2.10流水的侵蚀和沉积
Section outline
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Lesson Objectives
::经验教训目标- Explain how flowing water causes erosion.
::解释水流如何导致侵蚀。
- Describe how runoff, streams, and rivers change Earth’s surface.
::描述径流、溪流和河流如何改变地球表面。
- Identify features caused by groundwater erosion.
::查明地下水侵蚀造成的特征。
Lesson Vocabulary
::词汇表课程- alluvial fan
::冲积冲积扇风扇
- cave
::洞洞洞
- delta
::三角三角
- deposition
::积存
- erosion
::侵蚀
- floodplain
::洪泛石
- levee
::列列列
- meander
::中 年 中
- oxbow lake
::湖
- saltation
::盐盐盐
- sinkhole
::坑洞
- suspension
::中止暂停
- traction
::牵引
Introduction
::导言Erosion causes changes to Earth's surface. Erosion is what causes pieces of rock and soil to move. These pieces of rock and soil are called sediment. There are several causes of erosion. These causes are flowing water, waves, wind, ice, and gravity.
::侵蚀导致地球表面的变化。侵蚀是导致岩石和土壤块块移动的原因。这些岩石和土壤块被称为沉积物。有几种侵蚀原因。这些原因包括水流、波浪、风、冰和重力。How Flowing Water Causes Erosion and Deposition
::侵蚀和沉积Flowing water causes sediment to move. Flowing water can erode both rocks and soil.
::流水导致沉积物移动,流水会侵蚀岩石和土壤。You have already learned that materials can dissolve in water. With enough time, even rocks can be dissolved by water. This process happens really slowly. It may take over a million years to dissolve a rock. It doesn't matter how big the rock is. With enough time, flowing water can dissolve it.
::您已经学会了材料可以在水中溶解。 足够长的时间, 甚至岩石也可以被水溶解。 这一过程会非常缓慢地发生。 溶解岩石可能需要一百万年的时间。 岩石的大小并不重要。 足够长的时间, 流水可以溶解它。Moving water also has the ability to move small pieces of rock and soil. How can water move a rock? Doesn't it need energy? Of course, water gets its energy because it is moving. Moving water has kinetic energy. Things that have more energy can do more work. When water stops moving it will have no energy. It will no longer be able to move the rock and soil. When this happens the rock and soil will settle to the bottom of the calm water. Scientists call this process deposition.
::移动水也有能力移动小块岩石和土壤。 水如何移动岩石? 当然, 水需要能量吗? 当然, 水因其移动而获得能量。 移动水有动能。 具有更多能量的东西可以做更多的工作。 当水停止移动时, 它将失去能量。 它将不再能够移动岩石和土壤。 当发生这种情况时, 岩石和土壤将沉入平静水底。 科学家称此过程为沉积 。Water Speed and Erosion
::水速和侵蚀Faster-moving water has more kinetic energy. Therefore, it can carry larger particles. It can also carry more particles. What causes water to move faster? The steeper the slope, the faster the water flows. It's just like a toy car rolling down a ramp. It will roll the fastest when the ramp is steep. It will roll slower when the ramp is less steep. If the ramp is flat, it may have no motion. The slope of the land causes water to move faster. If a stream or a river is flowing down a mountain, it will move more quickly. If it is flowing across a flat area, it will move slowly.
::快速移动的水具有更多的动能。 因此, 它可以携带更大的粒子, 也可以携带更多的粒子。 是什么导致水移动更快? 如何使水移动更快? 斜坡越陡越高, 水流越快。 它就像玩具车一样向斜坡滚动。 当斜坡倾斜时, 它会滚动得最快。 当斜坡不那么陡坡时, 它会滚动得越慢。 如果斜坡平坦, 它可能没有运动。 陆地的斜坡会让水移动得更快。 如果一条溪流或一条河流向山下, 它会移动得更快。 如果它横跨平坦地区, 它会慢慢移动 。Particle Size and Erosion
::粒子大小和侵蚀The size of particles determines how they are carried by flowing water. This is illustrated in Figure .
::粒子的大小决定着它们是如何通过流水携带的。图6说明了这一点。How Flowing Water Moves Particles. How particles are moved by flowing water depends on their size.
