra and subarctic C) Arid D) Temperate and humid

Q: Which factor exerts the greatest control over the velocity of debris flows and the distance they will travel? A) Debris content B) Water content C) Slope angle D) Vegetation

Q: Which of the following scenarios best describes the creation of the lahars associated with the eruption of Mt. St. Helens in 1980? A) Hot gases melted the volcano's snowcap, generating meltwater that mixed with ash. B) A volcanic flank collapsed in a landslide, which flowed into Spirit Lake. C) Ash deposited during the eruption was remobilized by a flood years later. D) The eruption deposited fine ash in the Toutle River.

Q: Which rapid form of mass wasting is found at the base of slump blocks? A) Debris flow B) Rockslide C) Lahar D) Earthflow

Q: The creation of which sedimentary feature is controlled in part by debris flows exiting a narrow canyon? A) Fluvial B) Dunes C) Lacustrine D) Alluvial fan

Q: What combination of factors was responsible for the disaster west of Yellowstone National Park on August 17, 1959? A) Rock falls filled a lake with debris until the water overtopped the dam and eroded through the concrete. B) Water migrating along foliation layers in the metamorphic rock destabilized a dam, which collapsed and flooded the valley. C) A severe earthquake triggered a slide that blocked a river and flooded a campground. D) Drainage from the reservoir generated a lahar, which destroyed small towns downstream.

Q: Which mass wasting process involved volcanically derived material from the eruption of Nevado del Ruiz and destroyed the city of Armero in 1985? A) Lahar B) Rockfall C) Solifluction D) Debris flow

Q: Which scenario led to the disaster that destroyed the city of Armero in 1985? A) Heavy rains saturated the slopes of Nevado del Ruiz. B) Flooding eroded the slope of Nevado del Ruiz, oversteepening it. C) An earthquake shook the slope materials of Nevado del Ruiz loose, causing a landslide. D) Heat from the eruption of Nevado del Ruiz melted the volcano's ice cap.

Q: Which would be the most likely location for a rockslide to occur? A) Rock cliff with no fractures or voids B) Inclined strata with joints and fractures parallel to the slope face. C) A soil-covered slope with a stream flowing at the base D) Bottom of a stream valley with a highly meandering stream

Q: What is the crescent-shaped mark found at the top of a slump block? A) Scarp B) Ditch C) Overburden D) Earthflow

Q: A ________ is an example of a translational slide. A) rockslide B) creep C) mudflow D) slump

Q: A ________ is an example of a rotational slide. A) rockslide B) fall C) mudflow D) slump

Q: What is the slowest form of mass wasting? A) Slump B) Debris flow C) Creep D) Earthflow

Q: Why is it possible for rock avalanches to move at speeds in excess of 200 kilometers per hour? A) They are moving with large quantities of water. B) They are moving with molten material such as lava. C) They are moving with large quantities of air trapped and compressed beneath the debris. D) They are moving with large chunks of ice compressed beneath the moving material.

Q: What is the fastest form of mass wasting? A) Slide B) Slump C) Creep D) Rock avalanche

Q: A ________ slide is a type of mass wasting process where a mass of material moves along relatively flat surfaces such as joints, faults or bedding planes. A) translational B) fall C) rotational D) horizontal

Q: A ________ slide is type of mass wasting process where the surface of rupture is a concave-upward curve and descending material exhibits downward and outward motion. A) translational B) fall C) rotational D) horizontal

Q: Which type of motion will supply material to and maintain talus slopes? A) Flow B) Fall C) Slide D) Slump

Q: Southern California is famous for its wildfires, which are often exacerbated by the Santa Ana winds blowing through the canyons. What mass wasting event will later devastate the same fire-affected areas? A) Mudflows B) Rockslides C) Slumps D) Solifluction

Q: What are three examples of preexisting slip planes for translational slides? A) Slumps, valleys, and mudslides B) Bedding planes, frost wedging, and permafrost C) Faults, bedding planes, and joints D) Water, ice, and crevasses

Q: How is it possible for a landslide to occur without a trigger? A) Heating from geothermal processes weakens the rock. B) Long-term weathering weakens the rock past the strength necessary to maintain stability. C) Slopes are shaken by earthquakes and the materials are loosened. D) Water migrates along the sediment particles, reducing friction between them.

