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We can divide the processes that alter the earth

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We can divide the processes that alter the earth's surface into two categories: 1) igneous processes (volcanism and mountain building) construct features by increasing the average elevation of the land, 2) Sedimentary and erosive processes (deposition and weathering) act as forces wearing down features created by volcanoes and creating new horizontal features (e.g. river delta). The theory of Plate tectonics provides a synthetic model for understanding how the dynamics of the earth work. The plates move around, collide, move over or under one another. Divergent boundaries are where plates move apart, convergent boundaries are where plates move toward one another, transform boundaries (e.g. San Andreas fault) are where plates move by each other. The continental plates (lithosphere) float on molten inner layer (asthenosphere). Where plates meet there can be uplifting or subduction. Uplifting
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Unformatted text preview: results in mountain building through igneous activity and at the boundaries between plates and actual scraping off of material from the subducted plate. Subduction results in plates being forced downward and is seen is formations such as ocean trenches. The rock material of continental plates can be viewed as going through a rock cycle that can be related to plate tectonics. Magma (molten rock) e.g., released from volcanoes, crystallizes and forms igneous rocks ("fire formed rocks"). Through weathering and transport sediment is formed which by lithification become sedimentary rock. Through exposure to high temperatures and pressure, sedimentary rock (or any rock) can be changed into metamorphic rocks . If this rock is exposed to extreme temperatures it can become molten again and form magma, and if released through volcanic activity be reintroduced as igneous rock....
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