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Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. [1] [2] The crust overlies the rigid uppermost layer of the mantle.
The conventional view that marine magnetic anomalies arose in the upper, extrusive layer of the oceanic crust requires a rethink because perfectly normal magnetic anomalies arise at core complexes, where the crust has been stripped away. This suggests that the lower part of the ocean crust contains a substantial magnetic signature.
Magnetic anomalies off west coast of North America. Dashed lines are spreading centers on mid-ocean ridges. The Vine–Matthews-Morley hypothesis correlates the symmetric magnetic patterns seen on the seafloor with geomagnetic field reversals. At mid-ocean ridges, new crust is created by the injection, extrusion, and solidification of magma.
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Manganese layers typically form at higher redox potentials compared to iron layers, but a period of rapid increase in redox potential can form a mixed layer. [2] As the nodules are formed, trace elements including but not limited to nickel, cobalt, copper, and zinc are incorporated. [ 2 ]
Scientists believe they’ve discovered an ancient ocean floor comprising a new layer between Earth’s mantle and core.
A wealth of new information about Earth’s inner core has surfaced in recent months. Scientists now have evidence that the planet’s innermost layer is changing shape.
Fluid motions occur in the magnetosphere, atmosphere, ocean, mantle and core. Even the mantle, though it has an enormous viscosity, flows like a fluid over long time intervals. This flow is reflected in phenomena such as isostasy, post-glacial rebound and mantle plumes. The mantle flow drives plate tectonics and the flow in the Earth's core ...