Lesson 9

Text A

What are land forms?

I. Read and memorize the following words:

abruptly– різко accumulate – накопичувати amount (n)– кількість apply – застосовувати bedrock – грунт залягання beneath – під, break (v,n)– ламатися, розколина break apart– розламуватись canyon – каньйон catch – схопити cause (v)– викликати characteristics – характеристика collide – стикатися, зіткнутися complex – складний crumble – кришити/cь/ crush (v)– роздавлювати deposit (v)– відкладати develop – розвиватись dome-shaped – у формі купола drain (v) – осушувати dry out – висихати dump(v)– скидати enormous – величезний erode– піддаватися ерозії erupt – вивергатись expose – виставляти fault – зсув find – знаходити flood (v)– затопити fold(v)– згинати, cкладати force (n)– сила glacier – льодовик gorge – вузька ущелина instead– замість

intrude – вторгатись landform – форма землі landscape – ландшафт layer(n,v)– шар, нашаровувати leave – залишати magma – магма major – більший, важливий,величезний make up (v) - складати, створити massive - масивний, великий occur– траплятись origin – походження plain – рівнина plate – плита plateau – плато pressure – тиск push up – виштовхувати вверх relative to – по відношенню до relatively– відносно remain – залишатись retreat (v)– відступати ridge– кряж, хребет rock (n)– порода sediment – осадочна порода shape (v)– формувати share – розділяти slab – плита slide (v)– ковзати stage (n)– етап surround – оточувати tableland – плоскогір‘я, плато uplift – підніматись valley – долина volcanic – вулканічний volcano– вулкан

II. Expressions for the text comprehension;

alluvial plain – алювіальна рівнина both... and – як..., так і closing vise– стискуючі лещата coastal plain– берегова рівнина complex process– складний процес compressing plates– стискуючі плити continental slope– континентальний схил crustal rock– порода кори depositional stage– стадія відкладення flat plain– плоска рівнина general category– загальна категорія geologic period– геологічний період glacial plain– льодова рівнина igneous соге– пірогенне ядро lake bed– озерне дно, русло lake plain– озерна рівнина land surface – земна поверхня lava plain– лавова рівнина layered rocks– зашаровані породи load of sediment – вага осадку

mountain building– горетворення mountain range– горний кряж mountain system – горна система moving plate – рухаюча плита ocean floor – океанське дно orogenic stage – орогенна стадія sea level– рівень моря sediment layer– осадочний шар sedimentary rock – осадочна порода stretches of land – земні простори subduction zone– зона оубдукції, подвигу surface of plains – поверхня рївнин surrounding landscape – оточуючий ландшафт tops of plateaus – верхівки плато upper mantle– верхня мантія upwarped mountains – скручєні догори гори widening ocean – розширюючий океан wonderfulvariety– надзвичайна різноманітність

What are land forms?

Earth's landscape has a wonderful variety. The features making up earth's surface are called landforms. Earth's landforms can be put into three general categories - mountains, plateaus and plains. A mountain is an area of earth's surface abruptly rising much higher than the surrounding landscape. Mountains can be found on the ocean floor as well as on earth's land surfaces. All mountains aге formed by the complex processes that continue to shape earth's crust. For example, the Appalachian mountains were formed when slabs of earth's crust and upper mantle collided with each other. The forces caused the rocks to crumble and fold to form many ridges and valleys. Sometimes so much pressure is applied to rocks that they break rather than fold. These breaks in rocks, along which movement occurs, are called faults. Rocks slide past each other along faults when force is applied. Fault-block mountains are formed when enormous blocks of rock move up or down relative to the surrounding bedrock. When massive amounts of crustal rocks are pushed up into domc-shaped features, upwarped mountains are formed. Upwarped mountains often have igneous cores.

Although some important mountain systems are fault-block or volcanic in origin many of the world's major mountain systems are fold mountains. These develop in two stages; the depositional stage and the orogenic stae. The first stage begins when a continent breaks apart, leaving a widening ocean between the parts. Over time, rivers dump their load of sediment into the ocean and sediment layers form on the continental slope. The depositional stage might continue for a whole geologic period of time, as huge amounts of sediment accumulate. At some point a subduction zone may develop (one plate moves under another or a moving plate changes direction). Like an object in a closing vise the sediment layers (now rocks) are caught between two compressing plates. This is the orogenic stage. The sedimentary rocks are folded, uplifted and crushed. Magma from the upper mantle intrudes through the layers. Volcanoes erupt. The result after millions of years is a complex mountain range. Plains are wide, nearly horizontal stretches of land. Beneath the surface of plains are flat, layered rocks. Because they are flat plains are sometimes called tablelands. As with mountains, there are different types of plains. Glacial plains form when glaciers erode and deposit material over an area. Lava plains are formed by volcanoes. Alluvial (or river) plains form when rivers flood their valleys. Coastal plains form when the ocean retreats from the continent. Lake plains form when a lake dries out or drains and exposes the flat, dry lake bed. Plateaus share some characteristics of both mountains and plains. Plateaus are high like mountains - most are at least 615 meters above sea level. However, the tops of plateaus are flat like plains. Canyons and gorges usually mark their surfaces. Plateaus form when relatively horizontal rocks are uplifted. The rocks that are uplifted are not folded; instead, they remain horizontal. Plateaus often form during mountain building.

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