Active Vocabulary

abruptly adv внезапно, резко

accept v признавать

apply v использовать, применять, употреблять

arid a сухой, безводный, засушливый

belt n пояс, зона, район, полоса

body (of water) масса воды, водная поверхность

clay n глина, глинозем

coarse a (sand) крупный (грубый) песок

consequence n следствие, последствие, результат

deposit v отлагать, наносить, намывать; отлагаться, осаждаться

desert n пустыня

devise v изобретать, разрабатывать

discredit v подвергать сомнению, ставить под сомнение

elevation n поднятие, повышение; высота (над уровнем моря); возвышение, возвышенность, высота, пригорок

emerge v появляться, показываться, возникать

fertile a плодородный

float v плавать, плыть

igneous a изверженный, вулканический

involve v включать в себя , содержать, предполагать, подразумевать, влечь за собой, вызывать (последствия), приводить к чему-либо, вовлекать, окутывать, покрывать, обволакивать.

isthmus n перешеек

lack v испытывать недостаток; недоставать, не хватать, быть недостаточным

limestone n известняк

outline n контур, очертание

peninsular n полуостров

predict v предсказывать

respond v отвечать, реагировать

ridge n горный хребет, гряда гор

shell n оболочка; земная кора, геологический твердый прослоек

smooth a гладкий, ровный

steep a крутой

stress n давление, напряжение

~ of weather непогода, буря

under the ~of под влиянием , под воздействием

stretch v тянуться, простираться

trace n след, отпечаток ; pl. - остатки

wear down v выветривать(ся), подвергать эрозии

weathing n выветривание, эрозия

uplift n подъем, геологический взброс

v подымать

Additional Reading Erosion

All the processes by which rocks are worn down and by which the debris is carried away are included in the general term erosion. The underlying cause of erosion is gravity. Such agents of erosion as running water and glaciers derive their destructive abilities from gravity, and gravity is responsible for the transport of removed material to lower and lower elevations. The leveling of landscape by erosion is often referred to as gradation.

Weathering

We have all seen the rough, pitted surfaces of old stone monuments and buildings and the progressive obliteration of their markings. This sort of disintegration, brought about by rainwater and atmospheric gases, is called weathering.

Weathering is in part a chemical process, in part a mechanical process. It participates in an important way by preparing rock material for easy removal by the more active erosional agents. Among the agents whose work is most obvious are streams, glaciers, wind, and waves. Less apparent is the erosional work of groundwater, water in crevices and channels beneath the surface. All these agents are capable of cutting slowly into solid, unweathered rock, but their work is greatly speeded by the disintegration of rocks into the softer material of the weathered layer.

Some of the minerals in igneous and metamorphic rocks are especially susceptible to chemical weathering, since they were formed under conditions very different from those at the earth’s surface and minerals stable under the former conditions are not necessarily stable under the latter. Most sedimentary rocks, on the other hand, consist of rock debris that has already undergone chemical weathering, and so are relatively resistant to further attack; the chief exception is limestone.

Ferromagnesian minerals are readily attacked by atmospheric oxygen with the help of carbonic acid (formed by the solution of carbon dioxide in water) and of organic acids from decaying vegetation. Their iron content changes to rustlike compounds whose red and brown colors are familiar as stains on the surface of rocks containing these minerals. Feldspars and other silicates containing aluminum are in large part altered to clay minerals. Among common sedimentary rocks limestone is most readily attacked by chemical weathering because of the solubility of calcite in carbonic acid. Exposures of this rock can often be identified simply from the pitted surfaces and enlarged cracks that solution produces. Quartz and white mica are extremely resistant to chemical attack and usually remain as lose grains when the rest of a rock is thoroughly decayed. Rocks consisting wholly of silica, like chert and most quartzites, are practically immune to chemical weathering.

Mechanical weathering is often aided by chemical attack; not only is the structure of a rock weakened by the decomposition of its minerals, but fragments are actively wedged apart because the chemical changes in a mineral grain usually result in an increased volume. The most effective process of mechanical disintegration that does not involve chemical action is the freezing of water in crevices, since water expands when it turns into ice and considerable forces can be developed in this way. Just as water freezing in an automobile engine on a cold night may split the block, so water freezing in tiny cracks is an effective wedge for disrupting rocks. Plant roots aid in rock disintegration by growing and enlarging themselves in cracks.

Weathering processes clothe the naked rock of the earth’s crust with a layer of debris made up largely of clay mixed with rock and mineral fragments. The upper part of the weathered layer, in which rock debris is mixed with decaying vegetable matter, is the soil. From a human point of view the formation of soil is by all odds the most important result of weathering.