The Mechanism of Changes in Mantle Volume

The crust floats above the mantle, and the volume change of the mantle is the driving force of crustal movement. The increase in mantle volume leads to crustal extensional movement, resulting in continental crust rupture and oceanic crust expansion. The decrease in mantle volume leads to crustal compression movement, resulting in continental crust superposition, folding, and oceanic crust subduction. The factors that contribute to the increase in mantle volume include a change in material state, where solid material in the mantle melts into liquid material. The factors leading to a decrease in mantle volume include: oceanic crust uplift, crustal crystallization, volcanic eruptions, magma intrusion, and hydrothermal upwelling. The change in mantle volume dominates the evolution pattern of the crust. When the mantle volume increases unidirectionally, the crust only has horizontally crystallized continental crust. When the volume of the mantle changes in both directions, blocky layered oceanic crust is formed. The expansion and subduction of oceanic crust, as well as the stretching and compression of continental crust, are the supporting mechanisms for changes in Earth’s surface area caused by changes in mantle volume.

The Model of Oceanic Crust Expansion

Oceanic crust expansion belt is the largest extensional structure on the earth. All the crustal movement theories have to face the phenomenon of oceanic crust expansion. The paper tries to interpret the phenomenon of oceanic crust expansion by the volume change of the earth and the satellite data. The oceanic crust expansion is the result of the volume change of the earth. The volume change of the earth’s mantle is the element causing the volume change of the earth;the state variation of the solid matters within the earth is the element leading to the volume increase of the earth’s mantle;while the discharge of liquid matters within the earth is the element leading to the volume decrease of the earth’s mantle. The process of oceanic crust expansion can be divided into two phases—expansion and top mounting. The phase of expansion is the volume increase of the earth’s mantle, that is, the state variation of the solid matters within the earth leading to the oceanic crust expansion. The phase of top mounting is the volume decrease of the earth’s mantle;that is, the matters of the earth’s mantle (new oceanic crust) are uplifted to be the oceanic crust matters under the action of buoyancy, which is one of the ways to discharge the matters within the earth. The expansion phase of the oceanic crust is the extensional movement period of the earth’s crust. The top mounting phase of the oceanic crust is the compressive movement period of the earth’s crust, that is, the subduction period of the oceanic crust. The speed of oceanic crust expansion is related to the state variation speed of the matters within the earth. The width of the oceanic crust expansion is related to the temperature of the seawater. The temperature of the hydrothermal flow in the oceanic crust expansion belt is related to the speed of oceanic crust expansion. The oceanic ridge terrain in the oceanic crust expansion is related to the thickness of the same density stratification above the earth’s mantle.