Continental Drift and World Ocean Level Variations

Аннотация

The ocean level fluctuations relative to continents are caused by both physical processes related to water volume variations and tectonic processes related to changes in the bottom topography. Currently, the main tectonic causes are considered to include the occurrence of midocean ridges and variations in an expansion velocity of the ocean floor with the corresponding rise or fall of the bottom. The specific role of continental drift is not taken into account, or it is given a passive role. This work demonstrates the important role of continents in long-term changes in the ocean level. The numerical model shows the influence of continents on tectonic activity of the mantle and continents “floating” over the mantle with uneven relief, which cause relative variations in the ocean level. While the continent is above the ascending mantle stream, it is raised, and the ocean level relative to the continent falls. After the supercontinent split, the continents diverge, and the ridge previously covered by continents occurs in the ocean. Being close to subduction zones, the continents subside thus increasing the relative ocean level. The model also shows that the continents do not move strictly horizontally along the mantle, but, like floating ships, change their slope depending on the mantle relief.