::流水如何移动粒子。 流水如何移动粒子取决于其大小。Some minerals dissolve in water. The minerals are then carried along in the solution. Small particles, such as clay and silt, are carried in suspension . They are mixed throughout the water. These particles are not dissolved in the water. Somewhat bigger particles bounce along the bottom. Particles, such as sand, move in little jumps near the stream bottom. They are nudged along by moving water. The biggest particles move in a different way. They are too big to hop. Instead, they roll along the bottom. Gravel and pebbles move in this way. These particles roll or drag along the bottom of the water.
::一些矿物质溶于水中,矿物质在溶液中随附。小粒子,如粘土和淤泥,在悬浮中携带,在水中混合。这些粒子不会溶于水中。有些更大的粒子在水底反弹。一些粒子,如沙粒,在水底上小跳动。它们通过移动水而拉动。最大的粒子以不同的方式移动。它们太大而不能跳动。相反,它们沿着底部滚动。碎石和碎石以这种方式移动。这些粒子在水底滚动或拖动。Deposition by Water
::水沉积Flowing water slows down when it reaches flatter land. Maybe it flows into a small lake or pond. What do you think happens then? The water starts dropping the particles it was carrying. As the water slows, it drops the largest particles first. The smallest particles settle last.
::当流水到达平坦的陆地时,流水会减慢速度。 也许流到一个小湖或池塘里。 你认为会发生什么呢? 水开始滴下它携带的粒子。 当水减慢时,它会先掉下最大的粒子。 最小的粒子会最后落下 。Erosion and Deposition by Surface Water
::地表水侵蚀和沉积Water that flows over Earth’s surface includes runoff, streams, and rivers. All these types of flowing water can cause erosion and deposition.
::流过地球表面的水包括径流、溪流和河流。 所有这些类型的流水都会导致侵蚀和沉降。Erosion by Runoff
::径流侵蚀Sometimes it rains a lot at one time. It rains so hard that the rain cannot soak into the ground. Instead, it runs over the land. Gravity causes the water to flow downhill. As the runoff flows, it may pick up loose material. These materials may include bits of soil and sand. It is carried off by this running water across the surface of the land.
::有时它经常下大雨,下大雨,雨量很大,雨量无法渗入地面,相反,它横跨陆地,重水使水流下山,随着径流流,它可能收集出松散的物质,其中可能包括土壤和沙子,它被这种自来水冲过陆地表面。Runoff is likely to cause more erosion if the land is bare. Plants help hold the soil in place. The runoff water in Figure is brown. It has turned brown because it eroded soil. It leaves behind only bare soil. Does erosion happen around where you live? Can you find evidence of erosion? What should you look for?
::如果土地是空的, 径流可能会造成更多的侵蚀。 植物有助于将土壤固定在原地。 图中的径流水是棕色的。 图中的径流水是褐色的。 它因侵蚀土壤而变成棕色的。 它只留下赤裸的土壤。 侵蚀是否发生在你居住的地方? 你能找到侵蚀的证据吗? 你们要寻找什么?Erosion by Runoff. Runoff has eroded small channels through this bare field.
::径流侵蚀 径流侵蚀了小通道Much of the material eroded by runoff makes its way into a body of water. These bodies of water include streams, rivers, ponds, lakes, or oceans. Runoff is an important cause of erosion. That’s because it occurs over so much of Earth’s surface. Farmland is especially under danger from this type of erosion. Farmers can lose much of their topsoil. They take great care to prevent soil erosion. Without topsoil, crops cannot grow.
::这些水体包括溪流、河流、池塘、湖泊或海洋。 径流是侵蚀的重要原因。 这是因为径流发生在地球表面的很多地方。 农田尤其面临着这种侵蚀的危险。 农民可以失去大部分表土。 他们非常小心地防止土壤侵蚀。 没有表土,作物就无法生长。Erosion by Mountain Streams
::山流侵蚀Streams often start high in the mountains. Their slopes of mountains are very steep. As a result, the streams flow very quickly. You can see an example in Figure . The quick speed of the water causes a lot of erosion. The fast moving water carves deep into the rock and soil it flows over. Mountains streams cut narrow V-shaped channels.
::河流通常从山上开始高起,山坡非常陡峭。结果,溪流流动非常迅速。您可以看到图中的例子。水的快速速度导致大量侵蚀。快速移动的水在岩石和土壤深处倾斜。山溪切断了狭窄的V形通道。Mountain Stream. This mountain stream races down a steep slope.
