Tag Archives: atoll

Typical atoll in the Tuamotus

The Tuamotu Archipelago

The Tuamotus archipelago is the widest of the five French Polynesia archipelagos.  Makatea and the 4 Gambier islands are the only high islands.  However, the remaining 83 motus or atolls are not actually islands.  Only 6% (roughly 19,000) of the Tahitian population live in this region, which is surprising considering it has the most islands and covers the widest area.

Tuamotus (Image from Google Images)

Tuamotus (Image from Google Images)

This region is famous for its colorful and perfect pearls (Gambiers).  However, its first quality is the purity and wealth of the underwater world.

The Tuamotus were named “the dangerous archipelago” because of their hazardous passes and abundant coral heads “bombies.”  The first European settlers aptly named the region because of the immense risks it presented to the ships during that era.  Alternatively, today, many vessels visit the area thanx to navigational charts and Google Earth.

Google Earth will give you high level images of the archipelago. As well as many other images (as you know).

Google Earth Image of Tuamotus

Google Earth Image of Tuamotus

In addition, you can zoom in to see a particular region.

Google Earth Islands

Google Earth Islands

Alternatively, you can zoom in to see a specific motu.  You can even zoom in enough to see the coral heads.

Google Earth image of Tikehau

Google Earth image of Tikehau

The archipelago is divided into the Western and Eastern islands.  The western islands were discovered long before the Society Islands.  The Spanish navigators discovered them in 1605 and then the Dutch in 1616.  However, despite these discoveries, it took an additional 230 years for the world to learn about this archipelago.  The whaling captains plowed through these seas refusing to talk about them.  Probably trying to protect their fishing zones. Because discovering an island was not a priority.

Easter Tuamotus

Explorers left the Eastern Tuamotus mostly undiscovered.  That is until the The French Government decided to put the Centre d’essai du Pacific Experimentation Center (CEP) in these atolls in 1960.  Which is just a fancy name for nuclear testing facility.  These tests continued for 33 years before it was shut down in 1996.

By way of example, a typical Tuamotu island will look like the photo below.  In particular, with a reef surrounding the motus and a lagoon in the center.

Typical atoll in the Tuamotus

Typical atoll in the Tuamotus

Islands we have already visited in the Tuamotus (as of 22 Sept. 2019)

  • Hao
  • Makatea
  • Tikehau
  • Rangiroa
  • Hao

Islands we hope to visit in the Tuamotus:

  • Apataki
  • Kauehi
  • Fakarava
  • Tahanea
  • Makemo
  • Ahe
  • Amanu
  • Manehi

Considering the above list, if we were to hit all of those islands, we would have visited all of the passable atolls in the Tuamotus.  The fact that it is the largest archipelago, that is a huge feat.

Making of an atoll

The Making of an Atoll: The Subsidence Phenomenon

Every single island in the Tuamotus, and a few islands in the other archipelagos, are atolls.  So, what is an atoll?

An atoll begins to form when a volcanic island becomes inactive.  All of the islands in French Polynesia are slowly sinking and moving west.  Some have just been sinking a lot longer than others.  The volcanic islands in the Tuamotus are some of the oldest in the region.

The volcanic island sinks or subsides under its own weight.  At the same time, a coral reef forms around the island.  This takes about 6 million years.  The coral reef can be between 0 and 200 meters deep.  Anything deeper than 200 meters soon dies as it does not have enough light to survive. 

Over time, the volcanic mountain disappears completely.  The coral proliferates as the volcano slips into the ocean.  New colonies spring up on the skeletons of the old ones, constantly renewing the calcareous crown of the surface.  Eventually, what remains of the mountain is an underwater basalt platform covered with a thick calcareous crust.

This display is a good example of the making of an atoll.  The image up front shows the volcano, the center shows the mountain sinking and the furthest one is an atoll.

Making of an atoll

Making of an atoll

Typically, there is a passe that allows vessels to enter the lagoon that is surrounded by the coral reef.  Some atolls have no passe which makes them impossible to visit.  Other atolls have a dangerous passe which has to be navigated during a certain time (slack tide) to avoid damaging your vessel.

Teti’aroa’s atoll

Teti’aroa has no passe.  There is no way to bring the big boat into the protected lagoon.  However, there are 5 mooring balls located near the reef buried in over 50 meters of water.  We were able to secure one of these moorings.  The photo below is from our Navionic app which shows a light gray reef all the way around the atoll.  The yellow spots indicate the motus or islets and the blue (inside the gray) is the lagoon.  The gray represents the coral around the motus.

Teti'aroa motus

Teti’aroa motus