The life and death of islands

Out here in the Pacific geology isn’t something theoretical that happened in ancient times, but even to the untrained eye an obviously ongoing event. Continental plates are moving, the sea bottom rises and from a depth of about 3000 m a new, actively vulcanic island rises (like Fernandina at the western end of the Galapagos archipelago). The ragged cliffs rise higher and higher, developing a lush vegetation on the fertile soil, while the ocean crashes unhindered against the shores (like in the Marquesas). In tropical seas corals start to grow around the island at some point, forming a protective fringe reef with a calm lagoon inside (like in the Society Islands). After some time the high islands start sinking down into the sea again, leaving only the peaks of the mountains as islands, while the fringe reef becomes an outlying barrier with motus on top (like here in the Gambier). At some point the mountains disappear entirely, leaving only a coral ring with some motus behind ( like in the Tuamotus). Sometimes the bottom rises under an atoll, lifting the coral shelf high up (like Henderson Island in the Pitcairn group). The fringing reef of the Gambier is sinking slowly back into the sea, in the east and south it’s completely submerged already, only in the north it’s still a continous motu barrier. The stormy Pacific batters these small oases in the vast ocean continously. We were very surprised when we returned to Tauna this summer (our first and still one of our favourite motus) to find the sandbank gone (it had previously stretched out a few hundred metres from the island) and the motu itself ragged and considerably smaller. A severe storm has caused that damage in spring. Remember the eulogy blog for our dinghy that was murdered by a freighter in Tahiti and the adjoining picture of it sitting on a sandbank? Well, that’s exactly this sandbank and it must have left the surface of the sea at approximately the same time as our dingsi did… We asked our friend Herve, who grew up in the Gambier and he remembers more motus that have disappeared since his childhood, so geology really happens within a short time here (about 30 years ago). We’re now back in Tauna, enjoying the shrunken, but still gorgeous motu with its colonies of white terns, noddies, greater crested terns, some red-footed boobies, and frigate birds.

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