52 Landslides-Low

Landslides FOCUS Question How do landslides change Earth's surface?

滑坡焦点问题滑坡如何改变地球表面?

Moving Earth It's a rainy day in the mountains. The forest is quiet, except for the peaceful sound of raindrops. Suddenly, there is a long, loud roar as the surface on one side of a hill breaks off and slides away. The soil tears apart, churning like a washing machine, while trees and rocks are swept away. The wall of debris finally comes to a stop on the flat ground below, burying a road. This event is called a landslide. Landslides are natural disasters in which large masses of rock, mud, or soil suddenly collapse and move downhill. Landslides can quickly change the landscape.

这是山里的一个雨天。 森林里静悄悄的，只有淅沥的雨点声。 突然，传来一声长而响亮的轰鸣声，一座山的一侧表面断裂并滑落。 土壤撕裂，像洗衣机一样翻腾，树木和岩石被冲走。 碎石墙最终在平地上停了下来，埋下了一条路。 这种事件被称为山体滑坡。 山体滑坡是一种自然灾害，大量的岩石、泥浆或土壤突然坍塌并向山下移动。 山体滑坡可以迅速改变地貌。

Slow Versus Quick The shape of land changes all the time. Through the processes of weathering and erosion, water and wind wear away Earth's surface. Sometimes flowing water and blowing wind move rocks and soil a bit at a time. Gravity can move rocks and soil downhill over centuries. Eventually, mountains wear down, rivers carve valleys, and plains grow smooth and flat. However, landslides happen quickly. When a slope is very steep or the land becomes too loose or fragile, large masses of rock and soil can give way and fall all at once. There are three main types of landslides flows, slides and falls.

慢与快陆地的形状一直在变化。 通过风化和侵蚀的过程，水和风侵蚀着地球表面。 有时流动的水和吹的风一次移动一点岩石和土壤。 几个世纪以来，重力可以把岩石和土壤往下移。 最终，山脉磨损，河流雕刻山谷，平原变得光滑平坦。 然而，山体滑坡很快就会发生。 当一个斜坡非常陡峭，或者土地变得过于松散或脆弱时，大量的岩石和土壤可能会坍塌并同时倒塌。 滑坡主要有三种类型:流、滑和落。

Flows A flow happens when land acts more like a liquid than a solid. It oozes or rushes downhill, tumbling as it goes. It buries the land below like a flood. A flow can be strong enough to break off trees and pick up large rocks. Flows almost always happen in soil made of small particles and usually take place when the soil is very wet. When soil becomes mud, a mudflow may form. The land easily flows away. A mudflow often occurs during periods of heavy rainfall. But small, loose bits of soil like sand or gravel can also flow when they are dry. This is a rockflow.

当土地更像液体而不是固体时，就会发生流动。 它渗出或冲下山坡，一边走一边翻滚。 它像洪水一样淹没了下面的土地。 水流强大到足以折断树木，卷起大石头。 流动几乎总是发生在由小颗粒组成的土壤中，通常发生在土壤非常潮湿的时候。 当土壤变成泥浆时，就可能形成泥石流。 土地很容易流失。 泥石流常发生在强降雨期间。 但小而松散的土壤，如沙子或砾石，在干燥时也会流动。 这是岩流。

Slides and Falls A slide happens when an entire slab of land breaks off and rushes downhill. Usually there is a layer of soft or loose rock underground. The weak layer can't support the ground above it, so the top layer gives way. Slides happen more often where water seeps into the rock and weakens it. A fall happens when a chunk of rock breaks off all at once. These sudden crashes happen on very steep land, like cliffs, or places where the ground is hollow beneath the rock. Science in Your World The Old Man of the Mountain was a popular cliff in New Hampshire that looked like a human face. In 2003, the rocks of the "face" broke off and fell into the valley below.

滑坡发生在整块土地断裂并冲下山坡的时候。 通常地下有一层柔软或疏松的岩石。 薄弱的一层无法支撑上面的地面，所以最上面的一层就垮了。 当水渗入岩石并使其变弱时，滑坡更常发生。 当一块岩石突然断裂时，就会发生坠落。 这些突然的撞击发生在非常陡峭的土地上，比如悬崖，或者岩石下面的地面是中空的地方。 山中的老人是新罕布什尔州一个很受欢迎的悬崖，看起来像一张人脸。 2003年，“面”的岩石断裂，落入下面的山谷。

What Causes Landslides? All landslides ultimately occur for the same reason— gravity. Landslides happen on sloped land, such as mountains, hills, canyons, and cliffs. What makes some slopes suddenly give way while others remain intact? Water Water is the main cause of landslides. When it rains or snows more than normal, landslides are more likely to occur. Heavy rain or flooding can turn soil into slick mud, and rocks become slippery— both of which cause flows. Gradual water erosion can also lead to a landslide. Waves create steep sea cliffs, and rivers carve out canyons. If a slope gets too steep, the land can suddenly give way. Water can also trickle into cracks in rock over time. When the water freezes, it expands, breaking the rock apart and sending it tumbling.

山体滑坡的原因是什么?所有的滑坡最终都是由同一个原因引起的——重力。 山体滑坡发生在倾斜的土地上，如山脉、丘陵、峡谷和悬崖。 是什么让一些斜坡突然倒塌，而另一些却完好无损? 水是滑坡的主要原因。 当雨雪超过正常时，山体滑坡就更容易发生。 大雨或洪水会使土壤变成滑溜溜的泥浆，岩石变得很滑，这两者都会导致洪水。 逐渐的水侵蚀也会导致滑坡。 海浪制造了陡峭的海崖，河流雕刻出峡谷。 如果坡度太陡，土地就会突然坍塌。 随着时间的推移，水也会渗入岩石的裂缝。 当水结冰时，它会膨胀，把岩石打碎并使其翻滚。