plate tectonics: a standalone construct

Alfred Wegener's 1912 lectures and his 1915 book Die Entstehung der Kontinente und Ozeane (The Origin of Continents and Oceans) proposed continental drift, the idea that the continents were once joined and have since moved across Earth's surface, though he could not explain the driving force and the idea was long resisted. The modern theory of plate tectonics took shape in the 1960s, when the confirmation of seafloor spreading by Fred Vine and Drummond Matthews (1963), who showed that magnetic stripes on the ocean floor record the reversing magnetic field as new crust forms and spreads outward, was combined by Dan McKenzie and Robert Parker (1967) and by Jason Morgan (1968) into a description of Earth's outer shell as a set of rigid plates moving on a sphere. In this theory the lithosphere, the rigid outer layer of rock, is broken into about a dozen large plates that ride slowly over the weaker, partly yielding asthenosphere beneath, at roughly the rate fingernails grow. Where plates pull apart new ocean crust is created, where they collide crust is destroyed or crumpled into mountains, and where they slide past one another strain builds and releases, so the theory accounts in one framework for the global pattern of earthquakes, volcanoes, mountain belts, ocean basins and the fit of the continents.[1][2][3][4]

Unit

A unifying geophysical theory whose unit of analysis is the rigid plate and the three kinds of boundary between plates

Recovery means

Not applicable

Measured by

Plate motions are identified from ocean-floor magnetic anomaly stripes, transform-fault geometry, the global distribution of earthquakes and their focal mechanisms, and are measured directly by space geodesy such as GPS