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Автор: Alexander E.Gates, David Ritchie
Издательство: Facts on File
Год издания: 2007
isbn: 0816063028
Количество страниц: 365
Язык: english
Формат: PDF
Размер: 18 Мб
Каталожный номер: 52640
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The Earth is a sphere that is flattened at the poles and bulging at the equator. Internally, it is like a hard-boiled egg. In the center, instead of a yolk, it has a core. The core is composed of iron-nickel and contains an inner core that is solid and an outer core that is liquid. The spinning of the Earth causes the two to interact as a self-exciting dynamo that gives Earth its strong magnetic field. The egg white is equivalent to the Earth’s mantle, which encases the core. The mantle is composed of dense minerals that are rich in iron and magnesium. It has several layers reflecting different minerals and mechanical properties. The shell of the egg is equivalent to the Earth’s crust, a thin layer of light rock upon which humans live. Unlike the shell, which is uniform, there are two types of crust. Thin, dense, young crust is pulled toward the center of the Earth by gravity and sinks down, whereas thick, light, old crust floats higher. The deeper crust is covered by oceans and called oceanic crust, whereas the lighter crust forms the continents and is called continental crust. The concept of isostasy is the balance between them.
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