Q: Which slope composition is the most stable? A) Unconsolidated sediments B) Rock layers inclined parallel to the slope C) Solid bedrock D) Carbonate rock affected by dissolution

Q: Which of the following mass wasting disasters was triggered by an earthquake? A) Storm King Mountain, Colorado, 1994 B) Colorado Front Range, Colorado, 2013 C) Chengdu, China, 2008 D) Oso, Washington, 2014

Q: Which of the following is not a way an earthquake can trigger mass wasting? A) Shaking will harden the soils at the surface, which repels flowing water. B) Shaking creates a landslide. C) Liquefaction caused sediments to behave like fluids and move. D) Shaking has created rock falls that have blocked canyons, an effect that will lead to later problems during flash floods.

Q: Which of the following will not oversteepen a slope and lead to mass wasting? A) Quarrying B) Coastal erosion C) Construction D) None of these

Q: A stream is cutting into a valley wall. Which of the following is the most likely trigger for a mass wasting event? A) The stream will saturate the slope and generate a mudflow. B) The stream erodes the toe of the slope, which results in the slope becoming oversteepened. C) Upslope trees will be removed, reducing slope strength. D) The stream will deposit extra sediment on the slope, increasing the weight on the slope.

Q: A stream is flowing over a hill covered in thick soil. The stream is eventually blocked to create a small pond in order to free land downhill for construction. What will ultimately happen to the strength and cohesion of the soil in the area around this pond? A) Strength and cohesion will decrease. B) Strength and cohesion will increase. C) Strength will decrease and cohesion will increase. D) Neither will be affected.

Q: What is the angle of repose for a sediment such as sand? A) 7 B) 12 C) 33 D) 59

Q: A piece of gravel is resting on a slope. Which of the following best describes how the gravitational force pulling the gravel downward will vary with the inclination of the slope? A) Gravitational force is not affected by the slope angle. B) Gravitational force will increase as the slope angle decreases. C) Gravitational force will only change with the addition of water. D) Gravitational force will decrease as the slope angle decreases.

Q: Which sediment size has the steepest angle of repose? A) Gravel B) Sand C) Silt D) Clay

Q: What is the angle of repose? A) The angle of the slip plane from a slide B) The steepest angle at which a material remains at rest C) The angle of an inclined rock layer measured from a horizontal line D) The angle of plunge into the interior

Q: Which of the following scenarios would lead to a mass wasting event due to an oversteepened slope? A) Trees are planted on a slope B) Heavy rains saturate slope materials C) Construction of buildings on slopes D) Baking of surface materials during a wildfire

Q: A ________ is not the sole cause of a mass wasting event, but the last of many causes that initiate the downslope movement of materials. A) debris flow B) slide C) repose angle D) trigger

Q: Which of the following was the cause of the debris flow in Oso, Washington, in March 2014? A) Volcanic eruptions generated a lahar. B) A stream at the base of a slope eroded the toe of the slope away. C) Heavy rains saturated the surface materials on the slope. D) The slope was oversteepened during construction.

