地理,關於landslide,用英文答(20點)!!!!

What is a landslide?
-the movement of soil and rock down a slope die to gravity

What are the impacts of landslides on people?
-injury or death of people
-collapse of buildings,people affected become homeless
-blocking of roads,traffic congestion
-damage to vegetation

What are the causes of landslides?
-Heavy or prolonged rain washes loose rock and soil down slope
-Hilly relief and steep slopes
-Urban development e.g. house and roads on steep slopes

How to prevent landslides?
-Check and repair slopes regularly
-check and clear drainage channels before and after heavy rainstorms
-spread cement on slopes
-build retaining wall
-remove large unstable rocks
-plant trees on slopes
-provide early warnings of landslides to the public

What is a landslide?
-the movement of soil and rock down a slope die to gravity

What are the impacts of landslides on people?
-injury or death of people
-collapse of buildings,people affected become homeless
-blocking of roads,traffic congestion
-damage to vegetation

What are the causes of landslides?
-Heavy or prolonged rain washes loose rock and soil down slope
-Hilly relief and steep slopes
-Urban development e.g. house and roads on steep slopes

How to prevent landslides?
-Check and repair slopes regularly
-check and clear drainage channels before and after heavy rainstorms
-spread cement on slopes
-build retaining wall
-remove large unstable rocks
-plant trees on slopes
-provide early warnings of landslides to the public

A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. Although gravity acting on an over steepened slope is the primary reason for a landslide, there are other contributing factors affecting the original slope stability:erosion by rivers, glaciers, or ocean waves create oversteepened slopes rock and soil slopes are weakened through saturation by snowmelt or heavy rains earthquakes create stresses that make weak slopes fail (see liquefaction, Hope Slide) volcanic eruptions produce loose ash deposits, heavy rain, and debris flows. vibrations from machinery, traffic, blasting and even thunder may trigger failure of weak slopes excess weight from accumulation of rain or snow, stockpiling of rock or ore, from waste piles, or from man-made structures may stress weak slopes to failure and other structures groundwater pressure acting to destabilise the slope in shallow soils, the removal of deep-rooted vegetation that binds the colluvium to bedrock.
Elements at risk
1. Settlements built on steep slopes.
2. Buildings at the mouth of the streams emerging from the mountain valley.
3. Buildings constructed without appropriate foundation for a given soil and in slopy areas are also at risk.
4. Roads, communication line and buried utilities are vulnerable.
Special types of landslides
Debris flow
Slope material that becomes saturated with water may develop into a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses, and cars, thus blocking bridges and tributaries causing flooding along its path.
Muddy-debris flows in the Alpine areas cause severe damage to structures and infrastructure and often claim human lives. Muddy-debris flows can start as a result of slope-related factors, and shallow landslides can dam stream beds, provoking temporary water blockage. As the impoundments fail, a "domino effect" may be created, with a remarkable growth in the volume of the flowing mass, which takes up the debris in the stream channel. The solid-liquid mixture can reach densities of up to 1.8-2 tons/m³ and velocities of up to 13-14 ms-1 (Chiarle and Luino, 1998; Arattano, 2003). These processes normally cause the first severe road interruptions, due not only to deposits accumulated on the road (from several cubic metres to hundreds of cubic metres), but in some cases to the complete removal of bridges or roadways or railways crossing the stream channel. Damage usually derive from a common underestimation of mud-debris flows: in the alpine valleys, for example, bridges are frequently destroyed by the impact force of the flow because their span is usually calculated only for a water discharge. For a small basin in the Italian Alps (area = 1.76 km²) affected by a debris flow, Chiarle and Luino (1998) estimated a peak discharge of 750 m3/s for a section located in the middle stretch of the main channel. At the same cross section, the maximum foreseeable water discharge (by HEC-1), was 19 m³/s, a value about 40 times lower than that calculated for the debris flow that occurred.
Sturzstrom
A sturzstrom is a rare, poorly understood type of landslide. Often very large, these slides are unusually mobile, flowing very far over low angle, flat, or even slightly uphill terrain. They are suspected of "riding" on a blanket of pressurized air, thus reducing friction with the underlying surface.
See also: Slump
Related phenomena
An avalanche, similar in mechanism to a landslide, involves a large amount of ice, snow and rock falling quickly down the side of a mountain. Usually the snow builds in cornices or forms over a weaker layer of snow, increasing the danger of an avalanche.
A pyroclastic flow is caused by a collapsing cloud of hot ash, gas and rocks from a volcanic explosion that moves rapidly down an erupting volcano.