Final answer:
The theory of plate tectonics describes how large segments of Earth's crust, driven by convection within the mantle, move over time, forming geological features like mid-ocean ridges and deep-sea trenches. This theory was a development from Alfred Wegener's concept of continental drift, suggesting continents once formed a supercontinent Pangaea. Volcanoes, prevalent at mid-ocean ridges and subduction zones, provide evidence for this theory, revealing material from deep within Earth.
Step-by-step explanation:
The theory of plate tectonics posits that the Earth's crust and upper mantle are divided into large segments or 'plates' that move over time. These movements result from convection within the Earth's mantle, where heat from the interior rises, driving the plates. Plates can move apart, like at the Mid-Atlantic ridge (a rift zone) where molten rock from below fills the gap, forming features such as mid-ocean ridges. On the other hand, when plates are forced together, subduction zones and features like deep-sea trenches can form.
German scientist Alfred Wegener proposed the concept of continental drift, an early precursor to plate tectonics theory, suggesting that the continents were once united in a supercontinent called Pangaea. His theory, however, lacked a compelling mechanism to explain how the solid continents could move across the globe. It took many years and further scientific progress in geology, oceanography, and geophysics to develop the theory of plate tectonics we understand today.
Volcanoes provide another evidence for plate tectonics, as they mark locations where lava rises to the surface, such as at mid-ocean ridges and subduction zones - revealing material from deep within our planet.
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