Q: What is the controlling force of mass wasting? A) Water B) Gravity C) Friction D) Hydration

Q: Which region would be most likely to produce a catastrophic landslide? A) Old, eroded, worn-down mountains B) V-shaped stream valley with gentle slopes C) Flat-lying floodplains along a stream D) Steep, geologically young mountains

Q: Stream valleys are produced through combined effects of mass wasting and running water. If running water alone were responsible for creating stream valleys, how would they appear? A) Wide valleys with flat bottoms B) V-shaped valleys C) Narrow valleys with vertical walls D) U-shaped valleys

Q: Which of the following factors does not influence mass wasting? A) Gravity B) Geologic age C) Water D) Vegetation

Q: Which of the following locations would be most likely to see large-scale, rapid mass wasting? A) Florida Everglades B) Central Illinois C) Mojave Desert D) The Rocky Mountains

Q: What nongeologic term is commonly used to describe a sudden event in which large volumes of material move down steep slopes? A) Mass Wasting B) Carbonization C) Landslide D) Lahar

Q: ________ is the downslope movement of rock, regolith, or soil under the direct influence of gravity. A) Mass wasting B) Erosion C) Weathering D) Dissolution

Q: What kind of mountains are visible in this image? A) Fault-block mountains B) Volcanic arc C) Collisional mountains D) Accreted terranes

Q: What geologic body is marked in this image by the circle? A) Batholith B) Accreted terrane C) Oceanic lithosphere D) Flood basalts

Q: What kind of volcanic chain is present in this image? A) Hot spot volcanoes B) Volcanic island arc C) Continental volcanic arc D) Rift volcanoes

Q: Notice the part of this image labeled "continued trench rollback." What is happening in "trench rollback"? A) Old, dense lithosphere sinks, creating slab suction that pulls the upper plate toward the trench. B) Continued tension on the plate results in rifting, dropping blocks of continental crust. C) The trench gets deeper as the descending plate locks against the overriding plate and pulls it down. D) Rising magma plutons melt the base of the lithosphere to create a depression.

Q: What kind of stress would be affecting the marked region in this image? A) Compression B) Tension C) Shear

Q: Which part of the subduction zone is indicated in this image? A) Deep-ocean trench B) Forearc basin C) Volcanic arc D) Back-arc basin

Q: Explain the most widely accepted hypothesis behind the formation of the Basin and Range Province. When was this process supposed to be occurring?

Q: Is there data to suggest there was more accretion in the distant past (4 billion years ago) or the more recent past (50 million years ago)? Explain.

Q: How can plate tectonics help explain the existence of fossil marine organisms in rocks found on top of compressional mountains?

Q: How does an Andean-type mountain-building event compare to a Cordilleran-type? Consider tectonic environments as well as processes of formation.

Q: Compare and contrast the formation of a primary magma to that of a secondary magma. How does each form?

Q: Match the geologic location with the type of mountain building. Please note that your choices may be used more than once. A) Fault-block mountain building B) Andean-type mountain building C) Alpine-type mountain building D) Cordilleran-type mountain building E) Island arc-type mountain building 1. Sierra Nevada Mountains 2. Himalayan Mountains 3. North American Cordillera 4. Basin and Range Province 5. The Alps 6. Teton Range 7. Japanese Archipelago

Q: Match the features of a subduction zone with the manner of formation. A) Where pyroclastic materials and sediments eroded from landmasses collect on the opposite side of the island arc from the trench B) Where pyroclastic materials and sediments eroded from landmasses collect between the island arc and the trench C) Partial melting of subducting plates create magma, which rises to the surface D) Where the subducting slabs of oceanic lithosphere descend into the asthenosphere 1. Volcanic arc 2. Deep-ocean trench 3. Fore-arc region 4. Back-arc region

Q: Which material will "float" higher on the mantle: 5 km thick oceanic crust or 40 km thick continental crust? Why?

Q: What is the difference between a graben and a half-graben?

Q: Explain the difference between "terrain" and "terrane."

Q: As mountains continue to rise in elevation, the processes of erosion and mass wasting are accelerated.

Q: Accreted terranes that are adjacent to each other will generally have similar geologic histories until the point where they accrete. After that, their geologic histories will differ.

Q: Because the Indian subcontinent is still colliding with the Eurasian Plate, the Himalayas are still actively forming.