What is the theory of plate tectonics?

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Accepted Answer

The theory that Earth's outer shell is divided into several plates that glide over the asthenosphere, interacting at their boundaries to produce earthquakes, volcanoes, and mountain building. The theory of plate tectonics states that Earth's outer shell (lithosphere) is divided into approximately 15 major and several minor tectonic plates that float on and glide over the semi-plastic asthenosphere beneath them. These plates move slowly (typically 2-10 cm per year) and interact at three types of boundaries: divergent (plates moving apart, creating new crust), convergent (plates colliding, causing subduction or mountain building), and transform (plates sliding past each other). These interactions produce most of Earth's earthquakes, volcanic activity, and mountain belts.

The claim that Earth has a single continuous plate contradicts the fundamental premise of plate tectonics, which is that the lithosphere is broken into multiple independent plates. The assertion that continents have always been in their current positions contradicts the evidence for continental drift, originally proposed by Alfred Wegener, which was later incorporated into plate tectonic theory. The idea that Earth's surface is being eroded away to nothing ignores the balance between destructive and constructive geological processes.

Plate tectonics is the unifying theory of geology and is heavily tested on the DSST Introduction to Geology exam. Students should understand the three types of plate boundaries and their associated geological features, the evidence supporting plate tectonics (seafloor spreading, magnetic reversals, fossil distributions, continental fit), the driving mechanisms (convection currents, ridge push, slab pull), and how plate tectonics explains the distribution of earthquakes, volcanoes, and mountain ranges.

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