44 terms

EAR 106 Exam 2

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Which of the following are effective ways of reducing the effects of flooding?
a. all (b. artificial levees; c. channelization; d. erosion controls; e. wetlands restoration)
Which of the following tectonic settings is the most likely to generate an explosive volcanic eruption?
subduction zone
Which of the following terms is used to describe a large circular depression that forms after an eruption when a magma chamber becomes empty and collapses in on itself?
caldera
Imagine a section of highway with a large outcrop of fractured rock that poses a serious rockfall hazard. Which of the following engineering controls would be the best choice for minimizing the chance of large rocks falling onto the roadway?
building a retaining wall
Which of the following is a common triggering mechanism that causes slopes to fail suddenly?
all (b. earthquakes; c. heavy rainfall events; d. wildfires; e. over-steepening a slope)
Which of the following human activities commonly causes the over-steepening of slopes, which then leads to mass wasting?
construction of roads
The viscosity of this magma would decrease if the temperature was ___ and/or its SiO2 content was ___
higher; lower
If the viscosity of this magma decreased, it would become ___ fluid-like, which means it would travel a ___ distance
more; greater
There are two basic types of volcanoes, shield and composite cone. Which of the following best describes composite cone volcanoes?
relatively small, erupt andesitic magma, and are highly explosive
Which of the following engineering controls would be best suited to strengthen a slope that has been over-steepened by cutting into the hillside during highway construction?
build a retaining wall
The nature of volcanic eruptions is closely related to plate tectonics and magma type. Which of the following best describes basaltic magma?
relatively SiO2 poor and hot
Which of the following volcanoes in the U.S. is most notably for having a history of massive mudflows, which today threatens large numbers of people?
Mt. Rainier, Washington
Which of the following best explains why excessive amounts of water can destabilize a slope?
increases internal pore pressure
Which of the following is not part of the hydrologic cycle?
sequestration
Streams located near the mouth of a river are quite different compared to those near the headwaters. What best characterizes streams near the mouth?
low velocity, high discharge, and meandering channels
Which of the following factors determine whether a volcanic eruption will be explosive or non-explosive?
magma viscosity and gas content
What best describes a pyroclastic flow?
dry avalanche of hot material
Stability of earth materials on slopes depends on the balance of gravitational and frictional forces. Which of the following does not have a measurable effect on the balance between gravity and friction?
atmosphere air pressure
Which of the following natural factors affect the degree or severity of flooding?
rainfall volume and infiltration capacity of the ground
As shown here, artificial levees provide protection against flooding, but make flooding worse upstream because ___
parts of the floodplain are no longer able store floodwaters
Artificial levees also encourage development within floodplains, which ___
leads to greater damages when levees fail
What best describes why volcanic mudflows are so dangerous to humans?
they move down stream valleys where people tend to live
Which of the following best explains why some volcanoes erupt so violently?
rapid decompression of dissolved gases
What best explains why groundwater baseflow is important to maintaining a healthy stream ecosystem in humid climates?
provides streams with a steady flow of water during dry periods
Which of the following is least likely to be associated with explosive volcanic eruptions?
lava flows
Which of the following is not a common problem associated with volcanic ash-fall?
forest fires
The use of engineering controls is one of the two basic methods for minimizing mass wasting hazards. Which of the following is the other basic approach to minimize mass wasting hazards?
avoid building in hazard zones
Viscosity is the measure of a fluid's resistance to a flow. Which of the following factors affect the viscosity of magmas?
temperature and SiO2 content
Suppose that engineers are unable to keep earth materials from coming down onto a highway. In this case, which of the following would be the most economical and effective technique for reducing the hazard?
build a protective structure
Which of the following best explains why urbanization has led to larger and more frequent floods?
large areas of land are covered with impermeable surfaces
What best describes a drainage basin?
land area that collects water for a given network of streams
Volcanic ash is composed of ___ which makes ash very ___
rock & glass fragments; abrasive
Because volcanic ash is composed of rocky material, it is also relatively ___
dense
In addition to causing buildings to collapse and failure of mechanical and electrical equipment, volcanic ash can mix with heavy rains to form dangerous ___
mudflows
Excessive ash can also lead to ___ in streams, which in turn can cause ___
sediment pollution; increased flooding
Volcanic ash forms when rock particles and lava droplets are ejected skyward
true
Rain or melting snow will infiltrate and eventually cause subsurface voids between fractures and sedimentary grains to become ___
saturated
The weight of this additional water causes the ___ pressure within the voids to increase, which reduces the friction between the solids
pore (fluid)
Downslope movement occurs when the ___ becomes less than the ___ in the slope direction
frictional forces; gravitational force
How do hydrologists measure the severity of floods?
height (stage) above which a stream overflows its banks
What best describes the basic role of streams in the Earth system?
drain water from the landscape and transport sediment
As the slope increases, the component of gravity in the slope direction (Gs) operating on a rock will ___
increase
The rock will begin to move only if the gravity component in the slope direction becomes greater than ___
the frictional resistance
Earthquakes, heavy rains, and removal of vegetation are considered ___ because they can ___ and cause earth materials to begin moving downslope
triggering mechanisms; upset the balance of forces