!!!French Polynesis. Part IV. Rangiroa

Photos and text by [Ádám Plézer|https://plezeradam.com],
member of the [AirPano Team|Geography/About/Consortium/AirPano,_Team] that is a member of the [global-geography Consortium|Geography/About/Consortium]. \\

20 January 2021

with kind permission of [AirPano|http://www.AirPano.com]

Rangiroa, French Polynesia

Rangiroa (Tuamotuan for 'vast sky') is the largest atoll in the Tuamotu
archipelago and one of the largest in the world. The atoll consists of
about 415 motus, islets and sandbars comprising a total land area of
about 170 km². There are approximately one hundred narrow passages
(passes), called hoa, in the fringing reef. The lagoon has a maximum
depth of 35 m and it is so large that it has its own horizon. Due to its
shallow depth, the currents that come in and out through the passes and
with the winds can sometimes create interior storms.

[{Image src='01_rangiroa.jpg' caption='Blue Lagoon. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

This indeed happened on my catamaran trip when we had one and a half
meter high waves within the lagoon. This made it very difficult when we
wanted to pack all the photographic gear from the catamaran into our
rubber dingy, or when we wanted to get back on board. But these waves
were very much fun to ride with the boat, just like surfers ride with
their boards the waves, you can do the same with an engine propelled
dingy, provided you have an expert and crazy captain, Teahui, like I
did.

When I tell my friends about Rangiroa and other Polynesian atolls, they
often ask me what is exactly an atoll. In 1842, Charles Darwin explained
the creation of coral atolls in the southern Pacific Ocean based upon
observations made during a five-year voyage aboard HMS Beagle from 1831
to 1836. Accepted as basically correct, his explanation suggested that
several tropical island types: from high volcanic island, through
barrier reef island, to atoll, represented a sequence of gradual
subsidence of what started as an oceanic volcano. He reasoned that a
fringing coral reef surrounding a volcanic island in the tropical sea
will grow upward as the island subsides (sinks), becoming an "almost
atoll", or barrier reef island, as typified by an island such as
Aitutaki in the Cook Islands, and Bora Bora and others in the Society
Islands.

[{Image src='02_rangiroa.jpg' caption='Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

The fringing reef becomes a barrier reef for the reason that the outer
part of the reef maintains itself near sea level through biotic growth,
while the inner part of the reef falls behind, becoming a lagoon because
conditions are less favorable for the coral and calcareous algae
responsible for most reef growth. In time, subsidence carries the old
volcano below the ocean surface and the barrier reef remains. At this
point, the island has become an atoll.

Atolls are the product of the growth of tropical marine organisms, and
so these islands are found only in warm tropical waters. Volcanic
islands located beyond the warm water temperature requirements of
hermatypic (reef-building) organisms become seamounts as they subside,
and are eroded away at the surface. An island that is located where the
ocean water temperatures are just sufficiently warm for upward reef
growth to keep pace with the rate of subsidence is said to be at the
Darwin Point. Islands in colder, more polar regions evolve toward
seamounts or guyots; warmer, more equatorial islands evolve toward
atolls, for example Kure Atoll.

[{Image src='03_rangiroa.jpg' caption='Blue Lagoon. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

The atoll formation can be followed on the example of many islands in
Polynesia: Tahiti is a relatively young volcanic island. You see
everywhere the black sand on its shores and the whole shape of the
island is that of a classic volcano. Yet the formation of the reef can
already be seen: at most places Tahiti is surrounded by a fringing coral
reef. At some locations this reef has an opening, a so called "pass".
These passes form always opposite locations where little rivers or
creeks flow into the sea. The freshwater content is not tolerated well
by the reef building creatures, so an empty space remains and it serves
also as a channel out to the open ocean. Lucky for boats!

[{Image src='04_rangiroa.jpg' caption='Blue Lagoon. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

After many millions of years, the erosion wears down the central part of
the island, and you get an island like Bora Bora. Even later you will
have a formation like the Gambier islands, which are actually the
remnants of one big volcanic island, a sort of huge Bora Bora torn apart
into fragments. Even later the central part of the island disappears
completely, after 50-60 million years. All is left will be the
necklace-like ring of the outer coral reef. Just like Rangiroa, which is
one of the biggest such atolls in the world. Hard to imagine that there
used to be a majestic volcano where we are now riding the waves of the
inner lagoon. Rangiroa preserved its two main passes: Tiputa pass and
Avatoru pass. These are the locations where major rivers used to flow
out. And of course these are the places where water masses can commute
between the lagoon and the open ocean. Entering Rangiroa's lagoon during
the phases of incoming high tide or exiting low tide is always a
dramatic experience. Massive currents and
cresting waves are not for the faint hearted.

[{Image src='05_rangiroa.jpg' caption='Avatoru Pass. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

Rangiroa offers some of the best dives in the world in and around the
Tiputa Pass, which lies at one end of the one main road and runs 3.5 km
to the Avatoru Pass. Sedentary common bottlenose dolphins (Tursiops
truncatus) regularly play group in the Pass. They can be viewed from the
mainland but it is also one of the few places where they can be
approached in scuba diving.

[{Image src='06_rangiroa.jpg' caption='Dolphin. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

Because of its large size and the existence of only two passes, each
high tide creates a strong incoming current while each low tide creates
a strong outgoing current in those two passes. When the current is
flowing inward through Tiputa Pass, about 200 shark specimens gather at
the entrance to the Tiputa Pass, at fifty meters deep. Led by the strong
current, sharks can remain motionless and allow divers to observe them
without any difficulty. Large manta rays, green sea turtles, and
humphead wrasses can also be seen. Occasionally, tiger sharks and
hammerhead sharks can also be spotted. In January, large number of
stingrays gather in the Tiputa Pass, as well as hammerhead sharks that
feed on them.

[{Image src='07_rangiroa.jpg' caption='Blacktip sharks. Blue Lagoon. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

A notable site in the atoll is the famous Blue Lagoon, which is a
smaller lagoon formed on the southwestern edge of Rangiroa. Its shallow
waters accentuate the bright blue color of the water. It serves also as
shelter to many juvenile blacktip sharks.

[{Image src='08_rangiroa.jpg' caption='Blue Lagoon. Rangiroa, French Polynesia\\© [AirPano|https://www.AirPano.com]' alt='' width='900' popup='false'}]

\\ \\
[9 panoramas of French Polynesis. Part IV. Rangiroa|Geography/Territories_Oceans_and_Islands/French_Polynesia/Pictures/Rangiroa]

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