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The Theory of Plate Tectonics, proposed in the 1960s, describes the large-scale motion of the Earth's crust, composed of seven major and numerous minor plates. These plates move at rates of approximately 2.5 cm/year. Significant geological features like the supercontinent Pangaea, which existed 500 to 200 million years ago, arose from these movements. The theory identifies three types of plate boundaries: divergent, convergent, and transform. These boundaries shape our planet, leading to phenomena such as earthquakes, volcanoes, and mountain formation.
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Theory of Plate Tectonics • Proposed in the 60’s • Describes extremely large scale motion of the plates of the earth’s crust (lithosphere) • Earth is composed of 7 major and many minor plates. • The plates move at rates of around 2.5 cm/year.
Pangaea • Existed during the Paleozoic and Mesozoic Era’s about 500 mya to about 200 mya. • Supercontinent surrounded by a giant ocean called Panthalassa.
Gondwana and Laurasia • Two supercontinents that formed after Pangaea, northern was called Laurasia southern was called Gondawana 200 to 166 mya.
Types of Plate Boundaries Divergent Convergent Transform What happens where plates meet?
Divergent Boundary • Occurs where plates are spreading apart • The main divergent boundary is in the middle of the Atlantic ocean. • This started as dry land and is now getting bigger every day
Convergent Boundaries • Occur where two plates meet • The plate that is sliding under is called the subductingplate • It melts when it goes into the liquid hot mantle and the melting crust then rises and shoots up vents to form volcanoes
Fold Mountains • Occur when two plates are colliding and causing the plate to fold. • This causes the largest mountains
Transform Boundary • Occurs when two plates try to slide by each other • Usually very earthquake prone • Example: San Andreas Fault California
Types of Plate Boundaries A. B. C. What happens where plates meet?