Note: This post has been updated and improved as of 2014 here, at the new Starts With A Bang blog. What follows, below, is the original version that was first published here.
“I love the sounds and the power of pounding water, whether it is the waves or a waterfall.” -Mike May
The world’s oceans have always been special to me, and bodies of water in general. The air smells different, the wind blows cool, and you’re reminded of the power of the salty seas every time you step in. It’s one of the reasons that the old sea shanties have always fascinated me. This week, have a listen to an updated take on that genre, as The Real McKenzies sing a cover of the more recent classic,
But there’s one ocean sight I had never seen before until earlier this week: an underwater waterfall!
Yes, off the island of Mauritius in the Indian Ocean, for all of its beauty, has what appears to be one of the most unexpected feasts for human eyes. It’s especially prominent from the air.
Even Google Maps gets in on the action!
Okay, now that you’ve seen the illusion (brought to my attention courtesy of Twisted Sifter), what’s really going on here? Obviously, water is water, and even though we can do some very clever things by manipulating fluid flow, even very cold water wouldn’t sink like this picture suggests.
Instead, there’s some really amazing and fun geology behind it!
Like many ocean islands, there are fabulous reefs off the coast of Mauritius, living ecosystems that are fascinating in their own right. But unlike many of them, Mauritius, and indeed the entire land-and-seascape around it, is very, very new on geological timescales.
Mauritius is located at the southern edge of the Mascarene Plateau, the prominent (mostly underwater) shelf located at the 11 o’ clock position in the image above. There are a few islands there, including Mauritius, which is visible (along with Réunion Island) from the International Space Station in the image below!
This oceanic shelf didn’t exist a few million years ago; sea-floor spreading created this plateau fairly recently. And there’s a huge drop-off when you leave the plateau! While most of the ocean waters around these islands is at depths ranging from 8-to-150 meters, there’s a huge plunge off that shelf into the ocean, where the depth drops to many thousands of meters!
What you’re witnessing, that looks like an underwater waterfall, is actually sand from the shores of Mauritius being driven via ocean currents off of that high, coastal shelf, and down into the darker ocean depths off the southern tip of the island.
It’s a beautiful sight that I’d love to take in with my own eyes, someday, but what’s actually going on is in many ways far more beautiful than a (physically impossible) waterfall under the ocean. It’s the natural world simply doing what it does, and we’re fortunate enough to get to not only enjoy it, but to understand it. And that’s your diversion for this weekend!