How Much Water is in Earth's Crust?
Earth, the "blue planet," is characterized by its vast oceans that cover 71% of its surface. This massive amount of water is the lifeline of the planet, facilitating human, animal, and plant life throughout. However, along with the water on its surface, the Earth holds extensive amounts of water within its crust. This subterranean water plays a crucial role in geological processes and is vital for the planet's water cycle. From cooling magma to influencing the movement of tectonic plates, it serves various important purposes. While it was unsure how much water is in the crust, recent advancements in geological research have provided new insights, and scientists now believe that the figure is greater than 10 million cubic miles.
The Earth's crust is the outermost layer of the planet, lying above the mantle and divided into two distinct types: the continental crust and the oceanic crust. The continental crust is the outermost layer and is quite thick, with an average thickness of about 24 miles (40 km). It primarily comprises granite and other light silicate minerals, making it lighter than its counterpart. In contrast, the oceanic crust is thinner and denser, with an average thickness of 4 miles (6 km). The topmost part of this crust mainly consists of basalt and lavas made from it. The interaction of water with these crustal materials significantly affects their chemical compositions and physical properties.
Water enters the Earth’s crust through various routes. Rainfall and surface water seep into the soil, filtering down through layers of rock via pores and fractures to replenish groundwater in aquifers. These aquifers are crucial sources of freshwater stored in permeable rock formations. Furthermore, tectonic activities such as subduction, where oceanic crust slides beneath the continental crust, and processes at mid-ocean ridges where new crust is formed allow significant amounts of water to be transported deep into the Earth.
