A groundbreaking discovery by Northwestern University researchers reveals an enormous water reservoir deep beneath the Earth's surface, fundamentally altering our understanding of the planet's water origin. This vast underground ocean, found approximately 700 kilometers below us, challenges previously held notions about the Earth's water, suggesting it may have emanated from the planet's interior rather than being introduced from extraterrestrial sources.

The study, published in 2014 and titled "Dehydration melting at the top of the lower mantle," offers compelling evidence of the reservoir's existence within a type of blue rock known as ringwoodite. This mineral, situated in the Earth's mantle—the hot, dense layer of rock between the crust and the core—has the remarkable ability to store water within its structure. The mantle acts as a colossal sponge, holding water in the form of hydrogen and hydroxide ions.

Steven Jacobsen of Northwestern University, who played a pivotal role in the research, conveyed to New Scientist the significance of the discovery, emphasizing its implications for our understanding of Earth's water cycle. The existence of such a reservoir supports the theory that Earth's surface water originated from within, seeping out over time to form oceans.

The researchers utilized a network of 2000 seismometers to analyze the seismic waves generated by over 500 earthquakes. These waves, which travel through the Earth's interior and can be detected at the surface, provided invaluable insights into the subterranean world. By observing variations in wave speed at different depths, the team could identify the presence of dampened rock, indicating water.

This method of investigation highlights the dynamic and interconnected nature of Earth's layers, offering a glimpse into deep geological processes. Jacobsen likened the planet's reaction to seismic waves to a bell that continues to resonate long after the initial event, a phenomenon that allowed for the detailed analysis of the underground landscape.

The discovery not only enriches our understanding of Earth's geology but also carries profound implications for the global water cycle. According to Jacobsen, without this deep reservoir, Earth's surface would be vastly different, with significantly higher sea levels covering much of the land. This hidden ocean, therefore, plays a crucial role in maintaining the balance of water on and within our planet. It could very well be that the oceans we know are actually LEAKAGE of this proto-ocean, a huge body of water coming from inside the earth. 

Above is the traditional section of what we THOUGHT Earth's mantle and core looked like. Now imagine that between the different parts is a huge body of water, slowly leaking out to the oceans we know.

Supporting evidence from a separate 2014 study by the University of Alberta researchers further solidifies the findings. They analyzed a diamond expelled from deep within the Earth by a volcano, which contained traces of water-bearing ringwoodite. This additional proof underscores the prevalence of water in the Earth's mantle, specifically within the transition zone—a region characterized by dramatic shifts in temperature, pressure, and mineral composition, located between the upper and lower mantle.

Together, these studies revolutionize our comprehension of Earth's water sources, suggesting a much more complex and internally driven water cycle than previously thought. The existence of such an immense subterranean ocean opens new avenues for research, potentially reshaping our approach to studying Earth's geological and hydrological phenomena.