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The oceanic crust displays a pattern of magnetic lines, parallel to the ocean ridges, frozen in the basalt. A symmetrical pattern of positive and negative magnetic lines emanates from the mid-ocean ridge. [24] New rock is formed by magma at the mid-ocean ridges, and the ocean floor spreads out from this point.
Thermoremanent magnetization is the main source of the magnetic anomalies around mid-ocean ridges. As the seafloor spreads, magma wells up from the mantle, cools to form new basaltic crust on both sides of the ridge, and is carried away from it by seafloor spreading. As it cools, it records the direction of the Earth's field.
The crystallized magma forms a new crust of basalt known as MORB for mid-ocean ridge basalt, and gabbro below it in the lower oceanic crust. [16] Mid-ocean ridge basalt is a tholeiitic basalt and is low in incompatible elements. [17] [18] Hydrothermal vents fueled by magmatic and volcanic heat are a common feature at oceanic spreading centers.
Magnetic stripes are the result of reversals of the Earth's field and seafloor spreading. New oceanic crust is magnetized as it forms and then it moves away from the ridge in both directions. The models show a ridge (a) about 5 million years ago (b) about 2 million years ago and (c) in the present. [1]
The anhydrous nature of the crust on Venus prevents it from sliding past each other, whereas through the study of oxygen isotopes, the presence of water on Earth can be confirmed from 4.3 Ga. [22] Thus, this model helps provide a mechanism for how plate tectonics could have been triggered on Earth, although it does not demonstrate that ...
Scientists believe they’ve discovered an ancient ocean floor comprising a new layer between Earth’s mantle and core.
An oceanic core complex, or megamullion, is a seabed geologic feature that forms a long ridge perpendicular to a mid-ocean ridge. It contains smooth domes that are lined with transverse ridges like a corrugated roof. They can vary in size from 10 to 150 km in length, 5 to 15 km in width, and 500 to 1500 m in height.
Earth's mantle is a layer of silicate rock between the crust and the outer core. It has a mass of 4.01 × 10 24 kg (8.84 × 10 24 lb) and makes up 67% of the mass of Earth. [ 1 ] It has a thickness of 2,900 kilometers (1,800 mi) [ 1 ] making up about 46% of Earth's radius and 84% of Earth's volume.