Brandon Dugan, a petrologist with the Colorado School of Mines, says that in some places the water began pooling more than 100,000 years ago, when meltwater from glaciers filled offshore water tables and was eventually sealed in by sediment as sea levels rose. In other places, the water arrived much more recently through rainfall and natural pipelines from land-based aquifers.
“Glacial water is old and has a distinct chemical composition; water connected to land-based systems has a different one,” says Dugan. “The composition can tell us how fresh water gets distributed below the seafloor. So, once you get an idea of how the water was emplaced, you’ll know where it is likely to flow and where it likely won’t. This helps us understand how to develop it as a resource.”