首页
登录
职称英语
MASS WASTING PROCESSES1 The downslope movement of rock, mud
MASS WASTING PROCESSES1 The downslope movement of rock, mud
游客
2025-02-08
10
管理
问题
MASS WASTING PROCESSES
1 The downslope movement of rock, mud, or other material under the influence of gravity is known as mass wasting. While the angle of the slope is a major factor in the potential for mass wasting, the slope is not the sole determiner of mass wasting events. Water plays a significant role, especially where it is plentiful during the rainy season. Earthquakes may cause rockslides, mudflows, and other mass movements. Factors such as the presence or absence of vegetation and human activities can also influence the potential for mass wasting.
2 One way to classify mass wasting processes is on the basis of the material involved, such as rock, debris, earth, or mud. The manner in which the material moves is also important and is generally described as a fall, a slide, or a flow. A fall occurs when weathering loosens boulders from cliffs or rock faces, causing the boulders to break away and fall. A slide takes place whenever material remains fairly coherent and moves along a well-defined surface. A flow involves the movement of debris containing a large amount of water.
3 Many mass wasting processes are described as slides. Rockslides occur when a coherent mass of rock breaks loose and slides down a slope as a unit. If the material involved is mostly separate pieces, it is called a debris slide. Slides are among the fastest and most destructive mass movements. Usually rockslides occur in a geologic setting where the rock layers are inclined, or where there are joints and fractures in the rock that are parallel to the slope. When such a rock unit is undercut at the base of the slope, it loses support and the rock eventually collapses. Rain or snowmelt can
trigger
a rockslide by wetting the underlying surface to the point that friction can no longer hold the rock in place. The fastest type of slide is a rock avalanche, in which a mass of rock literally floats on air as it moves downslope. The high speed of a rock avalanche is the result of air becoming trapped and compressed beneath the falling mass of debris, allowing it to move down the slope as a
buoyant
sheet.
4 Mudflows are relatively rapid mass wasting events that involve soil and a large amount of water. Because of their fluid properties, mudflows follow canyons and stream channels. Mudflows often take place in semiarid mountainous regions and on the slopes of some volcanoes. Although rainstorms in semiarid regions are infrequent, they are typically heavy when they occur. When a rainstorm or rapidly melting snow creates a sudden flood, large quantities of soil and loose rock are washed into nearby stream channels because there is usually little or no vegetation to
anchor
the surface material. The result is a flowing mass of well-mixed mud, soil, rock, and water. The consistency of the mudflow may be similar to
that
of wet concrete, or it may be a soupy mixture not much thicker than muddy water. The water content influences the rate of flow across the surface. When a mudflow is dense, it moves more slowly, but it can easily carry or push large boulders, trees, and even houses along with it.
5 In dry mountainous areas such as southern California, mudflows are a serious hazard to development on and near canyon hillsides.
The removal of native vegetation by brush fires has increased the probability of these destructive events.
Past mudflows have contributed to the buildup of fan-shaped deposits at canyon mouths. Such fans are relatively easy to build on and often have scenic views, so many have become desirable sites for residential development. However, because mudflows occur infrequently, homeowners are often unaware of the potential danger of building on the site of a previous mudflow.
6 Highly fluid, fast-flowing mudflows incorporate fine-grained sediment and are common after volcanic eruptions that produce large volumes of volcanic ash. Mudflows containing volcanic debris are called lahars, a word originating in Indonesia, a region that experiences many volcanic eruptions. Lahars occur when highly unstable layers of ash and debris become saturated with water and flow down steep volcanic slopes along stream channels. In the northwestern United States, the eruption of Mount St. Helens in 1980 created several lahars that
raced
down the valley of the Toutle River, altering the landscape in a relatively short period. [br] Which sentence below best expresses the essential information in the highlighted sentence in paragraph 5? Incorrect choices change the meaning in important ways or leave out essential information.
选项
A、Fire has destroyed much of the original vegetation, so mudflows are now more likely.
B、More damage to vegetation is caused by brush fires than by any other natural event.
C、It is necessary to remove dead and damaged vegetation after a mudflow but not after a fire.
D、Fires occur frequently in areas where the vegetation has been cleared for development.
答案
A
解析
The removal of native vegetation by brush fires... is paraphrased in Fire has destroyed much of the original vegetation... ; ... has increased the probability of these destructive events is paraphrased in ...so mudflows are now more likely. (1.7)
转载请注明原文地址:https://tihaiku.com/zcyy/3948273.html
相关试题推荐
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
MASSWASTINGPROCESSES1Thedownslopemovementofrock,mud
DADAANDPOPART1Dadawasasubversivemovementinthearts
DADAANDPOPART1Dadawasasubversivemovementinthearts
DADAANDPOPART1Dadawasasubversivemovementinthearts
DADAANDPOPART1Dadawasasubversivemovementinthearts
随机试题
In1994,theCarnegieCorporationreleasedareportto______.[br]Whatisthea
GregWoodburn,asophomoreattheUniversityofSouthernCalifornia,spends
同一个油罐组内油罐总容量,固定顶油罐组及固定顶油罐和浮顶、内浮顶油罐的混合罐组不
关于糖尿病的诊断下列哪项正确A.三多一少是诊断糖尿病必须具备的条件 B.所有病
学龄期保健中提到要注意预防传染病,并对传染病做到A、早发现 B、早报告 C、
如图所示,△ABC是底角为30°的等腰三角形,其内的矩形DEFG是由两个边长为1
下列关于劳务派遣的劳动合同,表述错误的是()。A.劳动合同中应当载明用工单
一组数据为“100~600”“600~1100”“1100~1600”“1600
乙公司是一家上市公司,适用的企业所得税税率为25%,当年息税前利润为900万元,
银行承兑汇票的承兑银行,应当按照票面金额向出票人收取()的手续费。A:千分之一
最新回复
(
0
)