::山流 这山流沿着斜坡冲下How a Waterfall Forms
::瀑布形式如何Have you ever seen a waterfall? Perhaps you have seen a picture of one? Waterfalls may be formed by mountain streams. They typically form where water is moving quickly. As shown in Figure , waterfalls need special conditions to form. They form where the stream flows from an area of harder onto an area of softer rock. The water erodes the softer rock faster than the harder rock. This causes a step-like feature to form. This process is what creates a waterfall. As erosion continues, the waterfall slowly moves upstream.
::你曾见过瀑布吗?你曾见过瀑布吗?瀑布可能由山流形成。瀑布通常形成于水流迅速移动的地方。如图所示,瀑布需要特殊条件才能形成。它们形成于溪流从较硬地区流到较软岩石地区的地方。水侵蚀较软岩石的速度快于较硬岩石地区。这造成一个类似步态的特征形成。这是形成瀑布的过程。随着侵蚀的继续,瀑布慢慢向上游移动。How a Waterfall Forms and Moves. Why does a waterfall keep moving upstream?
::为什么瀑布一直往上游移动?Erosion by Slow-Flowing Rivers
::慢流河侵蚀Rivers flowing over gentle slopes move more slowly. They move much more slowly than a mountain stream. These slow moving streams create different types of features than mountain streams. Slow moving water erodes the sides of their channels more than the bottom. Also, large curves in the stream form. These curves are called meanders . Meanders are caused by erosion and deposition.
::流过温坡的河流移动较慢,移动速度比山流慢得多。这些缓慢的移动溪流创造了不同于山流的特征。 缓慢的移动水会侵蚀其河道的两侧而不是底部。 另外, 流状的曲线也很大。 这些曲线被称为“ 下游 ” 。 鼠标是侵蚀和沉积造成的。Remember, faster moving water causes erosion more quickly. Slower moving water erodes material more slowly. If water is moving slowly enough, the sediment being carried may settle out. This settling out, or dropping off, of sediment is deposition. The curves are called meanders because they slowly “wander” over the land. You can see how this happens in Figure .
::记住,更快的移动水会更快地造成侵蚀。更慢的移动水会更慢地侵蚀材料。如果水移动速度足够缓慢,沉积物会沉淀下来。沉淀物的沉淀或丢弃就是沉积。曲线被称为“弯曲”,因为它们在陆地上缓慢地“倾斜 ” 。您可以在图中看到这种情况是如何发生的。Meanders form because water erodes the outside of curves and deposits eroded material on the inside. Over time, the curves shift position.
::由于水侵蚀了曲线的外部,沉积侵蚀了内部物质,因此测算器形成。随着时间推移,曲线会移动位置。As meanders erode from side to side, they create a floodplain . This is a broad, flat area on both sides of a river. Eventually, a meander may become cut off from the rest of the river. This forms an oxbow lake , like the one in Figure .
::河岸两侧都是宽阔、平坦的地区。 最终, 草地可能与河的其余部分隔绝。 这形成一个牛弓湖, 和图中的一样。Deposition by Streams and Rivers
::溪流和河流沉积When a stream or river slows down, it starts dropping its sediments. Larger sediments are dropped in steep areas. Some smaller sediments can still be carried by a slow moving stream or river. Smaller sediments are dropped as the slope becomes less steep.
::当溪流或河流放慢速度时,它开始沉积沉降,较大的沉积在陡峭地区沉降,一些较小的沉积仍然可以由缓慢移动的溪流或河流承载,随着坡坡变低,较小的沉积会下降。Alluvial Fans
::冲积粉扇In arid regions, a mountain stream may flow onto flatter land. The stream comes to a stop rapidly. The deposits form an alluvial fan , like the one in Figure .
::在干旱地区,山河可能流到平坦的土地上。河水迅速停顿。矿床形成冲积层,就像图中的一样。An alluvial fan in Death Valley, California (left), Nile River Delta in Egypt (right).
::埃及尼罗河三角洲(右)。Deltas
::三角三角洲Deposition also occurs when a stream or river empties into a large body of still water. In this case, a delta forms. A delta is shaped like a triangle. It spreads out into the body of water. An example is shown in Figure .
