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The Pacific plate (carrying the city of Los Angeles) is moving northwards with respect to the North American plate. The Queen Charlotte Fault on the Pacific Northwest coast of North America The Motagua Fault , which crosses through Guatemala , is a transform boundary between the southern edge of the North American plate and the northern edge of ...
Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') [1] is the scientific theory that Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.
Evidence from paleomagnetism led to the revival of the continental drift hypothesis and its transformation into the modern theory of plate tectonics. Apparent polar wander paths provided the first clear geophysical evidence for continental drift, while marine magnetic anomalies did the same for seafloor spreading .
The Juan de Fuca and Gorda plates are moving east-northeast, subducting under the North American plate at a much slower rate of 2.5 to 3 cm per year. [6] Because the ridge is divided into three distinct parts, each section has its own spreading rate, caused by the slab-pull and ridge-push of the surrounding tectonic plates .
Where the plates meet, their relative motion determines the type of plate boundary (or fault): convergent, divergent, or transform. The relative movement of the plates typically ranges from zero to 10 cm annually. Faults tend to be geologically active, experiencing earthquakes, volcanic activity, mountain-building, and oceanic trench formation.
Instead of the ridges moving away from each other, as they do in other strike-slip faults, transform-fault ridges remain in the same, fixed locations, and the new ocean seafloor created at the ridges is pushed away from the ridge. Evidence of this motion can be found in paleomagnetic striping on the seafloor.
Map showing approximate location of many current hotspots and the relationship to current tectonic plates and their boundaries and movement vectors The origins of the concept of hotspots lie in the work of J. Tuzo Wilson , who postulated in 1963 that the formation of the Hawaiian Islands resulted from the slow movement of a tectonic plate ...
Mauna Loa is the classic example, with a slope of 4°-6°. (The relation between slope and viscosity falls under the topic of angle of repose . [ 12 ] ) A composite volcano or stratovolcano has a more steeply rising cone (33°-40°), [ 13 ] because of the higher viscosity of the emitted material, and eruptions are more violent and less frequent ...