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The Structure and Composition of Tectonic Plates

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Explore the structure of tectonic plates, comprising Earth's lithosphere with oceanic and continental crusts. Learn about their categorization into major, minor, and microplates, and the interactions at plate boundaries that lead to geological phenomena such as earthquakes and volcanic eruptions. Understand the role of different plate sizes in shaping the Earth's surface and their contribution to the planet's dynamic history.

The Structure and Composition of Tectonic Plates

Tectonic plates are the large, rigid slabs of Earth's lithosphere, which is composed of the crust and the uppermost part of the mantle. These plates vary in thickness, typically ranging from 50 to 150 kilometers. The lithosphere is divided into two types of crust: oceanic and continental. Oceanic crust, made of dense basaltic rocks rich in silicon and magnesium (referred to as sima), is thinner and more malleable than continental crust. Continental crust, composed of lighter granitic rocks that contain more silicon and aluminum (termed sial), is thicker and less dense. The composition and behavior of these crusts are fundamental to understanding the movement of plates and the resulting geological phenomena.
Natural landscape with visible fault dividing layered rock formations and green valley, under blue sky with snow-capped mountains.

Categorization of Tectonic Plates

Tectonic plates are classified by size into three categories: major, minor, and microplates. Major plates, such as the North American and Pacific plates, cover areas greater than 20 million square kilometers and are the principal drivers of global tectonics. Minor plates, like the Nazca and Cocos plates, have areas between 1 and 20 million square kilometers and often interact with major plates at their boundaries. Microplates, the smallest category, cover areas less than 1 million square kilometers and can significantly influence local tectonic activity. The Earth's lithosphere may be composed of numerous microplates, which, when considered together, form a complex and interlocking pattern that affects the planet's geodynamics.

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00

Tectonic plates have varying thicknesses, generally between ______ to ______ kilometers.

50

150

01

The Earth's lithosphere is categorized into two types of crust: ______ and ______.

oceanic

continental

02

______ crust is composed of dense basaltic rocks, also known as sima, and is more malleable than its counterpart.

Oceanic

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