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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. [5] Faults tend to be geologically active, experiencing earthquakes, volcanic activity, mountain-building, and oceanic trench formation.
Deep sea mining is the extraction of minerals from the seabed of the deep sea. The main ores of commercial interest are polymetallic nodules, which are found at depths of 4–6 km (2.5–3.7 mi) primarily on the abyssal plain.
Map showing Earth's principal tectonic plates and their boundaries in detail. These plates comprise the bulk of the continents and the Pacific Ocean.For purposes of this list, a major plate is any plate with an area greater than 20 million km 2 (7.7 million sq mi)
The Vine–Matthews–Morley hypothesis, also known as the Morley–Vine–Matthews hypothesis, was the first key scientific test of the seafloor spreading theory of continental drift and plate tectonics. Its key impact was that it allowed the rates of plate motions at mid-ocean ridges to be computed.
Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental crust , or sial , generally less than 10 kilometers thick; however, it is denser, having a mean density of about 3.0 grams per cubic centimeter as opposed to continental crust which has a density of about 2.7 grams ...
The two major resources mined at sea include oil and minerals. Over the last 30 years, deep-sea mining has generated between $9 -$11 billion USD in the United States of America. [43] [44] Although this sector seems profitable, it is a high risk, high reward industry with many harmful environmental impacts. [45]
Plate tectonics was a suitable explanation for seafloor spreading, and the acceptance of plate tectonics by the majority of geologists resulted in a major paradigm shift in geological thinking. It is estimated that along Earth's mid-ocean ridges every year 2.7 km 2 (1.0 sq mi) of new seafloor is formed by this process. [50]
The Juan de Fuca plate sinks below the North America plate at the Cascadia subduction zone The simplified model of mantle convection: [5] Oceanic plates are subducted creating oceanic trenches. According to the theory of plate tectonics , the Earth's lithosphere , its rigid outer shell, is broken into sixteen larger tectonic plates and several ...