Fig. 45 Three types of plate boundaries
Geophysicists also talk of active margins (where colliding continental and oceanic plates spark off volcanic eruptions, earthquakes and mountain building) and passive margins (tectonically quiet boundaries between continental and oceanic crust).
(Lambert “The Field Guide to Geology” 1988, Cambridge University Press)
Discussion questions:
1. What comprises the Earth’s surface?
2. What is a plate?
3. What do the plates make up?
4. What shifts the plates?
5. How many types of plate margins are there?
6. What is
- a constructive margin -a destructive margin -a conservative margin
7. What is the difference between active and passive margins?
8. The map shows major plates. Name them.
PART 2: CONTINENTAL CRUST
COMPREHENSION 1.1 Vocabulary
Pay attention to the pronunciation of the geographical terms and especially to the pronunciation of numbers (R.P.-8.2.3)
Tethyan (Alpine-Himalayan) Aleutian Islands
Circum-Pacific The Andes
Ural Mountains The Alps
Cordillera
Pay attention to the terms and expressions in bold
plateau плато, плоскогорье
range (ranges) горный хребет (горная страна)
mountain chain (range) горная цепь
mountain system горная система
orogenesis орогенез; горообразование
to disrupt нарушать
mobile belt подвижный пояс
lithospheric plate литосферная плита
crustal deformation деформация земной коры
mountain building горообразование
orogen ороген, горно-складчатое сооружение
orogenic орогенический; горообразующий
uplift поднятие (участка земной коры)
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to weld (together) соединять
scrap скрап; обломок
to sweep перемещать; сносить
terrane террейн
to squeeze сдавливать; выжимать
to bob up возникать
to ruck up нагромождать, собирать(ся) складками
to shrink сокращать
alien rock «чуждые» породы
MOUNTAIN BUILDING (R.P – 8.2.7, 8.2.8, 8.2.9)
Large regions of the Earth consist of mountains. Most occur in rows called ranges. Parallel ranges and intervening plateaus form chains such as the Andes and North American Cordillera. Related mountain chains and ranges make up mountain systems, notably the Tethyan (Alpine-Himalayan) and Circum-Pacific systems.
Orogenesis, or mountain building, occurs along mobile belts – places where colliding lithospheric plates disrupt the continental crust. Such mountain-building belts are known as orogens and orogenic belts are belts of fold mountains – mountains created by crustal deformation and uplift. Geologically recent orogenic belts mostly rim continents. But ancient orogenic belts (the Ural Mountains for example) can occur deep inside a continent where lithospheric plates were welded together long ago.
Fig. 46 Mountain building
Mountain building is a complex process. Deep troughs of accumulated offshore sediment, volcanic rocks, bits of oceanic crust, and scraps of foreign continents can all be swept against one continent and welded on as mountain ranges. Most of mountainous western North America consists of more than 50 suspect terranes – mighty slabs of alien rock that independently rotated and migrated north along the western edge of North America.
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Here are three major mountain-building processes. 1. Oceanic plate subduction below another oceanic plate – this process created the Aleutian Islands and other mountainous island arcs.
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