The idea of an "underwater sea inside Earth three times the volume of water on the surface" is often associated with a concept called the "water cycle of Earth's mantle." This theory proposes that there could be vast amounts of water trapped deep within the Earth's mantle.
Here's a breakdown of this concept:
Water in the Mantle: Some scientists believe that significant amounts of water may exist in the Earth's mantle, which is the layer between the crust and the core. This water is theorized to be trapped in minerals in the mantle.
Subduction Zones: Water can enter the mantle through subduction zones, where tectonic plates converge and one plate sinks beneath another. Water-containing minerals from the descending plate release water as they heat up and undergo chemical changes in the mantle.
Water Cycle of the Mantle: This concept suggests that water cycles through the mantle in a process similar to the water cycle on the Earth's surface but on a much longer timescale and involving geological processes.
Estimating Water Volume: The idea of an underwater sea three times the volume of water on the surface is a theoretical estimation based on geological models and the amount of water believed to be present in the mantle.
However, it's essential to note that this concept is still under scientific debate and investigation. While there is evidence supporting the presence of water in the mantle, the exact amount and distribution remain uncertain. Research and advancements in geology and geochemistry continue to shed light on the complex dynamics of water within the Earth.