::当溪流或河流渗入大片静水时,也会出现沉积。在这种情况下,形成三角洲。三角洲的形状像三角形。它会扩散到水体中。一个实例在图中显示。Deposition by Flood Waters
::洪水沉积A flood occurs when a river overflows its banks. This might happen because of heavy rains.
::当河水溢出河岸时,就会发生洪水,可能是因为暴雨。Floodplains
::洪泛In very flat regions, flood water may spread out on the surface of the land. It then slows down and drops its sediment. If a river floods often, a floodplain develops. A floodplain is an area where a thick layer of rich soil is left behind as the floodwater recedes. That’s why floodplains are usually good places for growing plants. They are very flat areas and they have very rich soils.
::在非常平坦的地区,洪水可能散布在陆地表面,然后放慢速度,沉降沉积。如果河流洪涝频繁发生,洪泛平原就会形成。 洪泛平原是洪水退缩时留下厚厚土壤层的地区。 这就是为什么洪泛平原通常是生长植物的好地方。 洪泛平坦的地区非常平坦,土壤也非常丰富。The Nile River valley is a great example of a floodplain. Each year, the Nile River rises over its banks. This floodwater carries a lot of sediment. This sediment has been eroded off areas of land from upstream. This sediment is dropped as the water slows down after spreading across the land. What is left behind is a very rich soil. That's why crops can be raised in the middle of a sandy desert.
::尼罗河河谷是洪泛地带的一个很好的例子。 尼罗河河河水位每年上升, 河岸上有许多沉积。 洪水水中有许多沉积物。 沉积物从上游的陆地被侵蚀。 这种沉积物随着水在陆地上蔓延而下降。 留下的是一个非常丰富的土壤。 这就是为什么作物可以在沙沙沙沙漠中生长。Natural Levees
::自然自然收入A flooding river often forms natural levees along its banks. A levee is a raised strip of sediments deposited close to the water’s edge. You can see how levees form in Figure .
::洪涝河往往形成沿河岸的天然堤流。 堤流是沉积在水边附近的高沉积层。 您可以在图中看到堤流是如何形成的。This diagram shows how a river builds natural levees along its banks.
::这个图显示了河水如何沿河岸建造天然堤坝。Erosion and Deposition by Groundwater
::地下水侵蚀和沉积Not all water travels on the surface. Some water travels underground. How does this happen? Some water soaks into the ground. It travels down through tiny holes in soil. It seeps through cracks in rock. The water moves slowly. It is pulled deeper and deeper into the ground by gravity. Underground water can also erode and deposit material.
::水不是全部在地表上流动,有些水在地下流动,怎么会这样呢?有些水渗入地表,有些水渗入地表,穿过土壤中的小洞,渗入岩石中的裂缝,水缓慢移动,水因重力而更深、更深地钻入地表,地下水也可以侵蚀和沉积材料。Caves
::洞洞洞洞洞As water flows through, it causes changes. The flowing water dissolves some types of rock. Some rocks dissolve more easily than others. Over time, the water may dissolve large areas of rocks. With enough time, holes, or caves, can form. Groundwater drips from the ceiling to the floor of a cave. Even deep in the ground, water is still pulled by gravity. This falling water is rich in dissolved minerals. Some of these minerals do not stay dissolved. When this happens, the minerals start to build up. They build up on the ceiling of the cave to create formations called stalactites. A stalactite is a pointed, icicle-like mineral. They form on the ceiling of a cave. They drip to the floor of the cave. It is there the minerals in the water harden to form stalagmites. A stalagmite is a more rounded mineral deposit. It forms on the floor of a cave ( Figure ). Both types of formations grow in size as water keeps dripping and more minerals are deposited.
::随着水流的流过,水会改变。流水会溶解一些类型的岩石。有些岩石会比其他岩石更容易溶解。随着时间的流逝,水会溶解大片岩石。随着时间、洞洞或洞穴的形成,地下水会从天花板滴到洞穴的地板上。即使深地,水也会被引力所拉动。这种沉降的水是丰富的溶解矿物质。有些矿物质不会继续溶解。一旦发生这种情况,矿物质就会开始积聚。在洞穴的顶层上堆积,以形成一种叫作石化物的构造。一种石化石化石是尖尖的,类似于冰球的矿物质。它们形成在洞穴的顶上,它们滴到洞穴的地板上,是坚硬的矿物质,形成炉渣石。一个更圆的矿藏在洞穴里(Figre)形成一种矿物质。两种矿物质随着水不断滴水和更多的矿物质沉积在洞底上生长。This cave has both stalactites and stalagmites.
