Sunday, 1 June 2014

Underwater Water

The thought of an underwater lake or river initially appears completely absurd, yet they are as real as the mountains and fields that surround us on land. These lakes and rivers are equipped with shorelines and trees, and even flow and move independently of the water around them. On the surface this whole concept appears to defy logic, but as with all things, there is always an explanation.

Cave diving is one of the most dangerous and extreme sports in the world, yet the call to this sport can be strong. Budding explorers and adrenaline junkies may flock to this activity and risk their lives in the process, because the underwater caving systems of the lakes, seas and oceans that cover 72% of the earth (roughly 326 million trillion gallons) have yet to be fully explored by human kind. It is within one of these caving systems in the Gulf of Mexico where a fully functioning underwater river was discovered. This river has fully established banks that are lined with logs, trees and leaves, yet the water that flows along this underwater river is of a different colour and consistency to that which surrounds it. The water contained within underwater lakes and rivers has a much higher level of salinity than that of ocean or sea water. This makes the water denser which enables it to completely separate itself from the surrounding water, giving it the ability to flow independently. Quite often the water of these lakes and rivers also contains a high level of hydrogen sulfide which generates a strong rotting egg smell, very similar to that of our underground sewers. Underwater lakes - commonly referred to as Brine Lakes or Cold Seeps - are a hotbed for life. The most famous of these underwater lakes can be found 650 ft underwater within the Gulf of Mexico, close to the Chicxulub crater. When this 20 meter lake is viewed from a distance the lake appears to have a distinct rocky shoreline, but upon closer inspection it becomes apparent that what you once thought were rocks are actually hundreds of thousands of mussels. However, due to the hypersalinity of the lake's and river's waters, very little can survive with the exception of Mollusks and Crustaceans that have evolved to live in a methane and hydrogen sulfide rich environment, without any need of sunlight. In fact, crabs and urchins have been found literally pickled within their waters. 

It is believed that the formation of these underwater lakes and rivers began in the Jurassic period, which occurred between 201 million and 145 million years ago. During the Jurassic period the Gulf of Mexico is believed to have been covered with very little water. This water soon dried out which lead to the creation of pockets of salt and other minerals. When the water returned the super-saline layer at the bottom of the Gulf became an underwater lake, and the brine that is still contained within the ocean floor feeds that lake from below.

A SCUBA diver swimming along the length of an underwater river lined with trees and leaves.

Hundreds of thousands of Mussels creating a 'pebble like' shoreline on an underwater lake in the Gulf of Mexico. The water is so salty that to most species the whole lake is an uninhabitable area.  

Cave divers exploring an underwater cave network. This is one of the most dangerous sports in the world. It isn't hard to understand why.

- Until the next Butterfly...