The global volume of freshwater stored in the seafloor is 500,000 cubic kilometres – a volume larger than that extracted by humans in the past 200 years. To get a better idea of this volume, it is roughly a sixth of the volume of the Mediterranean sea. The occurrence of freshwater in a predominantly saltwater environment may be baffling, yet geology can play some really cool tricks when it comes to the transfer and storage of freshwater across the surface of our planet.

One simple way in which freshwater can be stored underwater is by having a body of groundwater locked on the surface with an underwater penetrable layer linked offshore via a geological layer such as sedimentary rock.

Such groundwater bodies tend to become thinner with increasing distance from the coast and are associated with water seeping through the seafloor, a process called seepage.

Offshore freshwater seepage has been known for centuries. During Roman times, some sites, such as offshore Lebanon, were very popular with seafarers, who used to replenish their freshwater supplies by lowering a bucket into the sea.

A second way in which freshwater can occur offshore is via the development of fossilised groundwater bodies. During most of the past 2.5 million years, the sea level has been lower than it is today by up to 130 metres. This exposed vast areas of the ocean floor, where rainwater infiltrated into the ground. Groundwater bodies developed in this way became trapped underwater after sea levels rose again.

The study of offshore groundwater systems is an exciting scientific frontier. Offshore groundwater could provide a new and important source of freshwater for cities and islands where water is scarce, polluted or will be impacted by future climate change. Offshore groundwater seepage also controls the nature of seafloor ecosystems and affects ocean chemistry.

A key challenge is finding where offshore groundwater occurs. To address this issue, the University of Malta’s Department of Geosciences will soon start a five-year project studying groundwater systems offshore New Zealand and the Maltese islands.

Did you know…

• The Blue Whale is the largest animal on earth, even larger than the largest of the dinosaurs.

• If you exposed a glass of water to space, it would boil rather than freeze. However, the water vapour would crystallise into ice afterward.

• A lightning strike can reach a temperature of 30,000˚C.

• Rain occurs on other planets in our solar system but it is different to the rain we experience on earth. For example, rain on Venus is made of sulfuric acid and due to the intense heat it evaporates before it even reaches the surface.

For more trivia: www.um.edu.mt/think

Fact bites

• Graphene is an engineered material at the heart of the nanotechnology revolution. It is very strong and highly absorbent of light shown on its surface. Researchers at the University of Surrey have now made very thin graphene-based sheets that can harvest the sun’s energy.

Strangely enough, these solar sheets borrow certain engineering characteristics from the moth eye structure. The amazing thing about this discovery is that these sheets do not need to be outside since they are so efficient. This may open the door to more discreet forms of solar energy.

www.digitaltrends.com/cool-tech/moth-eye-graphene

• In 2012, Google unleashed its first driverless car which quickly expanded, as a programme, into a small fleet of cars currently being tested on the road. They have, so far, gone more than two million kilometres on the road with no major hiccups yet. Last month one of the cars crashed into a bus but luckily it was only going at 2mph. Despite this, the Google car has shown great promise in leading the way in driverless car technology.

http://www.bbc.com/news/technology-35800285