::这个洞穴既有石化物 也有stalagmites。Sinkholes
::汇孔As erosion by groundwater continues, the ceiling of a cave may collapse. The rock and soil above it sink into the ground. This forms a sinkhole on the surface. You can see an example of a sinkhole in Figure . Some sinkholes are big enough to swallow vehicles and buildings. Florida has a lot of sinkholes. Look at a map of Florida and notice the numerous round lakes. These lake are sinkholes that have filled with water.
::随着地下水侵蚀的继续,洞穴的天花板可能会塌陷,洞穴上面的岩石和土壤会沉入地底。这在地表形成一个坑洞。你可以在图中看到一个坑洞的例子。有些坑洞的大小足以吞噬车辆和建筑物。佛罗里达州有许多坑洞。看看佛罗里达州的地图,并注意许多圆湖。这些湖是充满水的坑洞。A sinkhole.
::一个坑洞。Lesson Summary
::经验教训摘要- Water flowing over Earth’s surface or underground causes erosion and deposition.
::地球表面或地下的水流造成侵蚀和沉降。
- Water flowing over a steeper slope moves faster and causes more erosion.
::水流过一个更陡峭的斜坡,移动速度更快,并造成更多的侵蚀。
- How water transports particles depends on their size. When water slows down, it starts depositing sediment. This process starts with the largest particles first.
::水转移粒子如何取决于其大小。 当水减慢时, 它开始沉积沉积。 这个过程首先从最大的粒子开始 。
- Runoff erodes the land after a heavy rain. It picks up sediment. Runoff carries most of the sediment to bodies of water. Mountain streams erode narrow, V-shaped valleys and waterfalls.
::径流在大雨后侵蚀土地,吸收沉积物,径流将大部分沉积物带入水体,山流侵蚀狭窄的V形山谷和瀑布。
- Erosion and deposition by slow-flowing rivers create broad floodplains and meanders.
::缓慢流出河流的侵蚀和沉积造成了大面积的洪泛和下沉。
- Deposition by streams and rivers may form alluvial fans and deltas. Floodwaters may deposit natural levees.
::溪流和河流的沉积可能形成冲积扇和三角洲,洪水可能沉积自然漂流。
- Erosion and deposition by groundwater can form caves and sinkholes. Stalactites and stalagmites are mineral deposits. They build up in caves as water continues to drip.
::地下水的侵蚀和沉积可形成洞穴和汇洞,腐蚀物和渣子是矿藏,随着水的继续滴落,在洞穴中积聚。
Lesson Review Questions
::经验回顾问题Recall
::回顾- Define erosion.
::界定侵蚀。
- What is deposition?
::证词是什么?
- When does flowing water deposit the sediment it is carrying?
::流水何时会沉积沉积物?
- What happens to the sediment eroded by runoff?
::径流侵蚀的沉积物会怎样?
- Describe how a waterfall forms.
::描述瀑布是如何形成的
- What are meanders?
::什么是卑鄙小人?
Apply Concepts
::应用概念- Make a table that relates particle size to the way particles are transported by flowing water.
::制作一个将粒子大小与粒子通过流水输送的方式相联系的表格。
- Create a sketch that shows effects of groundwater erosion and deposition.
::绘制一张显示地下水侵蚀和沉积影响的草图。
Think Critically
::仔细仔细思考- Explain why mountain streams erode V-shaped valleys.
::解释为什么山溪侵蚀V形山谷。
- What might be pros and cons of living on the floodplain of a river?
::生活在河流的洪泛平原上有什么利弊?
Points to Consider
::需要考虑的要点Ocean waves are another form of moving water. They also cause erosion and deposition.
::海洋波浪是移动水的另一种形式,还造成侵蚀和沉降。- How do waves erode shorelines?
::海浪如何侵蚀海岸线?
- What landforms are deposited by waves?
::海浪所沉积的地表是什么?
- Explain how flowing water causes erosion.
