The technological advances leading to the extraction of shale gas and shale oil are revolutionizing the world’s energy markets. Now, the discovery of vast quantities of low-salinity water under Earth’s continental shelves is further evidence that occurrences of future natural resources are unpredictable, their limits bounded only by human innovation and discovery.
In a report published in the December 5 issue of Nature (“Offshore fresh groundwater reserves as a global phenomenon”), Post et al.1 estimate the cumulative volume of the newly identified water bodies, (referred to as Vast Meteoric2 Groundwater Reserves, or “VMGRs”), at about 500,000 cubic kilometers, an amount roughly 100 times greater than the volume of water extracted from the Earth’s sub-surface since 1900. In an Environmental News Service article3, lead researcher and groundwater hydrologist Dr. Vincent Post of Australia’s Flinders University is quoted as saying, “Knowing about these reserves is great news because this volume of water could sustain some regions for decades.” Dr. Post explained that “freshwater under the seabed is much less salty than seawater. This means it can be converted to drinking water with less energy than seawater desalination, and it would also leave us with a lot less hyper-saline water.” That is truly great news for regions of the world with growing populations in need of drinking water.
Buried at Sea
The authors suggest that the continental VMGRs became trapped beneath the seafloor in the geologic past during the last Ice Age, some 20,000 years ago, when sea level was lower than it is today, and greater areas of coastal land masses were exposed. These vast underground aquifers were charged with fresh water as precipitation filtered through rock and sediment layers over the course of thousands of years. As the last Ice Age came to an end, sea level rose, burying former coastal areas and forming what we refer to today as “continental shelves.” In many places along the continental shelves buried aquifers were isolated from seawater and preserved by impervious layers of clay and other sediments.
Accessing VMGRs by drilling could be accomplished, according to Dr. Post, either by building a platform out at sea and drilling into the seabed or drilling from the mainland or islands near the aquifers. According to the Nature article, Cape May, a coastal community at the southern tip of New Jersey, has been extracting water from a VMGR on the Atlantic continental shelf since 1998. Once extracted, VMGRs will not be replenished until sea level falls again and currently submerged land masses are re-exposed, so this resource is considered “renewable” only on a very long time scale. However, we must remember that the common view of Earth resources as products of nature alone is mistaken: as we have learned from the shale fuel phenomenon, the total inventory of any Earth resource is dynamic, and resources occur at the intersection of geological phenomena, on the one hand, and human innovation and entrepreneurship, on the other.
The recent discovery of vast water resources under Earth’s continental shelves parallels a tenet of the philosopher of science Karl Popper, who once wrote, concerning mineral resources, “The total supply of any mineral is unknown and unknowable because the future knowledge that would create mineral resources cannot be known before its time.”4 This valuable perspective is both enlightening and exhilarating as we tackle the challenges of alleviating poverty, and continue to improve the quality of human life on Earth.
Philip A. Candela, Ph.D., is Professor of Geology at the University of Maryland, and is a physical geochemist specializing in economic geology, resources and security.
1Post, V.E.A., Groen, J., Kooi, H., Person, M., Ge, S. and Edmunds, W.M. (2013), “Offshore fresh groundwater reserves as a global phenomenon,” Nature 504, 71-78.
2Meteoric water is groundwater that originated as precipitation.
3Vast New Freshwater Sources Found Beneath the Sea, Environment News Service, December 5, 2013. Online: http://ens-newswire.com/2013/12/05/vast-new-freshwater-sources-found-beneath-the-sea/ (accessed December 10, 2013).
4Popper, K. (1957). The Poverty of Historicism. New York: Harper.