Tuesday, October 19, 2010

How does an atoll come into being?

Picture here isn't Fakarava, but sure is a nice example of atoll structure. All reef, no island. Coral reefs generally offer great diving. Normally, you find them in the water ringing tropical islands. But an atoll... is reef, without island. What happened? Where did the island go?

Pacific tropical islands generally start their lives as volcanoes. If the volcano erupts under water long enough, it builds an enormous subsurface mountain... that may eventually break the surface. Voila, a volcanic island. (Actually, volcanic mountaintop.)

Over aeons, that volcanic mountaintop will stop erupting, start eroding and forming soil, be colonized by bugs, birds, plants, etc and become a tropical island.

In the clear, warm water offshore, coral reefs begin to form and eventually build a ring around the island. The ring will usually be broken where rivers flow off the island into the ocean... because the silt involved retards coral growth in that area. If you are a human who wants to colonize the island with your friends in your canoe, you look for that break in the reef and paddle like crazy through it for the calm water inside.

So, all seems well. Tropical paradise, etc. But give it another few million years... and the central volcanic mass may have both eroded dramatically and sunken downwards into the crust of the earth under its own weight. One day, the island disappears again below the surface... and keeps sinking slowly.

The coral reef though is a living thing, and it continues growing. That fringing reef now sits atop the sunken volcanic island, and keeps building towards the sun while the island keeps sinking. If reef growth and island subsidence hit an equilibrium point -- known as the Darwin Point, after guess who -- an atoll results.

Friday, October 15, 2010

Et qu'est-ce qu'un Fakarava? (And what is Fakarava?)

Paddle south from Hawaii for a month or so, and you'll find the world's most poetically named island family: les Îles Sous-le-vent, or the Islands under the Wind. In English they are called the Society Islands, and of them Tahiti is perhaps the best known.

Turn left and paddle north-east from Tahiti for another week, and you'll be in the Tuamotu Archipelago. The Tuamotus comprise 76 coral atolls, scattered across an area larger than Europe.
If you are lucky, you might make landfall on an atoll called Fakarava. At last count Fakarava had a population of 701. You, tired paddler, would be number 702. Treat yourself to a coconut!

What is an atoll? This definition perfectly captures the facts while utterly missing the magic: "... a ring-shaped ribbon reef enclosing a lagoon." Really, an atoll is the coral ghost of an extinct and vanished volcanic island... and also often a very fine place for diving.

You can skip the months of paddling and choose to go by air, if you prefer. That's our plan.

Here are photos of Fakarava, from satellite and from airplane.

Thursday, October 7, 2010

Fietser et femme a Fakarava

Cycling in the Netherlands was wonderful, but the diving... nope. Too long since I've been underwater.

To remedy
the situation, Katie and I propose a trip to Fakarava in early 2011.

(Photos courtesy Fakarava cyclists)

Below this point ..."6 very unstructured weeks, on a bike, in Europe, this spring"

Below this point, my chronicle of 6 very unstructured weeks, on a bike, in the Netherlands, spring of 2010.

Above this point, something else.